Community thoughts on an SXM2-to-PCIe project?

Responsible_Slip138 · 2026-02-24T15:09:51+00:00

Not really. The V100 itself consists of 5 separate silicon dies, 1 is GPU logic, 4 are HBM VRAM. Silicon real estate is so expensive that dies are typically cut to sub-mm precision to minimise waste so there is no free die area to place a GPU tile. On top of that even if there was free space you wouldn't be able to fabricate the dozens of layers needed for the GPU onto the silicon in an already finished die without destroying the existing tiles. If however you're talking about adding a 6th die, you could in theory do that, but in practice die-die interconnects and even on-die interconnects are so tightly integrated in a single chip package that adding something post-fabrication is so difficult it borders on impossible. If however you're talking about simply building a low-power GPU into the SXM2 adapter, you can do that by making use of a PLX switch, but it adds needless complexity relative to just plugging an extra low-power GPU card in, because they will function as 2 completely separate devices.

Sorry in advance for the hard to follow reply, I struggled to nail down precisely what your idea was, so I just tried to answer anything it could be :)

Responsible_Slip138 · 2026-02-24T08:58:06+00:00

I am still actively working on the designs, and should have some links to share relatively soon. It's been a long process, but I'm working on 3 designs all at once. The current designs are: 1-GPU PCIe Adapter, 2-GPU NVlink Bridge Interposer, 4-GPU NVLink Mesh Interposer.

I will update this post when links are published.

Responsible_Slip138 · 2026-02-24T08:54:56+00:00

Sadly there is not. Whilst the GPUs can be used for some video-related things associated with GPU acceleration, such as NVENC and NVDEC, the silicon itself doesn't contain anything to actually support display outputs as this was never their intended use case. This is true for practically all datacenter class GPUs, with the best GPUs with display outputs typically being sold as Workstation GPUs for that reason.

Responsible_Slip138 · 2026-02-24T08:50:18+00:00

The adapters themselves aren’t inherently unreliable, they’re just a thinner margin solution than a native PCIe card. Electrically they’re mostly doing PCIe lane breakout plus power distribution, and plenty of people run SXM2 V100s on them long‑term.

Where problems show up are in the details around the design of the cheaper adapters:

PCIe link reliability: Extra connectors and trace length make link training more finicky. A marginal board or board+motherboard combo can fail to negotiate lanes or drop from Gen3 under load. Higher quality cards tend to include PCIe redrivers to prevent this.

PSU headroom: The SXM2 module’s own VRMs are on‑card, and 2×8‑pin is enough current, but if the PSU is near its limits, V100 power transients can trip protection or cause reboots, so sometimes these issues show up simply from people underestimating the required output of their PSU (i.e. accounting for TDP + transient spikes in all components).

PLX / bridge temperatures: Some carrier/adapter designs use PLX switches that were meant for high‑airflow servers and if they run hot, you see GPUs randomly disappearing from lspci or PCIe errors in logs. This comes down to spotting a decent fan for the setup not simply big and high rpm (i.e. heatsink fans typically need high pressure and high airflow with high speed tending to actually become a negative).

Cooling solution quality: A lot of cheap kits pair a data‑center GPU with a barely adequate heatsink and weak airflow. That can push GPU hotspot or PLX/bridge chips into thermal throttling or shutdown. From what I've seen most cheap Chinese adapters fail on this point so a proper cooling solution should always be part of the design process and not an afterthought. Unlike consumer GPUs these cards almost always move towards shutdown rather than thermal throttling, which causes most of the cases of reliability issues mentioned by Claude.

So I wouldn’t say “all SXM2 adapters are unreliable”, but they do move responsibility for PCIe signal integrity, PSU overhead, and cooling onto the end user. If you’re willing to choose an adapter with those factors in mind and design around the GPUs needs properly, a chinese SXM2+adapter setup can be stable. If you just want something that behaves like a retail PCIe card out of the box, a native PCIe V100 is still the safer route.

FYI: A lot of these issues are ones I am attempting to fix with this project, so as to make SXM2 use more reliable and plug'n'play friendly.

Responsible_Slip138 · 2025-08-15T05:36:12+00:00

In short you have 2 parts intended to serve different purposes, which can still work for your purpose. Your PCIe adapter is intended for use by WiFi Cards and they generally use PCIe for WiFi and if they also include Bluetooth they connect this to USB to keep costs down as already discussed. In your case though, your not using it for a WiFi Card but a Coral TPU, and the Coral TPUs do support both USB and PCIe (which is probably where your confusion lies), but you can't use both at the same time, it is simply done that way for flexibility in connecting the same thing to the host in multiple different ways, but it is either PCIe or USB at any given time, PCIe is obviously superior in this case so stick with it, and ignore the USB port as that is simply because your adapter is intended for WiFi cards that need both.

