PCIe 8.0 announced by the PCI-Sig will double throughput again

https://www.servethehome.com/pcie-8-0-announced-by-the-pci-sig-will-double-throughput-again/

68•rbanffy•3d ago

Comments

SlightlyLeftPad•3d ago

Any EEs that can comment on at what point do we just flip the architecture over so the GPU pcb is the motherboard and the cpu/memory lives on a PCIe slot? It seems like that would also have some power delivery advantages.

vincheezel•3d ago

Good to see I’m not the only person that’s been thinking about this. Wedging gargantuan GPUs onto boards and into cases, sometimes needing support struts even, and pumping hundreds of watts through a power cable makes little sense to me. The CPU, RAM, these should be modules or cards on the GPU. Imagine that! CPU cards might be back..

ksec•3d ago

It is not like CPU aren't getting higher wattage as well. Both AMD and Intel have roadmap for 800W CPU.

At 50-100W for IO, this only leaves 11W per Core on a 64 Core CPU.

linotype•3h ago

800 watt CPU with a 600 watt GPU, I mean at a certain point people are going to need different wiring for outlets right?

jchw•2h ago

At least with U.S. wiring we have 15 amps at 120 volts. For continuous power draw I know you'd want an 80% margin of safety, so let's say you have 1440 Watts of AC power you can safely draw continuously. Power supplies built on MOSFETs seem to peak at around 90% efficiency, but you could consider something like the Corsair AX1600i using gallium nitride transistors, which supposedly can handle up to 1600 watts at 94% efficiency.

Apparently we still have room, as long as you don't run anything else on the same circuit. :)

cosmic_cheese•2h ago

Where things get hairy are old houses with wiring that’s somewhere between shaky and a housefire waiting to happen, which are numerous.

kube-system•2h ago

Yeah, but it ain't nothing that microwaves, space heaters, and hair dryers haven't already given a run for their money.

jchw•49m ago

Hair dryers and microwaves only run for a few minutes, so even if you do have too much resistance this probably won't immediately reveal a problem. A space heater might, but most space heaters I've come across actually seem to draw not much over 1,000 watts.

And even then, even if you do run something 24/7 at max wattage, it's definitely not guaranteed to start a fire even if the wiring is bad. Like, as long as it's not egregiously bad, I'd expect that there's enough margin to cover up less severe issues in most cases. I'm guessing the most danger would come when it's particularly hot outside (especially since then you'll probably have a lot of heat exchangers running.)

jchw•45m ago

As an old house owner, I can attest to that for sure. In fairness though, I suspect most of the atrocities occur in wall and work boxes, as long as your house is new enough to at least have NM sheathed wiring instead of ancient weird stuff like knob and tube. That's still bad but it's a solvable problem.

I've definitely seen my share of scary things. I have a lighting circuit that is incomprehensibly wired and seems to kill LED bulbs randomly during a power outage; I have zero clue what is going on with that one. Also, often times opening up wall boxes I will see backstabs that were not properly inserted or wire nuts that are just covering hand-twisted wires and not actually threaded at all (and not even the right size in some cases...) Needless to say, I should really get an electrician in here, but at least with a thermal camera you can look for signs of serious problems.

atonse•2h ago

You can always have an electrician install a larger breaker for a particular circuit. I did that with my "server" area in my study, which was overkill cuz I barely pull 100w on it. But it cost nearly zero extra since he was doing a bunch of other things around the house anyway.

davrosthedalek•1h ago

Larger breaker and thicker wires!

atonse•1h ago

I thought you only needed thicker wires for higher amps? Should go without saying, but I am not a certified electrician :-)

I only have a PhD from YouTube (Electroboom)

jchw•1h ago

The voltage is always going to be the same because the voltage is determined by the transformers leading to your service panel. The breakers break when you hit a certain amperage for a certain amount of time, so by installing a bigger breaker, you allow more amperage.

If you actually had an electrician do it, I doubt they would've installed a breaker if they thought the wiring wasn't sufficient. Truth is that you can indeed get away with a 20A circuit on 14 AWG wire if the run is short enough, though 12 AWG is recommended. The reason for this is voltage drop; the thinner gauge wire has more resistance, which causes more heat and voltage drop across the wire over the length of it, which can cause a fire if it gets sufficiently hot. I'm not sure how much risk you would put yourself in if you were out-of-spec a bit, but I wouldn't chance it personally.

chronogram•2h ago

That's still not much for wiring in most countries. A small IKEA consumer oven is only 230V16A=3860W. Those GPUs and CPUs only consume that much at max usage anyway. And those CPUs are uninteresting for consumers, you only need a few Watts for a single good core, like a Mac Mini has.

dv_dt•2h ago

So Europe ends up with an incidental/accidental advantage in the AI race?

buckle8017•2h ago

In residential power delivery? yes

In power cost? no

I'm literally any other way? also no

kube-system•2h ago

Consumers with desktop computers are not winning any AI race anywhere.

atonse•2h ago

All American households get mains power at 240v (I'm missing some nuance here about poles and phases, so the electrical people can correct my terminology).

