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#pcie#gpu#signalintegrity

How many PCIe Extensions is TOO MANY??

Linus Tech Tips

16M subscribers • 10 videos on Hallway

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  • Recommended by 1 person: 1 on Hacker News.
  • Presented by Linus Sebastian

Beginner. No background in the topic needed.

2.7M views9 years ago1 recommendation

HardwareElectronicsCPUs and computer architecture

Linus Sebastian tests how many PCIe riser cables can be chained together before signal degradation causes GPU performance loss or failure.

Thanks to LG for sponsoring this video! Check out their Share the Art #LG gram campaign: lggramevent.com youtu.be/6oKU9APBrwI Learn more about LG gram laptops lg.com/us/laptops/ Can PCIe extensions cause a loss in GPU performance? We investigate!! Tunnelbear sponsor link: Visit tunnelbear.com/LTT and start your 7-day free trial today! Buy PCIe extensions Amazon: geni.us/Ej85Tkv Newegg: geni.us/Xu5qQN Discuss on the forum: linustechtips.com/main/topic/829258-how-many-pcie-extensions… Our Affiliates, Referral Programs, and Sponsors: linustechtips.com/main/topic/75969-linus-tech-tips-affiliate… Linus Tech Tips merchandise at designbyhumans.com/shop/LinusTechTips/ Linus Tech Tips posters at crowdmade.com/linustechtips Our production gear: geni.us/cvOS Twitter - twitter.com/linustech Facebook - facebook.com/LinusTech Instagram - instagram.com/linustech Twitch - twitch.tv/linustech Intro Screen Music Credit: Title: Laszlo - Supernova Video Link: youtube.com/watch?v=PKfxmFU3lWY iTunes Download Link: itunes.apple.com/us/album/supernova/id936805712 Artist Link: soundcloud.com/laszlomusic Outro Screen Music Credit: Approaching Nirvana - Sugar High youtube.com/approachingnirvana Sound effects provided by freesfx.co.uk/sfx/

Why it's here

1 person recommends this, 1 disputes it

What people say. Recommended as a practical demonstration of PCIe signal integrity limits and the effects of chaining riser cables.

Uehrekaon Hacker News • Recommends

On “Raspberry Pi PCIe Devices”

I love a good “PCI Challenge”, where someone tries to see how much functionality they can wring out of PCI devices in a weird situation. Linus Tech Tips has a bunch of good ones: - How crazy of a device can you use with a server motherboard’s PCI hot-swap BIOS feature: link - How many PCI extenders can you use with a high end graphics card: link to this video
View on Hacker News

teromon Hacker News • Disputes

On “We Need New Motherboards Before GPUs Collapse Under Their Own Gravity”

I wonder if that benchmark actually loaded the PCIe bus to any significant degree after the initial benchmark startup, or just updated a couple small parameters on a single scene and thus mainly just tested the local computation on the GPU? You'd want to somehow monitor the PCIe bus error rate - with a marginal signal and lots of errors -> retries, something that loads the bus harder (loading new textures etc) could suffer way more. They do briefly show a different PCIe riser made out of generic ribbon cable 1, 3:27, and say that one failed after chaining only two ~200mm lengths. The quality of the riser cable certainly matters. 1 link to this video
View on Hacker News

velox_ioon Hacker News • Mentions

On “Cray and Microsoft Bring Supercomputing to Azure”

It's a shame you can't get a cable to link computers via PCIe (supports cables over 3m0). Multiple x16 connections that would lead to some decent bandwidth while being low-latency, without the network overhead or shelling out for high-end switches. You can skip halfway. 0 link to this video
View on Hacker News

jacooperon Hacker News • Mentions

On “We Need New Motherboards Before GPUs Collapse Under Their Own Gravity”

Here is an LTT video about how many PCI-E extensions one can daisychain without problems. The limit is around 3 meters. link to this video
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luminiferouson Hacker News • Mentions

On “We Need New Motherboards Before GPUs Collapse Under Their Own Gravity”

LTT has a video where they tried to see how many PCIe riser cables they could string together before it stopped working.1 They got to several meters. Maybe you could argue that it's worse inside a PC case since there's more EMI, but it seems like your PCIe riser cable would have to be very out of spec before you'd notice anything. 1 link to this video
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ChoGGion Hacker News • Mentions

On “I rage-converted my RTX4090 into an eGPU”

Someone needs to get this man a speed square, also a longer riser cable 1. 1I don't care much for Linus Tech, but link to this video
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userbinatoron Hacker News • Mentions

On “Assembly Hall of Shame”

PCIe is more like a packet-switched network than a bus, which is incidentally why things like Thunderbolt (effectively external PCIe) and sillier demonstrations like link to this video work. ...and with things like link , you can get even higher latencies.
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