AMD Ryzen Server the ASRock Rack 1U4LW-B650/2L2T Review

ASRock Rack 1U4LW B650 2L2T AMD Ryzen 9 7900 Being Installed
ASRock Rack 1U4LW B650 2L2T AMD Ryzen 9 7900 Being Installed

The ASRock Rack 1U4LW-B650/2L2T is perhaps one of the most interesting servers you will see this year. Simply, it allows one to use the AMD Ryzen 7000 series AM5 CPUs in a 1U form factor with built-in server features like a BMC, 10Gbase-T networking, and non-ECC/ ECC DDR5 UDIMM support. At the same time, if you saw our initial Ryzen 7000 series coverage, you may think that it is a good processor series for gaming, but not for servers. We fixed that. After using this server, all I can say is, we will be using this platform.

Video Version

There have been a few products I have been so excited for, but once I saw the power and performance numbers from the server come back, I had to film the video at 4:45AM before coffee just to contain myself.

As always, we suggest opening this video in its own browser, tab, or window for the best viewing experience.

We are going to do something different with this review and start with our internal hardware overview. Page 2 is the external overview. Page 3 will be the topology, management, and performance. Then on the final page, we will have power consumption and more. This is a bit different, but I wanted to surface a key insight on Page 1.

ASRock Rack 1U4LW-B650/2L2T Internal Hardware Overview

Here is a look at the server to help folks orient themselves.

ASRock Rack 1U4LW B650 2L2T Internal Server Overview
ASRock Rack 1U4LW B650 2L2T Internal Server Overview

Behind the drive backplane, we have a set of five fans. They are not easily hot-swappable since they are cabled, but that is very common on 1U servers just due to size and cost constraints. From the system photos, you may notice that there are spaces for up to eight fans, but some of them would be hard to use given the cabling.

ASRock Rack 1U4LW B650 2L2T Fans With Shrouds
ASRock Rack 1U4LW B650 2L2T Fans With Shrouds

Inside the server, we have the ASRock Rack B650D4U-2L2T/BCM motherboard.

ASRock Rack 1U4LW B650 2L2T B650D4U 2L2T BCM Motherboard
ASRock Rack 1U4LW B650 2L2T B650D4U 2L2T BCM Motherboard

The big feature of this motherboard is the Socket AM5 (LGA1718 ) for the AMD Ryzen 7000 series of processors.

ASRock Rack 1U4LW B650 2L2T AMD Ryzen 9 7900 Being Installed
ASRock Rack 1U4LW B650 2L2T AMD Ryzen 9 7900 Being Installed

While we have been testing the server, TDP specs have changed a bit. We wanted to, however, offer this guidance:

  • There is probably a “cool” way to run this using something like an AMD Ryzen 9 7950X.
  • The game-changer way to run this server is using the AMD Ryzen 9 7900, a 65W TDP part.

While one loses some top-end performance, we were stress testing this system at 45-47C load temperatures with the Ryzen 9 7900. The gaming-focused “X” parts are using a lot more power to hit higher clock speeds for gaming. The 65W TDP parts still hit very high clock speeds, but at under 100W of package power maximum. We tried a number of different CPUs, and to us, the Ryzen 9 7900 was just spectacular on this platform. We normally do not give CPU guidance, but this was a fairly eye-opening one.

ASRock Rack 1U4LW B650 2L2T CPU And Memory Installed
ASRock Rack 1U4LW B650 2L2T CPU And Memory Installed

The other major feature is memory support. One can use consumer non-ECC DDR5 UDIMMs (so long as they fit in the 1U server.) The bigger feature is that these can also use ECC DDR5 UDIMMs, as we have here. We have heard that people that have bit flippers to introduce memory errors are seeing those errors logged in this platform.

ASRock Rack 1U4LW B650 2L2T 4x DDR5 DIMM Slots 1
ASRock Rack 1U4LW B650 2L2T 4x DDR5 DIMM Slots 1

To us, this is the game-changing combination, the 65W TDP AMD Ryzen 9 7900 and the ECC UDIMM.