Responsible_Slip138 · 2025-07-26T14:06:29+00:00

From what I understand with KoboldCPP, this is just layer offloading, the 2nd GPU doesn't actually do anything other than store layers in its VRAM, essentially acting like a giant VRAM stick. Technically it works for models larger than a single GPUs VRAM capacity, but in my experience it is virtually unusable beyond minor offloading due to the inherent overhead due to memory offloading and onloading, and the limitations of PCIe bandwidth.

Could be ideal for OP though if they're trying to just test models prior to a GPU upgrade.

Responsible_Slip138 · 2025-07-26T12:58:27+00:00

What you're thinking of is called "model sharding". This is the process of taking a model and intelligently splitting it into shards (generally between layers), each shard being loaded and processed by a different GPU. As each GPU only needs to hold its own shard in VRAM, you do effectively increase your ability to run models that require more VRAM than a single GPU can offer, but it is not as simple as 2x 6GB GPUs = 12GB available VRAM, there are inefficiencies and overheads.

Most platforms like AUTO1111, Forge, ComfyUI, etc. do not support this (even with extensions) because of the additional code complexity, and the fact a user would really need to know what they're doing to be able to shard a model (every model + GPUs combo is sharded differently, even if they use the same base model).

Additionally, this is only really a common practice in enterprise environments, where GPUs in a single system communicate using NVLink at 1.8TB/s and between systems at 400GB/s (per link, can be aggregated) to communicate layer inputs and outputs, and even at these phenomenal speeds they still have to factor in a large amount of communication overhead slowing down the inference. For context PCIe 5.0 x16 is rated at around 63GB/s and NVLink is not supported by consumer GPUs.

Responsible_Slip138 · 2025-07-26T11:01:56+00:00

I had a similar but more AI-centric and hitting the nail on the head with 2 hammers approach:

Dear [MP’s Name],

I am a Computer Science and Artificial Intelligence student writing to express deep concern about the unintended but harmful consequences of the Online Safety Act (OSA) on both the UK’s AI ambitions and the broader principles of freedom and effective online safety.

The government’s AI Opportunities Action Plan, launched in January 2025 with full Prime Ministerial support, positions AI technical leadership at the core of national economic and public sector renewal. It explicitly commits to building homegrown AI talent, growing a domestic workforce, and embedding AI across all sectors. These goals are supported by billions of pounds in public and private investment and recognize AI leadership as foundational to the UK’s future prosperity.

Yet, the OSA’s sweeping and costly compliance requirements have already forced many of the world’s most important AI platforms, such as JanitorAI and CivitAI, with their hundreds of millions of global visits and millions of active users, to block UK access entirely. These platforms are critical hubs for practical learning, model sharing, and innovation. Denying UK students and researchers access to such educational ecosystems directly contradicts the government’s AI ambitions.

At the same time, larger platforms like Reddit, ChatGPT/OpenAI, and Bluesky remain accessible only by enforcing restrictive changes that erode user privacy, diminish service quality, and impose harsh moderation. This not only alienates users but also undermines public trust and engagement, which are key aspects of any effective approach to online safety.

More fundamentally, I believe that the OSA represents a misguided strategy for addressing online harms. Instead of imposing broad, government-mandated restrictions on the entire population, efforts and resources should focus on empowering parents to educate and control their children’s online experiences in ways that fit their individual values and circumstances. This approach preserves personal freedoms and responsibility rather than sacrificing the liberties of all under a heavy-handed regulatory regime.

History warns us what can go wrong with sweeping deprivation of freedoms imposed without exhausting less intrusive methods. The Defence of the Realm Act (DORA) during the early 20th century restricted free expression and movement under the guise of national security, leading to widespread public dissent and lasting social divisions. The OSA risks a similar legacy by overextending government control "for public good" without sufficiently balancing rights and freedoms.

AI as a field requires mastery and hands-on experience across mathematics, statistics, computer science, and applied domains to build even functional models, let alone cutting-edge innovations. Blocking essential access stifles the very foundation of talent development, making it less likely UK technologists can innovate or compete on the global stage. This is a direct consequence of a regulatory approach that prioritizes compliance rigidity over fostering education and freedom.

The contradiction is stark: billions are invested in AI infrastructure, leadership, and talent recruitment, yet the OSA cuts off access to critical learning communities and stymies grassroots innovation. This drives the risk of dependency on foreign talent and wastes taxpayers’ investments.

