GlobalFoundries Thomas Barber: CPO, Silicon Photonics, 300mm, SiGe, OCI, NRZ

0:04Hello, everyone. Today, we have a special guest, Tom Barber, VP Communications Infrastructure and Data Center at Global Foundries. Hey, Tom. Good morning. How are you? Good, good. Thanks for coming. So today, I want to talk about Global Foundries and your photonics and optics sort of background and experience as a company. I don't think most people think of Global Foundries when they hear CPO or when they're thinking about photonics. So I thought you'd be the perfect person to talk to on this topic. So let's jump in. So I think right away when I heard Global Foundries in this space, I thought, wait, Global Foundries does photonics?

0:47So most people probably like me know Global Foundries as the foundry that was in the running at the leading edge for a while and then step back and start focusing really on foundational nodes. But what people like myself don't know is that you actually do have a background in the business of moving data with light, and you have for well over a decade. I think it traces back to the IBM microelectronics business. So maybe start very high level for us. What does Global Foundries even do in photonics? How far back does it go? Just educate us. Sure. Sure. Yeah. And I think, you know, Global Foundry's focus is really on what we call essential silicon.

1:26Right. And that's the foundation of all electronic systems, you know, including data centers. Right. It's power. It's communications. You know, it's memory. It's all the things that are essential to making these communications, these electronic systems work. And silicon photonics perfectly aligns with that strategy. You know, it's very differentiated. It's very complex technically. And it's in a very challenging market. Right. So there's a great opportunity to differentiate. For those people that don't know, Global Foundries, we were born out of AMD. We were the AMD foundries that were spun off.

1:59But over time, we acquired both Charter and Semiconductor, which had a silicon photonics effort, and we acquired IBM Microelectronics, which has a long history in silicon photonics. The effort at IBM Microelectronics actually started in the mid 2000s with doing very basic integration of waveguides, modulators and photodiodes into CMOS technologies. In the mid 2010s, so after about 10 years of effort, that turned into real products shipping, you know, 25 gig per lane type of products shipping in mass volume. The volumes were fairly small at the time because it was really only used for long range point to point communication.

2:36but we've continued to invest and now we're on our third generation of integrated silica photonics and that's really what's being rolled out in mass scale in the data centers today so interesting okay so the history traces back you got amd and acquisitions of chartered semi and ibm microelectronics that's super interesting and yeah it sounds like you've been in this uh long distance optical communication space so i did not know that now what also surprised me is I'd heard recently that Global Foundry claims to be the largest pure play silicon photonics foundry by revenue. And again, I think people think of TSMC Coupe or they think of Tower Semi.

3:16And again, that's kind of like a shocking fact. So can you maybe tell us a little bit more about like, is that true? And tell us a little bit more about the business. Yeah, so that is true. I think that's really, you know, we have been working with key customers for a very long time, right? And growing as the business grows. And that's been key to us to make sure that we have those strategic customers in place that are the market leaders. The second piece of this is we made a very early investment in moving silicon photonics to 300 millimeter foundries, right? We put it into our facility in Malta, New York.

3:53And that's been huge for us because it has allowed us to significantly expand our capacity. And that's what the market's looking for as much as anything right now is everybody's just desperate for more capacity, and we are available to provide that capacity. As a part of that, we added the AMF team in Singapore, which brought in a full range of very highly differentiated products that were actually orthogonal to what GF was doing. GF's primary focus was on short range and data center products, where AMF was doing a lot of business in long range. And so that helped us round out our portfolio and added a complimentary set of very high value products.

4:32And the combination of the GF silicon photonics business plus the AMF business is what made us number one by revenue. Ah, okay. Okay. So there was the short range play and the long range via the acquisition. One interesting thing going back a little bit, you said moving to 300 millimeter wafers. Can you explain that more? Like was that coming from 200 millimeters to 300 millimeters? And why is that such a big deal to unlock more capacity? Yeah. So yes, most silicon photonics today is actually still produced on 200 millimeter wafers. That's where most of our competitors are. When you go to a 300 millimeter wafer, you know, it's the radius squared, right?

