4 ms·

I was under the impression that AM5 would support PCIe 5.0 instead of 4.0. I’m becoming less excited about this next generation from AMD than I was a few months

by cebert 4y ago

I was under the impression that AM5 would support PCIe 5.0 instead of 4.0. I’m becoming less excited about this next generation from AMD than I was a few months ago.

wmf 4y ago
It will support PCIe 5.0 on the slots directly connected to the CPU, but probably only on X670E motherboards. Note that there will be very few 5.0 devices on the market and you won't be able to notice the performance difference.
- mahkeiro 4y ago
  Saying there are few devices yet on the market is not helpful. You don't buy a PC for the next 6 months. In a 1-2-3 years when your PC will be still ok it is very likely that more PCIe5.0 devices will be out, and probably not compatible with your MB.
  - NavinF 4y ago
    I upgrade every couple of years to the best hardware on the market, but even for me PCIe 5 is just “nice to have”. No GPUs support it yet and rumors suggest that RTX40 will also be PCIe 4.
- trashtester 4y ago
  My interpretation is that the chipsets wil have PCIEe 5 connections as follows: X670E: "Everywhere" according to the talk, which I interpret as: - 16 lanes of pcie 5 to the main pcie slots - 4 lanes of pcie 5 to the primary nvme slot (i would not be surprised if some boards will expose this as a pcie x 16 slot (with 4 lanes)) though. - 4 lanes of pcie 5 to the chipset (speculative) For the regular X670: - 16+4 pcie5 lanes to "GPU" and "nvme" slots, as for the X670, perhaps only 1 nvme slot, perhaps with an additional nvme x8 slot when running 8/8/4 instead of 16/0/4. - "only" nvme 4 to the chipset B570: - Only the "nvme" slot will have version 5 If I'm right, the Extreme card will offer twice the performance over the chipset, compared to AM4, which could allow it to fill some of the use cases currently covered by the non-pro threadrippers. If I'm wrong, and even the extreme X670E chipset will not be a good choice for those who depend on a lot of IO, compared to threadripper or Intel. Hopefully, I'm right, and in that case, I'm not sure if we need an intermediate step between the 7950x and lower end threadripper pro setups, at least not for connectivity and I/O. And those who actually need more compute than the 7950x will over will probably not care that much about the price premium of threadripper pro vs regular threadripper.
cududa 4y ago
What specific benefit are you expecting from PCIe 5
- cebert 4y ago
  I have an old Zen 1 desktop right that has served me well, but is becoming outdated. If I am going to upgrade to DDR5 and AM5, I’d prefer to be PCIe 5 compatible so that my upgrade investment is maximized.
- mjevans 4y ago
  I'd like room for addon cards with more NVME drives or existing RAID / JBOD bulk IO cards. I'd be fine with PCI-E 4 across: x16 (gpu) + x16 (gpu/accessory) + x4 (nvme) + x4 (nvme) + x4 (their slow IO chipset). PCI-E 5 is 2x the bandwidth, so maybe some higher end boards might offer more choices for splitting those lanes up at slower speeds that work well with older addin cards. A (1.25GB/sec) 10GBit Ethernet card is on the radar for the lifetime of these systems. A 4.0 x1 link is sufficient at ~ 1.97GB/sec. I'm worried too many boards will ship with two GPU slots (5.0? / 4.0 x8) and at most 2x NVME slots, and load _everything_ else on those x4 slots for the board chipsets, including accessory slots.
  - wtallis 4y ago
    The PCIe root ports in CPUs usually don't support dividing up x16 links into anything smaller than x4 links. Even for dedicated PCIe switch chips, bifurcation down to x2 or x1 links is usually only found on the smaller switches that don't have multiple x16 links to begin with—though PCIe gen4 and gen5 have made x2 link width support show up for some of the big PCIe switches. If you want to load up a bunch of low-speed devices (and 10Gbit/s is low-speed now), the chipset is the right place to do it. Consumer systems really are not going to be bottlenecked by lots of devices sharing one x4 uplink to the CPU.
    - mjevans 4y ago
      Sure, a chipset is the correct place to do that, but I'm worried about the bandwidth it can offer in this specific setup. The block diagrams show (for useful devices): CPU / APU: * RAM ??? * 5.0 x8 + 5.0 x8 GPU(s?) * 5.0 x4 NVMe * 4.0 x4 2x USB4 #1 * 4.0 x4 for PROM21 * DP / HDMI #1 * 2x USB 3.2 10Gbit * 3x USB 2.0 (why?) * SPI / GPIO HDAudio #1 #1 expected ASM4242 mux with 2x DP for APUs -- It'd be nice if these pins could export additional PCIe lanes for non-APU systems. That 4.0 x 4 set of lanes is expected to service up to... * 4.0 x4 (bridged daisy) * 4.0 x4 NVMe * 4x SATA 6Gbit/sec * USB 3.2 20Gbit * 4x USB 3.2 10Gbit * 4x USB 2.0 + * 4.0 x4 (daisy to cards) * 4.0 x4 NVMe * 3.0 x1 2.5Gbit Ether * 3.0 x1 + 2.0 USB WiFi * 2x SATA 6Gbit * USB 3.2 20Gbit * 4x USB 3.2 10Gbit * 4x USB 2.0 __ideally__ they'd have done something more like x4 PCIe 5.0 for the secondary NVMe drives and downstream system ports to share, along with an x2 PCIe 5.0 link utilized for the other existing ports on the two chips.
rasz 4y ago
it will, but only if you pay extra for fake "X670E" chipset while getting same X670 motherboard, but with unlocked pcie 5.0.
paulmd 4y ago
This has been clarified by the actual presentation: X670E gets PCIe 5 on all CPU links, X670 gets PCIe 5 on the first slot and storage, B650 gets PCIe 5 only on storage. Of course, the chipset itself has nothing to do with what connectivity is provided to the PEG slots since those run straight to the CPU - this is market segmentation in action, the CPU simply won't turn on those feature-bits if you don't pay for the premium chipset. Also, as noted, on AMD the chipset has nothing to do with anything anyway. It is just an IO expander, it doesn't boot the CPU or do anything like that, and it is entirely uninvolved, out of the loop entirely, when the CPU is talking to things that are attached to PEG direct lanes.