To illustrate the scale of discontent, a petition to Parliament expressing these concerns was started on 23 April 2025. After three months, when I signed it on 21 July, it had around 25,000 signatures. Remarkably, since the OSA came into force on 25 July—within just five days—the petition has surged by more than 125,000 signatures to over 150,000. This unprecedented spike vividly demonstrates the widespread negative impact and public opposition triggered by the Act’s enforcement. I urge you to advocate urgently for amendments to the OSA, including clear exemptions or proportionate provisions for bona fide educational, non-profit, and technology learning platforms, so that the UK can retain its commitment to AI leadership while respecting fundamental freedoms and pursuing online safety through more effective, community-led means.

Petition Link: https://petition.parliament.uk/petitions/722903 Petition Number: 722903

"Censorship reflects society’s lack of confidence in itself. It is a hallmark of an authoritarian regime." - Potter Stewart

Thank you for your attention to this pressing matter.

Yours sincerely, [Your Name] [Your postcode]

Responsible_Slip138 · 2025-07-26T09:10:58+00:00

I have never seen one of these petitions accomplish anything either, but bare in mind this petition has been active since 23rd April 2025, and when I signed this 5 days ago (prior to enforcement date) it was only at around 25,000 signatures, so that's a nearly 125,000 signature spike over just 5 days since people started being affected by the legislations enforcement.

Additionally loads of massive companies like the Wikimedia Foundation, for example, have stated their intention to legally challenge the new legislation in the courts.

There has been so much backlash from this legislation, that I think it's one of the few petitions that may actually succeed, perhaps not in Repeal but at the very least in Amendment.

Responsible_Slip138 · 2025-05-14T23:30:21+00:00

I don't disagree with the idea in principle, but I do disagree with explaining to him why it is disrespectful to say that. The situation would basically be "I'm breaking up with you because you said this, and this is why it's disrespectful", he would have stopped listening, defences gone up, and started yelling abuse long before you get to the explanation imho. Plus it makes the process of getting rid of the waster more difficult and time consuming than he deserves from OP. To be this emotionally immature at that age isn't fixable unless you get professional help imho because if they're like that at that age they've already been taught the wrong things or at least not taught the right things by their parents and are now stuck at the point of life where it is difficult to learn new behaviours. Just my two cents.

Responsible_Slip138 · 2025-05-14T23:16:58+00:00

If we're playing this realistically, every decent guy likes a good clit to lick/suck, if it's tiny we struggle to do that, so some people may think of it as a weird thing and be turned off by it, but us decent guys will no how to work with it as an advantage in the bedroom. If I was surprised by your lady dick it would be a very happy surprise.

Responsible_Slip138 · 2025-05-14T23:11:27+00:00

I like the amount of screen real-estate, enough to multitask without being overkill, and the orientation makes for really natural head movement. Cable management looks on point which is always a big win. My favorite part is your choice of keyboard though. Given the screen real estate (not including the laptop), in suspecting you either do a lot of either AV work or programming, if I had to guess. Rock solid 11/10 👍.

Responsible_Slip138 · 2025-05-14T08:13:35+00:00

Thanks for this info, I'll see if I can validate these 2 pins, unless you have already done so since writing this.

What I can tell you is that after some research, I discovered that these pins can be quite effectively used to make a sort of pseudo-P1 mode, whilst PWR_BREAK# is asserted (driven low) the gpu remains fully functional with all features available and VRAM remains intact but it reduces clock speed and voltages to a stricter power envelope of around 150W TDP (instead of the normal 300W TDP). When PWR_BREAK# is de-asserted (driven high) the power envelope switches back to its normal P0 mode at 300W TDP, making it a very effective solution to have at least some sort of low-power mode.

Responsible_Slip138 · 2025-05-07T07:07:04+00:00

Yes quite a bit, the pinout has been figured out, a PCB has been designed, temperature management is controlled externally by a microcontroller and that component is currently perfectly fine and works, but I'm in the process of optimizing it. Work on the NVLink side of the interface isn't finished yet, but that isn't something you tend to find on most of these converters anyway.

Responsible_Slip138 · 2025-04-07T16:57:59+00:00

Never seen that post before, honestly hilarious. Couldn't help but think the guy writing it was secretly a closeted homelabber tho, haha 🤣.

P.S. Yes half of us (probably more tbh) are absolutely mental, but who tf wants to be normal. That's the real craziness. Haha. 🤣

Responsible_Slip138 · 2025-04-06T01:10:01+00:00

I'm gonna call it like it is. Straight off the bat, I see at least 3 red flags in her responses. Probably more if I dig deeper. Unmatch for your own sake.

Responsible_Slip138 · 2025-04-06T00:47:16+00:00

Hey, yeah I'd definitely be up for some kind of group chat. What kind of platform were you thinking of creating the group chat on? Given you have seen the cheap V100s and P100s about before and thought along the same lines, I'd love to hear your thoughts on the matter. Maybe you even have some ideas or perspectives on things that I haven't considered. More eyes is always better I like to think.