5:12So you go up by 50 % of radius to square that, you know, you get 2.25 times as many dye per wafer, right? So running the same number of wafers, you get more than twice as many units coming through. And that's really important as we scale you know photonics even going back five years was a relatively small business right for two reasons one is you know there were other alternatives indian phosphide and eml that were very competitive at 50 and 100 gigabits per second plus you know the overall market was just significantly smaller the data center piece had not really taken off yet but the data center piece taking off and 200 gigabits per second being the node that's really taking off that's the optimal place for silicon photonics and that's why we've seen an explosion in silicon photonics so having that extra volume available via 300 millimeter wafers is really helpful yes okay so let's talk more about this 200 gigabits per second and sort of the opportunity right now um for uh optics and and maybe let's talk like scale up um so i know you know early rack scales ai systems the switch was at the top of the rack you had like eight gpus interconnected and nodes and they were connected to a switch at the top of the rack but um as these racks are getting denser and we've moved to 200 um gigabits per lane speed now all of a sudden um i think it's difficult to get the i know the switch has moved to the middle of the rack because it's harder to reach from top to bottom so like unpack the problem that the industry is trying to overcome right now?

6:49Yeah. So it all comes down to the fundamental limitation of copper, which is range. Right. So at 100 gigabits per second, a direct attached copper cable, so no intelligence, just a dumb cable, could span about two meters, which is basically the height of a rack. Right. So you could go, you know, any connection within a rack, you could deal with copper without a problem. When you get to 200 gigabits per second, that range drops to about one meter, which is why when you look at like an NBL 72, they move the switches to the middle of the rack because that's kind of as far as they can go realistically.

7:23When you go to 400 gigabytes per second, now the range is half a meter and you're not going to quarter the size of the rack, right? So you have to go to something faster or something with more range, which is optical. That's really kind of the high speed stuff. And that's within a rack. Now, right now, most of the scale up networks are within a rack. So an NBL 72 is one rack. The Helios that was just announced by AMD is a single rack. But you really want to go to multiple racks. And when you go to multiple racks, now you're talking about spanning tens or even hundreds of meters. And that's when you absolutely have to switch to optical.

7:58You cannot do that with copper, not at the speeds we want to do. Okay. So for scale up, you're saying that copper is getting shorter and shorter. And so one way to move forward is to just try to move the switches closer and closer to the GPUs, but ultimately that's going to run out of steam. So even within the rack, you might need optics. But then of course, the question is why stop with one rack? Why not have a scale up domain that could stretch into neighboring racks or four racks side by side? And so of course, now it was about like shrinking, but then it's about expanding as well. And you're saying that only optics can pull that off.

8:35Yeah. If you look at what Google has done and even what Huawei has done with their scale-up networks, they've gone beyond a single rack. So instead of being limited to, you know, 72 or 144 GPUs, depending how you count them, you know, they're doing 300, 500, 1 ,000 GPUs across, you know, 6, 8, 10 racks, right? So they're really expanding the size that are scale-up networks using optical communication to span multiple racks. Gotcha. Okay. So then walk me through, are we talking about like pluggables for the optics or NPO or CPO? And where does Global Foundries come in? Right. So it can be any of those options.

9:18What we see is a trend from pluggables, first going toward NPO and then towards CPO. And the reason is really cost and power and density. So when you're at the edge of the rack with a pluggable, you're looking at about 35 dB of loss from the edge of the rack to the CPU or switch ASIC in the middle of the server. That loss has to be compensated for by a kind of expensive and pretty power-hungry DSP in the pluggable. When you move to an NPO system, now you've dropped your loss from about 35 dB to somewhere between 15 and 20 dB. That allows you to significantly reduce the amount of compensation you need to do on the electrical side or even eliminate it.

10:08So if you have enough link budget end to end that you can handle the extra 15 dB of loss on either end due to the transition from the NPO to the core processor, then you can get away with not having a retimer in the npo which is what most people are doing they're doing what's called linear and so that removes that dsp from the system which saves a lot of cost and saves a lot of power but you still have a fairly bulky package for this npo and what you want to do and you still have a lot of loss in the system right there's still 15 db of loss it needs to be compensated for if you continue to co-package the optics and you move that transition from electrical to optical into the package now you've dropped your loss from you know 15 db down to like 6 db and that really helps you both from the link budget obviously because you've gotten yourself an extra 20 db but that also allows you to lower the power of your 30s significantly right so we're trying to do is we're trying to minimize the number of picodoules per bit that you need for the communication so when you're pluggable you're talking about you A fully retimed pluggable is somewhere around 20 to 25 pJ per bit.