It's often used for things like ACs, Clothes Dryers, Stoves, EV Chargers.

So it's pretty simple for a certified electrician to just make a 240v outlet if needed. It's just not the default that comes out of a wall.

kube-system•1h ago

To get technical -- US homes get two phases of 120v that are 180 degrees out of phase with the neutral. Using either phase and the neutral gives you 120v. Using the two out of phase 120v phases together gives you a difference of 240v.

https://appliantology.org/uploads/monthly_2016_06/large.5758...

ender341341•1h ago

Even more technical, we don't have two phases, we have 1-phase that's split in half. I hate it cause it makes it confusing.

Two phase power is not the same as split phase (There's basically only weird older installations of 2 phase in use anymore).

kube-system•1h ago

Yeah that's right. The grid is three phases (as it is basically everywhere in the world), and the transformer at the pole splits one of those in half. Although, what are technically half-phases are usually just called "phases" when they're inside of a home.

voxadam•1h ago

Relevant video from Technology Connections:

"The US electrical system is not 120V" https://youtu.be/jMmUoZh3Hq4

atonse•1h ago

That's such a great video, like most of his stuff.

dv_dt•1h ago

Well yes its possible but often $500-1000 to run a new 240v outlet, and that's to a garage for an ev charger. If you want an outlet in the house I dont know how much wall people want to tear up and extra time and cost.

atonse•1h ago

Sure yeah, I was just clarifying that if the issue is 240v, etc, US houses have the feed coming in. Infrastructure-wise it's not an issue at all.

ender341341•1h ago

> So it's pretty simple for a certified electrician to just make a 240v outlet if needed. It's just not the default that comes out of a wall.

It'd be all new wire run (120 is split at the panel, we aren't running 240v all over the house) and currently electricians are at a premium so it'd likely end up costing a thousand+ to run that if you're using an electrician, more if there's not clear access from an attic/basement/crawlspace.

Though I think it's unlikely we'll see an actual need for it at home, I imaging a 800w cpu is going to be for server class CPUs and rare-ish to see in home environments.

vel0city•10m ago

I don't think many people would want some 2kW+ system sitting on their desk at home anyways. That's quite a space heater to sit next to.

carlhjerpe•1m ago

In the Nordics we're on 10A for standard wall outlets so we're stuck on 2300W without rewiring (or verifying wiring) to 2.5mm2.

We rarely use 16A but it exists. All buildings are connected to three phases so we can get the real juice when needed (apartments are often single phase).

I'm confident personal computers won't reach 2300W anytime soon though

orra•2h ago

Laughs in 230V (sorry).

tracker1•2h ago

There already are different outlets for these higher power draw beasts in data centers. The amount of energy used in a 4u "AI" box is what an entire rack used to draw. Data centers themselves are having to rework/rewire areas in order to support these higher power systems.

t0mas88•2h ago

A simple kitchen top water cooker is 2000W, so a 1500W PC sounds like no big deal.

kube-system•2h ago

Kettles in the US are usually 1500W, as the smallest branch circuits in US homes support 15A at 120V and the general rule for continuous loads is to be 80% of the maximum.

linotype•1h ago

True but kettles rarely run for very long.

kube-system•1h ago

But computers do, which was why I included that context. You don't really want to build consumer PC >1500W in the US or you'd need to start changing the plug to patterns that require larger branch circuits.

CyberDildonics•28m ago

Kettles and microwaves are usually 1100 watts and lower, but space heaters and car chargers can be 1500 watts and run for long periods of time.

triknomeister•1h ago

And cooling. Look here: https://www.fz-juelich.de/en/news/archive/press-release/2025...

Especially a special PDU: https://www.fz-juelich.de/en/newsroom-jupiter/images-isc-202...

And cooling: https://www.fz-juelich.de/en/newsroom-jupiter/images-isc-202...

avgeek23•3d ago

And the memory should be a onboard module on the cpu card intel/amd should replicate what apple did with a unified same ringbus sort of memory modules. Lower latency,higher throughput.

Would push performance further. Although companies like intel would bleed the consumer dry with, a certain i5-whatever cpu with onboard memory of 16 gigs could be insanely priced compared to what you'd pay for addon memory.

