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Say No to the Paywall of PCI-E Bifurcation

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Re: Say No to the Paywall of PCI-E Bifurcation

#21

Post by 3np »

devwastaken wrote: post #2

Looking at asus's 4x nvme bifurcation card you cannot use an igpu enabled processor and maintain 4x4 with any CPU. I don't want to fill a slot with a dedicated GPU. For a NAS I don't need 4 in a pool, just 2 per slot works fine with HDD backups.

Hm, what do you mean? Unless it's an Intel thing:

For AM4: The ASUS card (at least the one I'm looking at) is PCIe4 4x4, while APUs only expose PCIe3. Should still work but over PCIe3 with X570. I've been running PCIe3 4x4 cards from other makers on that chipset and did not notice any issues.

For AM5 I don't see why not?

I have not tried but something like this might be what you are looking for? https://aliexpress.com/item/1005005311953959.html

There are bifurcation cards from other makers with other configurations also exposing two m2 slots, if you look around. E.g. https://www.10gtek.com/nvmessdadapterforu.2ssd

Re: Say No to the Paywall of PCI-E Bifurcation

#22

Post by 3np »

3np wrote: post #21
devwastaken wrote: post #2

Looking at asus's 4x nvme bifurcation card you cannot use an igpu enabled processor and maintain 4x4 with any CPU. I don't want to fill a slot with a dedicated GPU. For a NAS I don't need 4 in a pool, just 2 per slot works fine with HDD backups.

Hm, what do you mean? Unless it's an Intel thing: For AM4: The ASUS card (at least the one I'm looking at) is PCIe4 4x4, while APUs only expose PCIe3. Should still work but over PCIe3 with X570. I've been running PCIe3 4x4 cards from other makers on that chipset and did not notice any issues. For AM5 I don't see why not? I have not tried but something like this might be what you are looking for? https://aliexpress.co…

Follow-up: Just learned that so far AM5 is actually a regression compared to AM4[0]. The best they can give is exactly 16 usable lanes (4 of total 20 reserved for chipset). Zen4c models only give you 10. Between this and Pluton I'm quickly losing interest in AM5...

[0]: OK, total bandwidth is still obviously up because we have gained a PCIe generation but still I'd have expected available lane-count to not drop.

Re: Say No to the Paywall of PCI-E Bifurcation

#23

Post by vardump »

myself248 wrote: post #17
freeone3000 wrote: post #15

Earlier quoted context omitted.

Bifurcation lets you allocate the lanes in more configurations, but doesn’t actually give you more lanes or allow you to dynamically allocate a lane. Unless you’re connecting more devices than are planned for by the cpu and chipset, you’re not going to see an advantage.

Right, but if there's 8 lanes to spare, and I could use 4 for a 10GbE NIC and 4 for another NVMe drive, that's better than wasting all 8 on one of those functions and not being able to install the other at all.

Isn't 4 lanes for a 10 GbE NIC a complete overkill? Two lanes should be plenty. One would do, assuming your combined full duplex bandwidth doesn't exceed 16 Gbps (minus overhead).

For PCIe4, 4 lanes corresponds to 64 Gbps of bandwidth.

Re: Say No to the Paywall of PCI-E Bifurcation

#24

Post by devwastaken »

3np wrote: post #21
devwastaken wrote: post #2

Looking at asus's 4x nvme bifurcation card you cannot use an igpu enabled processor and maintain 4x4 with any CPU. I don't want to fill a slot with a dedicated GPU. For a NAS I don't need 4 in a pool, just 2 per slot works fine with HDD backups.

Hm, what do you mean? Unless it's an Intel thing: For AM4: The ASUS card (at least the one I'm looking at) is PCIe4 4x4, while APUs only expose PCIe3. Should still work but over PCIe3 with X570. I've been running PCIe3 4x4 cards from other makers on that chipset and did not notice any issues. For AM5 I don't see why not? I have not tried but something like this might be what you are looking for? https://aliexpress.co…

https://www.asus.com/us/support/faq/1037507/

Under CPU section.

Re: Say No to the Paywall of PCI-E Bifurcation

#25

Post by JackSlateur »

bdhess wrote: post #3

More config options means more to test and support, so more cost. The manufacturers who are buying lower end motherboards/chipsets at scale don’t need the feature. And virtually no consumer installs a PCI-E device, ever. So basically, it’s an argument to make all computers more expensive, in order to subsidize hobbyists.

GPU and NVMe are PCI-e devices, they are both widespreads, so I do not get your point

Re: Say No to the Paywall of PCI-E Bifurcation

#26

Post by wtallis »

3np wrote: post #22
3np wrote: post #21

Earlier quoted context omitted.

Hm, what do you mean? Unless it's an Intel thing: For AM4: The ASUS card (at least the one I'm looking at) is PCIe4 4x4, while APUs only expose PCIe3. Should still work but over PCIe3 with X570. I've been running PCIe3 4x4 cards from other makers on that chipset and did not notice any issues. For AM5 I don't see why not? I have not tried but something like this might be what you are looking for? https://aliexpress.co…

Follow-up: Just learned that so far AM5 is actually a regression compared to AM4[0]. The best they can give is exactly 16 usable lanes (4 of total 20 reserved for chipset). Zen4c models only give you 10. Between this and Pluton I'm quickly losing interest in AM5... [0]: OK, total bandwidth is still obviously up because we have gained a PCIe generation but still I'd have expected available lane-count to not drop.

AM5 is not a regression from AM4; it adds four more PCIe lanes. The laptop chips repackaged for the desktop socket don't have as many lanes, because laptop chips don't need that much IO.

Re: Say No to the Paywall of PCI-E Bifurcation

#27

Post by segmondy »

nubinetwork wrote: post #10

Most CPUs don't have the lanes for this anyways... after you install a video card and an NVME drive, you're lucky if you have 8 lanes to spare, let alone 16...

and yet, cheap $20 CPUs do have enough. My GPU rig runs dual e5-2680 $20 each. For $40 I have a total of 88 lanes. $160 dual server motherboard from Aliepxress. I currently have 6 GPUs. The motherboard supports PCIe bifurcation, so I don't really need this article. Just additional hardware to split the physical slots.

Re: Say No to the Paywall of PCI-E Bifurcation

#28

Post by 3np »

wtallis wrote: post #26
3np wrote: post #22

Earlier quoted context omitted.

Follow-up: Just learned that so far AM5 is actually a regression compared to AM4[0]. The best they can give is exactly 16 usable lanes (4 of total 20 reserved for chipset). Zen4c models only give you 10. Between this and Pluton I'm quickly losing interest in AM5... [0]: OK, total bandwidth is still obviously up because we have gained a PCIe generation but still I'd have expected available lane-count to not drop.

AM5 is not a regression from AM4; it adds four more PCIe lanes. The laptop chips repackaged for the desktop socket don't have as many lanes, because laptop chips don't need that much IO.

I'm talking about the AM5 desktop APU options (including announced PRO APUs), not the platform itself or laptop SKUs.

Re: Say No to the Paywall of PCI-E Bifurcation

#29

Post by winocm »

hkgjjgjfjfjfjf wrote: post #14
winocm wrote: post #5

Earlier quoted context omitted.

Honestly, if someone made a reference platform setup utility (and BDS initialization screen) for EFI systems with a familiar-ish UI and got it into upstream git, then I think a lot of the value add of commercial firmware would probably dissipate.

Tianocore

That’s the reference UI, I’m referring to something more akin to whatever ships on motherboards these days.
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