11:22When you go to NPO, you can go to linear and get rid of the DSP, which does a lot. It gets you down to maybe 10 pJ per bit. But you still have a pretty powerful certes to overcome that 15 dB of loss between the core processor and the NPO. When you go onto the package with the GPU or the ASIC, now you're talking about 3 dB of loss. And now you can go to the lowest power 30s, which allows you to get down to less than five picot joules per bit. Now, that's really critical because all of these systems are thermally limited. So every picot joule power that goes into the communications is one you can't use compute.

12:04So what you want to do is minimize the amount of power that you use for the for the communications between the GPUs. So you can run the GPUs as fast as possible. sure okay so if we orient around power the goal is to in a gift given a fixed power budget in this data center it's only got 50 megawatts or 100 megawatts whatever we want to use as much power as possible for compute and as little as power as possible for communication sending data around now talk us through again why kind of zooming back out um you talked about pluggables why do they have so much loss in them you talked about they have a dsp but like where does the loss come from because i think people it's not in the optics right it's like the electrical trace yeah it what it is it's it's the it's the electrical traces through the pcbs from the core processor you know a couple hundred centimeters to the edge of the server right and so those are very thin wires um and when you're talking about you know a 200 gigabit per second PAM4 signal has about 55 gigahertz of bandwidth, right?

13:12So you're trying to run a 55 gigahertz signal through a very long trace on a PCB, and you end up with a lot of loss. So then a step in the right direction, NPO, near pluggable optics, you're ultimately shortening that trace, and then finally co-package optics, maybe you're getting rid of it entirely. But can Can you walk us through the trade-offs of, you know, why doesn't, I know people are talking about using NPO as a stepping stone to CPO. So can you talk us through, like, why not just jump to CPO if it's the most power efficient? Right. So the concern with moving away from pluggables is reliability.

13:57right so right now optical communications in general is seen as a reliability risk and so the data center customers are very comfortable with it being pluggables because if something goes wrong they just swap the pluggable right just take one out put a new one in and move on they don't always do root cause to ensure that the pluggable is really the problem but if you swap out the pluggable and the problem goes away then you're fine you keep going Moving to near-packaged optics is a half step in the right direction. Those solutions will probably be socketed, so they'll still be relatively easy to maintain.

14:35You'll have to open the server and swap it out physically, but it's still something that can be swapped in place without completely replacing the GPU. When you go to co-packaged optics, now you're talking about something that is permanently attached inside the package of the GPU. so the reliability has to be extremely high. So data center customers, Meta in particular, are going through the effort to validate the reliability of those solutions right now. And Meta's released a couple versions of a study that they've had running for a long time with 50 ,000, I think it is, GPUs in a network using co-packaged optics.

15:13And what they found is the reliability is actually higher than it is with pluggables. And they found no link flap, which is the primary cause of concern in optical communications across their entire testing range, which I think is up to 50 million hours or something like that right now. So, you know, they're doing the work and becoming more comfortable with the reliability, but they're not going to deploy it at scale until they're absolutely certain that it's a reliable solution. Fascinating. So tell us why are people expecting that the reliability is not great for CPO and then finding out from meta like oh actually it's not as bad as you think i mean is this about like is the laser is it a external laser and the concern was that the laser sitting near a hot chip but that's not a problem or or what is the problem that people think should be happening and maybe it's overblown i think it's problems that are actually happening today because you know and And again, there's not great.

16:12Meta's actually done some good work on this in root cause. But, you know, the things that end up causing problems in optics, some of them are actually due to the fact that it's pluggable. Right. Because you're plugging it in, there's the opportunity for dust to get in the connector and block the optical signal. Right. So when you're swapping out a pluggable, if dust gets in there, all of a sudden you have a reliability issue. Right. And it's attributed to the pluggable, but it's not the inside case of the pluggable. it's a problem really it's the fact that the pluggable you know there's something interfering between the pluggable and the and the connector so when you go to cpo and you have a fully integrated solution you know that's done in a clean room facility right there's no dust there right when you have things that are permanently attached or semi-permanently attached you know you're not dealing with these connection issues that you get where reliability concerns appear so So that's what the hyperscalers are really trying to become more comfortable with is not that CPO will be as reliable as pluggables.

