[HN Gopher] Say No to the Paywall of PCI-E Bifurcation
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Say No to the Paywall of PCI-E Bifurcation
Author : aleph1
Score : 57 points
Date : 2024-09-19 18:45 UTC (1 days ago)
(HTM) web link (www.grayxu.cn)
(TXT) w3m dump (www.grayxu.cn)
| devwastaken wrote:
| 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.
| crote wrote:
| I believe this has essentially been solved by the AM5 platform.
| The Ryzen 7000 IO die has a x16 slot which can usually be
| configured as 4x4, and has a tiny igpu which should be plenty
| for occasional server use.
|
| The budget Ryzen 8000 CPUs are indeed quite limited, which is a
| shame if you wanted to go for an 8000G APU to use its powerful
| iGPU for transcoding.
| bdhess wrote:
| 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.
| hakfoo wrote:
| I'm sort of amazed these days that we still have commercial
| BIOSes (well, UEFIs)
|
| They're not a selling point, even for the enthusiasts who buy
| individual motherboards.
|
| You'd think that that by now, the chipset vendors would provide
| a reference Coreboot image for each new platform, (which, since
| it would be more or less for debugging purposes, would have MAX
| OPTIONS) and then the motherboard manufacturers would do the
| bare minimum to cut off any features not relevant to their
| boards or swap in modules for whichever small technical
| deltas-- different audio chipsets or clock generators-- they
| actually make underneath the garish silkscreen and RGB strips.
| winocm wrote:
| 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.
| hkgjjgjfjfjfjf wrote:
| Tianocore
| jeroenhd wrote:
| Motherboard manufacturers would much rather pay AMI or Insyde
| a non-insignificant amount of money to make all BIOS
| development go away.
|
| They could hire people to do the work for them, but that'd
| require finding and vetting people with the necessary skills
| without the knowledge of how to do so. As long as BIOS
| manufacturers can sell their services for cheaper than
| setting up an extra firmware department, they'll do good
| business.
| crote wrote:
| The problem with this argument is that 1) bifurcation often
| still isn't available on enthusiast-level motherboards which
| are _filled_ with features catered to hobbyists, and 2) all
| motherboards are using variations on the same handful of BIOS
| firmware images.
|
| Same-slot bifurcation controlled by the BIOS requires basically
| zero additional testing. If it works on one board, it's pretty
| much guaranteed to work on another. After all, it's nothing
| more than a feature flag toggle.
|
| They have already invested the money into developing the
| software feature, because some boards _do_ have bifurcation. So
| why isn 't it available on on all enthusiast-level boards? Or
| even worse, why are they spending extra time and energy into
| disabling it on cheap motherboards?
| zamadatix wrote:
| If motherboard vendors are doing this out of only leaving
| settings for the things they've properly QA'd and can guarantee
| to work 100% of the time then half of the settings of most
| boards are in need of disabling as well.
| reginald78 wrote:
| If the board has PCI-E slots, it should support their features.
| If customers never used them they would have been dropped for
| cost reasons and no one would care. And indeed there are plenty
| of mini PCs and laptops where that is the case. Presumably
| people not buying those have their reasons.
| nubinetwork wrote:
| 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...
| nisegami wrote:
| Isn't that exactly why bifurcation is desirable?
| freeone3000 wrote:
| 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.
| myself248 wrote:
| 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.
| atmanactive wrote:
| The problem is the physical slot waste. If you have x16
| slot and you put an x16 GPU card into it (like majority of
| people do), then, there is no waste whatsoever. But, if you
| put an x8 GPU or some other x4 or x1 card, then, there is a
| lot of PCIe lanes wasted, simply because you can't
| physically access them anymore. When your MBD can
| bifurcate, for example x8+x8, then, a PS10 PCIe dongle can
| split that one x16 PCIe slot into two x8 PCIe slots.
| zamadatix wrote:
| I miss the ~X99 era of HEDT where the price to go from the
| consumer Z77 class stuff in the article to the "workstation"
| class was very minimal. The low end "Xeon" processors were had
| all with the consumer Haswell models had, including single core
| performance and relative price equivalence, but you got 4 memory
| channels, the ability to drive massive amounts of memory, ECC
| support, and 40 PCIe lanes from the CPU.
|
| Nowadays if you want to buy HEDT you either get a very fast
| version of the consumer part which is still extremely lane
| limited (limiting the usefulness of features like bifurcation),
| still has 2 memory channels, has the same memory capacity limits
| as that 10 year old X99 platform, and may or may not have usable
| ECC support (depending on the particular board and/or platform
| chipset options for that year) OR you can spend way more to get a
| CPU which is worse performing unless you need 32+ cores (and the
| even higher cost associated with that) but at least the platform
| has all that original HEDT capability.
|
| The 1st generation of Threadripper was a bit like that too,
| albeit AMDs CPUs weren't the top performers of the day when that
| came out and they've since gone up accordingly.
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