0x457•26m ago

That would pretty much make both intel and amd to start market segmentation by CPU Core + Memory combination. I absolutely do not want that.

sitkack•2h ago

https://en.wikipedia.org/wiki/Compute_Express_Link

derefr•1h ago

But all of the most-ridiculous hyperscale deployments, where bandwidth + latency most matter, have multiple GPUs per CPU, with the CPU responsible for splitting/packing/scheduling models and inference workloads across its own direct-attached GPUs, providing the network the abstraction of a single GPU with more (NUMA) VRAM than is possible for any single physical GPU to have.

How do you do that, if each GPU expects to be its own backplane? One CPU daughterboard per GPU, and then the CPU daughterboards get SLIed together into one big CPU using NVLink? :P

verall•3h ago

If you look at a any of the nvidia DGX boards it's already pretty close.

PCIe is a standard/commodity so that multiple vendors can compete and customers can save money. But at 8.0 speeds I'm not sure how many vendors will really be supplying, there's already only a few doing serdes this fast...

MurkyLabs•2h ago

Yes I agree, let's bring back the SECC style CPU's from the Pentium Era, I've still got my Pentium II (with MMX technology)

Razengan•2h ago

Isn't that what has kinda sorta basically happened with Apple Silicon?

MBCook•30m ago

GPU + CPU on the same die, RAM on the same package.

A total computer all-in-one. Just no interface to the world without the motherboard.

Dylan16807•2h ago

And limit yourself to only one GPU?

Also CPUs are able to make use of more space for memory, both horizontally and vertically.

I don't really see the power delivery advantages, either way you're running a bunch of EPS12V or similar cables around.

burnt-resistor•2h ago

Figure out how much RAM, L1-3|4 cache, integer, vector, graphics, and AI horsepower is needed for a use-case ahead-of-time and cram them all into one huge socket with intensive power rails and cooling. The internal RAM bus doesn't have to be DDRn/X either. An integrated northbridge would deliver PCIe, etc.

kvemkon•1h ago

> at what point do we just flip the architecture over so the GPU pcb is the motherboard and the cpu/memory

Actually the RapsberryPi (appeared 2012) was based on a SoC with a big and powerful GPU and small weak supporting CPU. The board booted the GPU first.

LeoPanthera•1h ago

Bring back the S100 bus and put literally everything on a card. Your motherboard is just a dumb bus backplane.

MBCook•32m ago

We were moving that way, sorta, with Slot 1 and Slot A.

Then that became unnecessary when L2 cache went on-die.

leoapagano•22m ago

One possible advantage of this approach that no one here has mentioned yet is that it would allow us to put RAM on the CPU die (allowing for us to take advantage of the greater memory bandwidth) while also allowing for upgradable RAM.

zkms•2h ago

My reaction to PCIe gen 8 is essentially "Huh? No, retro data buses are like ISA, PCI, and AGP, right? PCIe Gen 3 and SATA are still pretty new...".

I wonder what modulation order / RF bandwidth they'll be using on the PHY for Gen8. I think Gen7 used 32GHz, which is ridiculously high.

eqvinox•2h ago

I'd highly advise against using GHz here (without further context, at least), a 32Gbaud / 32Gsym/s NRZ signal toggling at full rate is only a 16GHz square wave.

baud seems out of fashion, sym/s is pretty clear & unambiguous.

(And if you're talking channel bandwidth, that needs clarification)

kvemkon•2h ago

> > I think Gen7 used 32GHz, which is ridiculously high.

> 16GHz square wave

Is it for PCIe 5.0? PCIe 6.0 should operate on the same frequency and doubling the bandwidth by using PAM4. If PCIe 7.0 doubled the bandwidth and is still PAM4, what is the underlying frequency?

eqvinox•1h ago

PCIe 7 = 128 GT/s = 64 Gbaud × PAM-4 = 32 "GHz" (if you alternate extremes on each symbol)

for gen6, halve all numbers

Dylan16807•1h ago

Is it me or are they using the term GigaTransfers wrong? They're counting a single PAM4 pulse as two "transfers".

eqvinox•1h ago

They kinda are and kinda aren't, they're just using their own definition…

(I'm accepting it because "Transfers"/"T" as unit is quite rare outside of PCIe)

zamalek•15m ago

GT/s is also gaining ground for system RAM in order to clear up the ambiguity that DDR causes for end-consumers.

guerrilla•1h ago

> baud seems out of fashion, sym/s is pretty clear & unambiguous.

Huh? Baud is sym/s.

eqvinox•1h ago

Yes, that was the implication, but I've been getting the impression that using baud is kinda unpopular compared to using sym/s.

throwway120385•4m ago

A lot of people think that baud rate represents bits per second, which it only does in systems where the symbol set is binary. People got it from RS232.