17:09That's not good enough. CPO has to be way more reliable than pluggables. So I don't think anybody questions that CPO is as good as pluggables. The question is, is it so much better than pluggables that it can be made a permanent part of the system? Gotcha. Sure. Fascinating. So it's almost how surprising if the idea was like, oh, yeah, pluggable is like the release valve where if there's a problem, you can unplug it and put something else in. But actually, what if the problem is the pluggable, the act of plugging it in itself? It's kind of funny. So, yes, if you can make something co-packaged in a clean room facility, maybe dust never gets in and you actually don't see those issues.

17:47That's really fascinating. So then what about like cost? I mean, everything has a tradeoff. So if CPO potentially has great reliability and it's much lower from an energy cost, what about like dollars and cents? Is it more complicated? Is it expensive or is it all a wash compared to like linear or traditional pluggables? Yeah. And again, it comes down to if you look at a pluggable, you strip away a lot of the components of the pluggable when you go to co-package optics, right? You obviously don't need the case anymore. That disappears immediately. There's a lot of support circuitry on there, some MCUs, some power, and in particular, especially the DSP that goes away.

18:36So the DSP is probably the biggest component that goes away from a cost standpoint. So that saves you a lot of cost. And then you get into the operating costs. And when you have a significantly lower power, that obviously translates directly to operating costs. interesting okay so um let's move on a little bit so i saw some news about uh the oci msa like a multi-source agreement for optical interconnects so can you enlighten us like what is an msa what is this and why does the industry write one i think that some of the names involved amd broadcom nvidia meta microsoft open ai so like all all it seems like everyone is a part of this.

19:20Why is this necessary? Yeah. So an MSA is a multi-source agreement. And what it is effectively is the industry looking at a standard, typically a standard from the IEEE, and saying, okay, this is great, but there's a lot in here that maybe is options. And what we're going to do is we're all going to agree on, here's the options we're going to do. Here's the options we're not going to do. Here's how we're going to test things. Here's how we're going to make sure it's interoperable you know so that is is what an msa is the one that's it's not called an msa but honestly the most famous msa is the wi-fi alliance so the wi-fi alliance takes the wi-fi spec from ieee and turns it into something that can be productized right the optical industry is typically at msas focus primarily around mechanical so if you look at the you know there's one for it's called OFSP.

20:14That's the form factor for the pluggable. So it defines the mechanical electrical interfaces so that when you plug these things in, they all work, right? The electrical interface is defined by OIF and the optical interface is defined by IEEE. But the MSA kind of brings all those things together and says, okay, here's how we're going to combine these pieces and wrap them up mechanically such that we have a interoperable pluggable. The OCI MSA is a little bit different in that it's actually taking and defining the optical interface, right? So that, for most of the optical communications used in data centers, is defined by IEEE, IEEE 802.3.

20:54That is not sufficient for what we want to do for scale-up compute, right? And OCI is really focused on scale-up compute. And so when you look at the participants, the founders of OCI, they are the key suppliers in the data center industry. They know absolutely what is the best solution for scale up networking. Right. And so they've come together and said, hey, listen, the specs, the optical specs that the IEEE is defining are not really fit for purpose for the scale up application. This is what we believe is fit for purpose for the scale up application. This is how we think you should do things.

21:32and it's really focused around maybe not going as far range-wise because you know two kilometers maybe is a little too far for for a scale-up network so we're going to back off on that a little bit and we're going to go to a wide slow solution and what that is is you know the to go as fast as possible with as much data as possible over a single fiber IEEE has moved to multi-level modulation. So it's called PAM4. And you transmit two bits per symbol and you have four levels. And the issue is those levels are pretty close together. So you have to either have a lot of power or very low noise to receive them properly.

22:12What they've done with OCI, they've gone back and said, we're going to go back to a binary system. So only one bit per symbol. And we're going to slow it down to 50 gigahertz. But we're going to do four wavelengths per fiber. So we're going to take advantage of the fact that you can put multiple channels on a single fiber to still have that 200 gigabits per second of bandwidth, we're just going to do it with four wavelengths. And what that does is it makes the receiver a lot less complex. So the amount of channel equalization you need goes down quite a bit. And the amount of forward error correction you need goes down by quite a bit.