ASRock Rack 1U4LW B650 2L2T 32GB Micron DDR5 ECC UDIMM And AMD Ryzen 9 7900
ASRock Rack 1U4LW B650 2L2T 32GB Micron DDR5 ECC UDIMM And AMD Ryzen 9 7900

Our readers may have noticed the ECC UDIMM is a Micron one. We purchased the ECC UDIMM for this project, but we were also doing the Micron DDR5 ECC RDIMM piece, so this is the same memory we used to show the big differences between RDIMM and UDIMM ECC memory in the DDR5 era.

Aside from the CPU and memory, we also get a few expansion slots. The PCIe Gen5 x16 slot is at the intersection of the Broadcom 10GbE chip/ heatsink and the AMD B650 chip/ heatsink. This is the slot used to service the riser making the spec on the riser slot only Gen4 x16. There is also a PCIe Gen4 x1 slot that is not used in this system. The M.2 slot is a PCIe Gen5 x4 slot but it only supports M.2 2280 and 2242 not 110mm 22110 because of the B650 chipset heatsink.

ASRock Rack 1U4LW B650 2L2T PCIe Slots M.2 And B650 Chipset
ASRock Rack 1U4LW B650 2L2T PCIe Slots M.2 And B650 Chipset

The x4 slot is effectively not used in this system. It is a PCIe Gen5 x4 slot, but we wish that ASRock had a riser to add a M.2 drive support or something to that slot to make it useful.

ASRock Rack 1U4LW B650 2L2T LGA1718 Socket Open
ASRock Rack 1U4LW B650 2L2T LGA1718 Socket Open

Overall, this is a system much like we saw in our ASRock Rack X570D4U-2L2T review, just with several updated features for the new generation that combine to make a big difference.

Now, let us get to the server’s external overview.


  1. Patrick, you say the CPU matters. Does this mean that the motherboard does not have the usual options to set a custom (lower) power limit? If it does have that option, it might be even better in terms of the flexibility it offers. Particularly for home lab setups that would be a nice feature.

  2. Hopefully there is the “Eco Mode” option in the bios, or a way to manually recreate it so you can run the X series chips at a reasonable power limit, but still have the option to let it run hot if needed?

    Any word on availability and pricing?

  3. Regarding Joriks question:

    Is ECO mode available in BIOS like on all desktop boards?

    That would allow anyone to bring TDP down to low levels on -X CPUs(105W for 7950X) in a very safe and easy way. Even simpler than setting TDP manually.

  4. Exciting! Patrick, I pulled the mainboard user manual but it only says “frequency and voltage” are in the overclock section (no details given). Can you advise if one can dial in a maximum power (watts) or amps (e.g. via PBO or Curve Optimizer)?

    A 7950x, power limited to ~95-105W actual max socket power would be killer in this system if one needs the cores.

  5. If the motherboard allows you to set TjMAX, then that could also be a very practical lever to pull. On the 7000 series the boost algorithm seems to be quite adept at taking the programmed thermal constraint into account, it is not a hard thermal throttling of yesteryear.

    Setting TjMAX to, say, 75 °C should greatly reduce power consumtion in a way that will actually adapt to changes to ambient temperature.

  6. Platforms like this are very appealing for the price/performance/power figures. Let me just get right to my question: 32GB DDR5 UDIMM sticks are a known quantity. Apparently 48GB sticks were recently released as well. What does the future hold for 64GB (or 72/96GB) modules? What does STH (and its readers) think the limit will be for ECC UDIMM module size and when? Related question: DDR4 UDIMMs have topped out at 32GB and we will never see larger, correct?

  7. Looking at the product page for just the motherboard it says the x16 slot is PCIE 5.0, seems like it’s 4.0 on this server though. Is that just the riser being 4.0 I wonder?

  8. @AustinP
    I think 64 GB DDR5 UDIMMs will surely be made, but it will take a while. Much like SRAM, DRAM density is also pushing up against the walls of physics and silicon harder than ever. You can only make the capacitors so thin and the electrons so few before your DRAM turns into a hardware RNG device. We are almost certainly in the diminishing returns era of DRAM manufacturing.