Dylan16807•1h ago

> PCIe Gen 3 and SATA are still pretty new...

That's an interesting thought to look at. PCIe 3 was a while ago, but SATA was nearly a decade before that.

> I wonder what modulation order / RF bandwidth they'll be using on the PHY for Gen8. I think Gen7 used 32GHz, which is ridiculously high.

Wikipedia says it's planned to be PAM4 just like 6 and 7.

Gen 5 and 6 were 32 gigabaud. If 8 is PAM4 it'll be 128 gigabaud...

weinzierl•11m ago

Don't forget VESA Local Bus.

bhouston•2h ago

I love the PCIe standard is 3 generations ahead of what is actually released. Gen5 is the live version, but the team behind it is so well organized that they have a roadmap of 3 additional versions now. Love it.

ThatMedicIsASpy•2h ago

Gen6 is in use look at Nvidia ConnectX-8

drewg123•2h ago

What hosts support Gen6? AFAIK, Gen5 is the most recent standard that's actually deployed. Eg, what can you plug a CX8 into that will link up at Gen6?

triknomeister•1h ago

Custom Nvidia network cards I guess.

my123•1h ago

Blackwell DC (B200/B300)

tails4e•2h ago

It takes a long time to get form standard to silicon, so I bet there are design teams working on pcie7 right now, which won't see products for 2 or more years

Seattle3503•1h ago

Is there an advantage of getting so far ahead of implementations? It seems like it would be more difficult to incorporate lessons.

kvemkon•1h ago

When AMD introduces a new Desktop CPU series IIRC they claim the next generation design is (almost) finished (including layout?) and they start with the next-next-gen design. And I'm also asking the same question. But more than a half a year before the CPU becomes available to the public it is already being tested by partners (mainboard manufacturers and ?).

Phelinofist•51m ago

So we can skip 6 and 7 and go directly to 8, right?

ThatMedicIsASpy•2h ago

I'll take it if my consumer mb chipset supports giving me 48 PCIe7 lanes if future desktops still would only come with 24 gen 8 lanes

richwater•2h ago

Meanwhile paying a premium for a Gen5 motherboard may net you somewhere in the realm of 4% improvements in gaming if you're lucky.

Obviously PCI is not just about gaming but...

simoncion•1h ago

From what I've seen, the faster PCI-E bus is important when you need to shuffle things in and out of VRAM. In a video game, the faster bus reduces the duration of stutters caused by pushing more data into the graphics card.

If you're using a new video card with only 8GB of onboard RAM and are turning on all the heavily-advertised bells and whistles on new games, you're going to be running out of VRAM very, very frequently. The faster bus isn't really important for higher frame rate, it makes the worst-case situations less bad.

I get the impression that many reviewers aren't equipped to do the sort of review that asks questions like "What's the intensity and frequency of the stuttering in the game?" because that's a bit harder than just looking at average, peak, and 90% frame rates. The question "How often do textures load at reduced resolution, or not at all?" probably requires a human in the loop to look at the rendered output to notice those sorts of errors... which is time consuming, attention-demanding work.

Dylan16807•1h ago

There's a good amount of reviewers showing 1% lows and 0.1% lows, which should capture stuttering pretty well.

I don't know how many games are even capable of using lower resolutions to avoid stutter. I'd be interested in an analysis.

jeffbee•1h ago

By an overwhelming margin, most computers are not in gamers' basements.

LeoPanthera•1h ago

I thought we were only just up to 5? Did we skip 6 and 7?

pkaye•32m ago

Some of the newer ones maybe more for data centers.

robotnikman•36m ago

I know very little about electronics design, so I always find it amazing that they keep managing to double PCIe throughput over and over. Its also probably the longest lived expansion bus at the moment.

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Comments

PYX: The next step in Python packaging

Nginx introduces native support for ACME protocol

NIST Finalizes 'Lightweight Cryptography' Standard to Protect Small Devices

OCaml as my primary language

VC-backed company just killed my EU trademark for a small OSS project

FFmpeg 8.0 adds Whisper support

Illinois bans use of artificial intelligence for mental health therapy

PCIe 8.0 announced by the PCI-Sig will double throughput again

Launch HN: Golpo (YC S25) – AI-generated explainer videos

Cross-Site Request Forgery

So what's the difference between plotted and printed artwork?

Rerank-2.5 and rerank-2.5-lite: instruction-following rerankers

Pebble Time 2 Design Reveal [video]

Coalton Playground: Type-Safe Lisp in the Browser

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Fighting with YouTube to show a preview image

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Electrically controlled heat transport in graphite films

Claude says “You're absolutely right!” about everything

We caught companies making it harder to delete your personal data online

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