22:48The native bit error rate for NRZ 50 gigahertz is about a million times less than what it is for PAM4. So it's significantly easier to receive an NRZ signal. And that translates into reduced costs, and it translates into reduced power. Oh, fascinating. Okay, so the industry is coming together, saying we're going to make an interoperable standard. And presumably, that's just so that there can be competition so that everyone can say, hey, we're building to this spec collectively. And then what I heard you say, which is fascinating is it sounds like the industry is aligning around not just trying to continue to increase the per lane speed and double it, double it again, but actually to like walk back a little bit instead of Pam Ford, go back to NRZ and say, hey, let's go back to 50 gigabits per second NRZ, but can we send four like wavelengths down the same fiber, kind of four colors, if you will.

23:48And those are being sent simultaneously. Correct. Yes. Interesting. So So if there's different wavelengths being sent simultaneously, is that like a boon for people that make the lasers? Do you need more lasers to do that? So just back up one second, just to explain something about the difference between the scale-up application and the scale-on application. So the scale-up application, what you're trying to do is you're trying to connect as many GPUs as you can using a single hop network. right and so if you look at the maximum size switch you get today is 100 terabits per second and so at 200 gigabits per second per fiber you can connect 512 gpus to each switch right and then what you do is you stack up switches to give you the most bandwidth so if you look at the nbl 72 system they have 18 switches in parallel which allows them to get to that 7.2 terabits per second bandwidth they have per GPU.

24:47But each fiber is only, or in this case, they use copper, each copper pair is only 200 gigabits per second. It's just shared over 18 switches. The other thing that the OCI team has done really well is, so when you look at the amount of lasers you need, it's not as simple as one laser per wavelength, because the laser power can actually be split and used by multiple fibers right so if i have a transceiver that's got eight fibers connected to it i typically right now the ratio is four to one so i'd have two lasers to drive those eight fibers but for plugables it's actually moving to eight to one so you'd only have one laser driving all all eight of those fibers with the oci spec they've backed that off even further so you can get to as extreme as 32 fibers per laser so one laser could drive 32 fibers so you could get a full optical engine solution with the eight wavelengths of light that's needed for OCI with just eight lasers.

25:45Gotcha. Okay. And then you were saying that we don't need to think about like one laser per port or anything like that. In fact, the laser, the light can drive many different fibers, maybe up to as many as 32. Correct. In like the most extreme case. That's pretty cool. Okay. So now tell about where does Global Foundries come in here? I know you guys announced scale and you called it the first OCI capable platform. So tying back to that MSA, can you explain a little bit more about scale and, you know, how you're the first OCI capable platform? Sure. So what we're doing with scale is we're putting together everything you need to do the electrical to optical translation in a known good form factor, right?

26:31And call it a chip light, color module, whatever, right? And so what that includes is it includes an electronic IC, which is going to be used to communicate to the CPU or the GPU or the AI ASIC. And then that electronic IC sits on top of a photonic IC, which does the translation between electronic and photonic signals. That photonic IC has a detachable connector on there. And that detachable connector is key because when you're assembling a CPU, what you don't want to have to do is have a fiber dongle hanging off your your photonic ic at all times you want to create you know you want to build your server using rectangles right and then plug everything in at the end and so with that detachable fiber connector it looks very much like copper where you build all your pcbs put them all together and then you have a wiring harness in this case an optical wiring harness instead of electrical wiring harness that you connect at the end that bridges from those cpo modules connected to the gpu to the edge of the server and global foundries you you can fabricate which of those pieces do you guys fabricate and assemble yeah so we have the ability to manufacture all of it um the photonic ic for sure we do 100 of the manufacturing we have a number of different design partners working with us on photonic ic designs.

27:56The electronic IC, it really depends on the complexity of the design, particularly digital. So if it's a less complex design, we can use our FinFET process or one of our FDX processes. If it's a simple linear translation, we could actually use our silicon germanium process even. If it's a more complex digital translation and a customer wants to use an advanced node, like a three nanometer or two nanometer node, then they're free to do that and we'll bring that wafer in and do the assembly and test. The micro optics, again, are manufactured externally, but we do the assembly and test on that. And so we deliver at the end of the day is a known good, fully tested module with very high reliability.