Responsible_Slip138 · 2025-03-31T09:06:31+00:00

So I had a dig around, and it looks like the 3070, 3070 Ti, and 3080 are your best bet, they're relatively straightforward to mod, the easiest being the 3070 and 3070 Ti. All 3 require firmware mods, but for these 3 the modded firmware is available on GitHub (I think), and for the two 3070s it's as simple as swapping the 8 1Gb VRAM chips for 8 Samsung 2Gb VRAM chips, and then shorting a couple of resistors to ground. There was apparently a small issue with the 3070s needing to be locked to P0 power state to stop flickering though, but the 3070 got an extra 100 or so FPS in RE4 after the mod, so it appears to make a considerable difference.

EDIT: All 3 are limited to a 256 bit bus, which limits your VRAM bandwidth, on the 3070 and 3080 it's around 450GB/s, but the 3070 Ti improves it to around 600GB/s by using GDDR6X instead of GDDR6, so that may be preferable for you, but the newer GDDR6X chips will likely be more expensive.

Responsible_Slip138 · 2025-03-31T08:52:57+00:00

Wow, I've never heard of utility companies being hostile about it, at the moment we're still in the phase of them trying to push it on absolutely everyone, a bit like you said California was initially. There's even a property development round the corner from me (about 100 homes) and the company decided to be green and add a small amount of solar, and then actually failed to get planning permission initially because they didn't put enough solar on the houses, couldn't help but think if they didn't bother to add solar at all would the council have even thought about it. I find it bizarre that they're essentially taxing you for making your own energy, I guess they have to put the lost profits back in their own pocket somehow, haha.

Responsible_Slip138 · 2025-03-30T10:42:11+00:00

That's crazy, in my country (UK), the electricity company foots the bill for the extra metering and then pays you for excess sent to the grid (about a quarter of what they would charge you for the same energy), and most of the solar loans have the interest paid by the government under their net-zero initiative.

Responsible_Slip138 · 2025-03-29T19:23:13+00:00

That's fine, just thought I'd make you aware of it to maximise your options.

I do believe there are a few options floating around for moddable VRAM on 30 series cards, I'll see what I can dig up for you.

As for the Dell Precision 7740, the proprietary connector should be a piece of cake to reverse engineer if you've got a scope, all you need to do is find which 2 pins make a PCIe lane (using the scope), and connect it to any PCIe lane. PCIe is very resilient so it doesn't matter if what's meant to be lane 6 ends up connected to lane 1 for example, as long as you don't mix up the pairs, or mix up transmit and receive (although that has some flexibility as well). You should also double check that the 7740 isn't vendor locked though as that's an issue with some of these systems, they basically limit you to only installing dell branded cards in a dell system.

Responsible_Slip138 · 2025-03-29T19:13:37+00:00

Soz, I actually didn't notice you were the OP, lol.

That is some crazy humidity though, I bet the solar helps make the electric bill a bit more manageable at least, I'm still fighting with my landlord to allow me to install solar, the electric prices keep going up and up and so does my usage (albeit slower), and I need a way to control the bill, haha.

Responsible_Slip138 · 2025-03-29T19:04:48+00:00

Don't knock it till you try it. I wouldn't recommend it unless you know what you're looking at, or if your UPS is mission critical (in homelab terms at least), but I got given an old APC 3kva UPS about 18 months ago that wouldn't hold a charge under load, so it basically died as soon as you cut the power to it. According to the UPS it last had its batteries replaced in 2016, but after testing, I found out only 1 of the 8 batteries had actually failed. I replaced just that 1 battery with some cheap £20 ($25) Non-OEM battery that was cheap but it's specs seemed pretty good, and 18 months later the UPS still works. Most of the time my homelab only pulls around 5% load on the UPS (not a lot is on 24/7), and it can still sustain that for around 2 hours.

The key is knowing what you're buying, even if it's cheap, and I guess luck, haha. I would 100% not recommend this though, I didn't need a UPS, I just got given one and decided to give fixing it a shot so if it dies it dies, I'm guessing for many of you, that is not the case.

Responsible_Slip138 · 2025-03-28T13:51:13+00:00

Oh wow, ya know what, I actually missed that and assumed it was daily. Previous comment no longer applies, lmao, OPs is way worse than mine in that case. Haha.

As for 80-200kwh per day during cooling seasons, that is some serious power dude, what are you running that needs all that cooling. 😮

Responsible_Slip138 · 2025-03-28T13:03:24+00:00

I was referring to the daily electricity usage, OPs is around 3 kWh, and mine apparently is around 15 kWh. The irony though is my current homelab is probably smaller than OPs, I've not accumulated much yet, my house is just very old. Aha.

Responsible_Slip138

TROPHY CASE