    AFAIK DDR4 is slowly creeping towards being phased out, there is negligible chance that anyone will make higher density DDR4 DRAM chips now.

  9. Doesn’t the Xeon E series lack RDIMM support anyways?
    When compared against that… I don’t think theres anything missing in the actual spec sheets anymore vs the Xeon E series.

  10. As it was not mentioned, one would assume this suffers the same issue list as other am5 mobos if you put 128GB of RAM in the slots?

  11. Now I’m interested (and sold), this server could fit perfectly for a devlopment env, or even homelab.

  12. The problem with Ryzen 7000 (and Intel 13000) is that enormous single x16 pcie5 slot. Nobody outside the hyperscalers needs that slot. The solution to that is splitting it to x16/x0 or x8/x8 depending on what is populated. This ‘server’ does not fix the problem.

  13. I hope to see more Ryzen server motherboards like the one in this server. Like other commenters, I’d like to see more PCIe slots. Also would like to accommodate 110mm M.2 and large low noise heatsink/fan for use at home. uATX / ATX layout would be great. I’d prefer to skip the integrated 10G, I’d want SFP+ anyway. Give me an extra PCIe slot to install what I want instead.

  14. I have been using 5950x server for some time … very fast.
    I am very curios to see how this gen is performing.

  15. This really is a pedestal board, not a 1U board. You can find boards (for other CPU sockets) where much of the PCIe is brought out in x8 cabled sockets. SFF8654, SlimSAS, not sure I remember the name correctly. These boards are good for 1U: you can wire up nvme backplanes, or run a load of SATA if the board is made right.

    Anyway the PCIe lanes on this thing are mostly wasted by the case form factor. People who want a home Ryzen 7000 server: build a pedestal or 2U or 4U server using this board, you will have a much more useful machine.

  16. ASRock Rack does have some interesting M.2 risers for 1U platforms. Like the RB1U2M2_G4 and RB1U4M2_G4. I would be curious so see multiple RB1U4M2_G4 models in a 1U tested. Could be nice for space starved homelabs.
    Wish the 2 drive model was 8x instead of 16x.

  17. Tested the non 10G version of this board yesterday (B650D4U) with Ryzen 7950 cpu and dynatron 1U watercooling, power is impressive (61500 cpu marks) but power draw is peaking at 325 watts for the whole server during geekbench 6..
    With upgraded fans, the Dynatron handles it quite well (83 – 89°), still 325watts is a lot in datacenter environnement.
    Will order a 7900X cpu to compare powerdraw and benchmark results.

  18. Does anyone know if the x16 slot supports bifurcation? I didn’t see anything in the manual about it but figured I’d ask. Getting one of these is mighty tempting, I just wish it had a little more PCIe.

  19. Does anyone have confirmation on whether the Broadcom BCM57416 supports NBase-T speeds? From what I’ve seen it does not, but I’m hoping someone with experience can confirm one way or another.

  20. Patrick (or anyone with hands on experience), you reference the noise of the unit briefly, but don’t show it in the video. Just how bad is it?

    We currently use Dell Precision 3930 Rack workstations for field deployments, and I think this with a 7900 would make an excellent next step up in CPU performance. But we do operate in close proximity to the servers. The Dells are practically silent in less than 60% lost.

  21. Hi Patrick,

    I would be interested in the total power consumption using the 7950@105W (ECO). Would this be possible?

  22. My only problem with your reviews is that you do not mention anything about what “server” OS you are testing these with and what kind of issue or not that you have had with installing said OS. Please expand into the OSes that will run on these hardware platforms, specifically server OSes. – Thank you.