28:38Okay, fascinating. So then talk to us more about like, position yourself against what some other people are doing. Like I know TSMC is in this space with coop and they use a grading coupler and i think global foundries uses a different technology and edge coupler and could you maybe explain a little bit more about the technology differentiation that and the approach you're taking right so we do so yes the mechanism for the light getting into the wave guides is very similar to edge coupling but we use we don't do it at the edge of the die, we actually have a micro mirror that we implant into the wafer.

29:20So the light can still come in vertically, right? So the light comes in vertically exactly the same as you would with a grading coupler. We just have a mirror and that reflects the light horizontally into the waveguides on the photonic IC. The reason we went with that approach instead of grading couplers is because grading couplers inherently have limited bandwidth. And so you can't service the entire O-band with a single solution. With a micro mirror, we can do the entire O-band, which gives us the maximum flexibility as far as doing the wavelength planning, right? So OCI today is four wavelengths in each direction.

29:55You know, one of the ways we're going to scale that to do higher bandwidth is to add more wavelengths. And so as we're thinking about how do we evolve into the future, we wanted to make sure that we made the entire O-band available to use for as many wavelengths as possible. Ah, fascinating. And for listeners who might not know, can you define like, what does O band mean? Yeah. So the O band is, you know, you think about AM FM bands for your radio. So O band is an optical band. It's around 1310 nanometers, which I can't divide by the speed of light in my head to figure out how many gigahertz that is, but it's really, really fast.

30:31Gotcha. Okay. Thanks. That's helpful. All right. So then, okay. So you guys are taking a different approach and you think, you know, it keeps the whole O-band on the table, which will be helpful in the future as you're trying to increase bandwidth, it will keep more wavelengths sort of at your disposal. At the end of the day, you know, I see people online and they'll say, you know, oh, this one company is better than the other. But it feels like a little bit sort of like armchair quarterbacking. Like, like, can you help us understand as people interested in the space, like, how do we know, as a non-engineer, you know, non-silicon photonics engineer, how do we know how good, you know, Global Foundry's components are?

31:12Is there like a good proxy or a good way to understand? Is it just like looking at the customers or what do you think? Yeah, I mean, that's the, you know, the market doesn't lie, right? So, the market will choose the best solution, right? And so, that's, you know, we're at the very beginning in this market. And like I say, right now, you know, So TSMC, other foundries, they're not the enemy to me, right? The enemy to me right now is copper. I'm trying to beat copper, right? If TSMC wins and we win, that's great because we're both displacing copper. And until all the copper is gone, there's plenty of market to go around.

31:44So, but from a standpoint, yeah, how are you going to tell from the outside? You know, you will see customers adopt certain solutions and that's going to tell you who's got the best solution. Gotcha. That's helpful. So then also one other thing, I think I saw in a press release somewhere about scale mention of known good dye testability. Can you explain that a little bit more for listeners? Yeah, and known good dye is probably under calling it. And I mentioned earlier, it's known good, very, very high reliability dye. So with known good dye, what we're doing is making sure that what we deliver to our customers is 100 % functional.

32:26right and that's a very complex process because we're looking at a solution that has electrical signals on the bottom so you can connect it to the substrate or the interposer and the optical signal coming in from the top so normal electronic test is only one-sided you you drop your pro pads on and you test things and you pull it off we've got to do a two-sided test right we've got to take light in from the top we've got to put electrical signals in from the bottom we have to test that at high speed because we're talking about signals at 200 gigahertz coming in and we've got to test a lot of channels because these optical engines you know a normal plugable transceiver right now maxes out at 1.6 terabits per second these optical engines are going to be 7.2 14.4 even higher right so we're talking about a lot of bandwidth that has to be done in parallel so we've put a huge effort into you know building test systems that a can connect top and bottom and b have enough bandwidth to do this full testing and so we'll deliver that known good optical engine to to the gpu provider or the asic provider and they'll integrate that onto into their package very very similar to how they would do an hbm today or an iodite today right that's and then And that testing gets you to, you know, time zero reliability, right?