by cebert 4y ago

I was under the impression that AM5 would support PCIe 5.0 instead of 4.0. I’m becoming less excited about this next generation from AMD than I was a few months ago.

wmf 4y ago

It will support PCIe 5.0 on the slots directly connected to the CPU, but probably only on X670E motherboards. Note that there will be very few 5.0 devices on the market and you won't be able to notice the performance difference.

mahkeiro 4y ago
Saying there are few devices yet on the market is not helpful. You don't buy a PC for the next 6 months. In a 1-2-3 years when your PC will be still ok it is very likely that more PCIe5.0 devices will be out, and probably not compatible with your MB.
- NavinF 4y ago
  I upgrade every couple of years to the best hardware on the market, but even for me PCIe 5 is just “nice to have”. No GPUs support it yet and rumors suggest that RTX40 will also be PCIe 4.
trashtester 4y ago
My interpretation is that the chipsets wil have PCIEe 5 connections as follows: X670E: "Everywhere" according to the talk, which I interpret as: - 16 lanes of pcie 5 to the main pcie slots - 4 lanes of pcie 5 to the primary nvme slot (i would not be surprised if some boards will expose this as a pcie x 16 slot (with 4 lanes)) though. - 4 lanes of pcie 5 to the chipset (speculative) For the regular X670: - 16+4 pcie5 lanes to "GPU" and "nvme" slots, as for the X670, perhaps only 1 nvme slot, perhaps with an additional nvme x8 slot when running 8/8/4 instead of 16/0/4. - "only" nvme 4 to the chipset B570: - Only the "nvme" slot will have version 5 If I'm right, the Extreme card will offer twice the performance over the chipset, compared to AM4, which could allow it to fill some of the use cases currently covered by the non-pro threadrippers. If I'm wrong, and even the extreme X670E chipset will not be a good choice for those who depend on a lot of IO, compared to threadripper or Intel. Hopefully, I'm right, and in that case, I'm not sure if we need an intermediate step between the 7950x and lower end threadripper pro setups, at least not for connectivity and I/O. And those who actually need more compute than the 7950x will over will probably not care that much about the price premium of threadripper pro vs regular threadripper.