  23. This is really an impressive piece! We got one from local disti in Australia ( and thinking to order another one. Apparently more units coming end of July, if anyone is from down under

  24. @netswitch
    What mounting bracket and upgraded fans are you using?
    I cant seem to find a compatible bracket for AM5 for this cooler, only AM4

  25. IOMMU groups

    [ 0.405364] iommu: Default domain type: Translated
    [ 0.405364] iommu: DMA domain TLB invalidation policy: lazy mode
    [ 0.423218] pci 0000:00:01.0: Adding to iommu group 0
    [ 0.423235] pci 0000:00:02.0: Adding to iommu group 1
    [ 0.423246] pci 0000:00:02.1: Adding to iommu group 2
    [ 0.423257] pci 0000:00:02.2: Adding to iommu group 3
    [ 0.423272] pci 0000:00:03.0: Adding to iommu group 4
    [ 0.423286] pci 0000:00:04.0: Adding to iommu group 5
    [ 0.423303] pci 0000:00:08.0: Adding to iommu group 6
    [ 0.423313] pci 0000:00:08.1: Adding to iommu group 7
    [ 0.423323] pci 0000:00:08.3: Adding to iommu group 8
    [ 0.423343] pci 0000:00:14.0: Adding to iommu group 9
    [ 0.423356] pci 0000:00:14.3: Adding to iommu group 9
    [ 0.423408] pci 0000:00:18.0: Adding to iommu group 10
    [ 0.423418] pci 0000:00:18.1: Adding to iommu group 10
    [ 0.423428] pci 0000:00:18.2: Adding to iommu group 10
    [ 0.423445] pci 0000:00:18.3: Adding to iommu group 10
    [ 0.423455] pci 0000:00:18.4: Adding to iommu group 10
    [ 0.423471] pci 0000:00:18.5: Adding to iommu group 10
    [ 0.423482] pci 0000:00:18.6: Adding to iommu group 10
    [ 0.423491] pci 0000:00:18.7: Adding to iommu group 10
    [ 0.423502] pci 0000:01:00.0: Adding to iommu group 11
    [ 0.423513] pci 0000:02:00.0: Adding to iommu group 12
    [ 0.423523] pci 0000:02:01.0: Adding to iommu group 13
    [ 0.423534] pci 0000:02:02.0: Adding to iommu group 14
    [ 0.423544] pci 0000:02:03.0: Adding to iommu group 15
    [ 0.423555] pci 0000:02:04.0: Adding to iommu group 16
    [ 0.423565] pci 0000:02:08.0: Adding to iommu group 17
    [ 0.423577] pci 0000:02:0c.0: Adding to iommu group 18
    [ 0.423587] pci 0000:02:0d.0: Adding to iommu group 19
    [ 0.423590] pci 0000:04:00.0: Adding to iommu group 13
    [ 0.423593] pci 0000:05:00.0: Adding to iommu group 14
    [ 0.423596] pci 0000:06:00.0: Adding to iommu group 15
    [ 0.423599] pci 0000:07:00.0: Adding to iommu group 15
    [ 0.423603] pci 0000:09:00.0: Adding to iommu group 17
    [ 0.423606] pci 0000:09:00.1: Adding to iommu group 17
    [ 0.423608] pci 0000:0a:00.0: Adding to iommu group 18
    [ 0.423611] pci 0000:0b:00.0: Adding to iommu group 19
    [ 0.423622] pci 0000:0c:00.0: Adding to iommu group 20
    [ 0.423645] pci 0000:0d:00.0: Adding to iommu group 21
    [ 0.423658] pci 0000:0d:00.1: Adding to iommu group 22
    [ 0.423669] pci 0000:0d:00.2: Adding to iommu group 23
    [ 0.423679] pci 0000:0d:00.3: Adding to iommu group 24
    [ 0.423690] pci 0000:0d:00.4: Adding to iommu group 25
    [ 0.423701] pci 0000:0d:00.5: Adding to iommu group 26
    [ 0.423712] pci 0000:0d:00.6: Adding to iommu group 27
    [ 0.423722] pci 0000:0e:00.0: Adding to iommu group 28
    [ 0.649911] perf/amd_iommu: Detected AMD IOMMU #0 (2 banks, 4 counters/bank).

  26. What about TPM 2.0 supported by VMware? we have a tried the TPM-SPI 2.0 but VMware didn’t accept with internal error message. Anyone know the exact proper bios configuration? running bios 10.18


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