33:43Time zero yield. But now you have to have reliability, right? You need this to survive in a very, very extreme environment for a very long time, right? You can't fail in the field. You can have zero failures, right? So beyond just the kind of time zero testing and make sure it works, you know, the first time you plug it in, we need to make sure that it works for 10 years plus under very extreme circumstances, right? And that reliability testing is actually key to success long term. Nice, that makes sense. Interesting. So when I'm zooming out, and I'm thinking about, you know, the technology you have the ability to offer the pick the photonic IC and the electronic IC, or package that in from someone else and do all the coupling.

34:34And then of course, we're talking about scale up where this feels like it's going to be a very large TAM because just there's your have the opportunity to connect lots and lots of GPUs. So there could be lots of optical engines, lots of fibers, big opportunity there. Like, what are you guys saying publicly about how big you think this market is and how much opportunity there is for global foundries with CPO? Yeah, I mean, if you look at the scale up bandwidth compared to scale out, right, the scale up bandwidth is somewhere between five and 10 times what scale out is, right? And the scale up today is all copper.

35:17So if we can convince everybody to move their scale up networks from copper to optical, you know, we're sort of instantly talking about increasing the size of the market by 5x or 10x, That's why I say the enemy is copper. It's not other foundries. We want to enable that conversion. We want to work with other people. We want to partner everything we can to convince the market to move from copper to optical for scale up. And because it's the right solution. So that opens up a huge potential market. So if you look at, I can't remember what the latest projections were from LightCount or Signal AI, but tens are close to 100 billion in optical.

35:53you know think of that market going 5x 10x bandwidth now it's not going to make the market go 5x or 10x because like i said the the cpo solutions have to be much more cost effective than what you're looking at for pluggables but you know doubling easy 4x maybe and then pile on top of that you know the bandwidth continues to increase you know the number of servers continues to increase. So, you know, it's a very high growth market for a while. That's promising. That's exciting. Okay, one other topic, you mentioned silicon germanium in passing. And I think I saw on your most, not today's earnings call, but the most recent one before that, a quarter ago, mention of silicon germanium capacity in Vermont being oversubscribed.

36:41And anytime I hear something oversubscribed, you know, my ears kind of perk up. So can you tell us Like, what is the silicon germanium used for? And like, yeah, enlighten us a little bit. And why is it in such demand? Right. So when we're looking at optical transceivers today, there's two components that are used to locally on the pluggable or even between the pluggable and the GPU to amplify the signal coming into or going out of the photonics, right? One is the driver, which is a it's a modulator driver. So it amplifies the signal coming out of the DSP such that you can drive the modulator that's the silicon photonics modulator on the PIC.

37:24That, to some degree, is being integrated into the DSP. So the market's shrinking a little bit on that. The other one is a transimpedance amplifier. So that takes the current out of the photodiode, which detects the incoming light, and translates it into a voltage, which is then converted and processed on the DSP. the bandwidth of those is similar to what i talked about earlier with the pcb you know for a 200 gigabit per second pam4 signal you're talking about 55 gigahertz of bandwidth if you've got a retime system and closer to 70 gigahertz of bandwidth if you're trying to do a linear system typically for an amplifier you need about the transistor speed needs to be 5x what your bandwidth this right so now you're talking about transistors that need to run 350 400 gigahertz to do the 200 gig per lane we talk about 400 gig per lane now you're talking about doubling that right so you're talking about transistors that are 600 700 gigahertz very very few companies can do that at scale and reliably and silicon germanium from gf is one of those few technologies right so we have you know Very, very good silicon germanium technology.

38:32Our transistor speeds are extremely high, much higher actually than what you need for 200 gig per lane. And we have new generations, you know, roadmap to support 400 gig per lane very quickly. So, you know, we've been fortunate that we've gotten a lot of adoption on 400 gig per lane. So as you see the 1.6 T transceivers volume increasing, you know, we're getting a disproportionate share of that right now. Okay, interesting. So Silicon Germanium is about transistor switching speed. And as we see switching speeds or bandwidths of like 200 gig, 400 gig, it means we should think Silicon Germanium and we should think global foundries.

39:13Yes. Fascinating. Awesome. All right, Tom, we've covered a ton of ground. It was pretty technical, but I appreciate you walking us through and teaching us and enlightening us also about Global Foundries from a business perspective. So thanks so much for your time. Thank you, Austin. It was great talking to you. I appreciate the time.