cududa 4y ago

What specific benefit are you expecting from PCIe 5

cebert 4y ago
I have an old Zen 1 desktop right that has served me well, but is becoming outdated. If I am going to upgrade to DDR5 and AM5, I’d prefer to be PCIe 5 compatible so that my upgrade investment is maximized.
mjevans 4y ago
I'd like room for addon cards with more NVME drives or existing RAID / JBOD bulk IO cards. I'd be fine with PCI-E 4 across: x16 (gpu) + x16 (gpu/accessory) + x4 (nvme) + x4 (nvme) + x4 (their slow IO chipset). PCI-E 5 is 2x the bandwidth, so maybe some higher end boards might offer more choices for splitting those lanes up at slower speeds that work well with older addin cards. A (1.25GB/sec) 10GBit Ethernet card is on the radar for the lifetime of these systems. A 4.0 x1 link is sufficient at ~ 1.97GB/sec. I'm worried too many boards will ship with two GPU slots (5.0? / 4.0 x8) and at most 2x NVME slots, and load _everything_ else on those x4 slots for the board chipsets, including accessory slots.
- wtallis 4y ago
  The PCIe root ports in CPUs usually don't support dividing up x16 links into anything smaller than x4 links. Even for dedicated PCIe switch chips, bifurcation down to x2 or x1 links is usually only found on the smaller switches that don't have multiple x16 links to begin with—though PCIe gen4 and gen5 have made x2 link width support show up for some of the big PCIe switches. If you want to load up a bunch of low-speed devices (and 10Gbit/s is low-speed now), the chipset is the right place to do it. Consumer systems really are not going to be bottlenecked by lots of devices sharing one x4 uplink to the CPU.
  - mjevans 4y ago
    Sure, a chipset is the correct place to do that, but I'm worried about the bandwidth it can offer in this specific setup. The block diagrams show (for useful devices): CPU / APU: * RAM ??? * 5.0 x8 + 5.0 x8 GPU(s?) * 5.0 x4 NVMe * 4.0 x4 2x USB4 #1 * 4.0 x4 for PROM21 * DP / HDMI #1 * 2x USB 3.2 10Gbit * 3x USB 2.0 (why?) * SPI / GPIO HDAudio #1 #1 expected ASM4242 mux with 2x DP for APUs -- It'd be nice if these pins could export additional PCIe lanes for non-APU systems. That 4.0 x 4 set of lanes is expected to service up to... * 4.0 x4 (bridged daisy) * 4.0 x4 NVMe * 4x SATA 6Gbit/sec * USB 3.2 20Gbit * 4x USB 3.2 10Gbit * 4x USB 2.0 + * 4.0 x4 (daisy to cards) * 4.0 x4 NVMe * 3.0 x1 2.5Gbit Ether * 3.0 x1 + 2.0 USB WiFi * 2x SATA 6Gbit * USB 3.2 20Gbit * 4x USB 3.2 10Gbit * 4x USB 2.0 __ideally__ they'd have done something more like x4 PCIe 5.0 for the secondary NVMe drives and downstream system ports to share, along with an x2 PCIe 5.0 link utilized for the other existing ports on the two chips.

rasz 4y ago

it will, but only if you pay extra for fake "X670E" chipset while getting same X670 motherboard, but with unlocked pcie 5.0.

paulmd 4y ago

This has been clarified by the actual presentation: X670E gets PCIe 5 on all CPU links, X670 gets PCIe 5 on the first slot and storage, B650 gets PCIe 5 only on storage. Of course, the chipset itself has nothing to do with what connectivity is provided to the PEG slots since those run straight to the CPU - this is market segmentation in action, the CPU simply won't turn on those feature-bits if you don't pay for the premium chipset. Also, as noted, on AMD the chipset has nothing to do with anything anyway. It is just an IO expander, it doesn't boot the CPU or do anything like that, and it is entirely uninvolved, out of the loop entirely, when the CPU is talking to things that are attached to PEG direct lanes.