WRX90 is AMD's workstation platform for Threadripper PRO 7000 WX and 9000 WX processors. It gives a single processor eight DDR5 memory channels, which is the reason to choose it over a desktop platform. Populating those channels correctly is simple once you know the rules, and getting it wrong halves the memory bandwidth you paid for. This guide explains the eight-channel layout, why eight identical modules is the right answer, and how to install them.
WRX90 memory at a glance
| Threadripper PRO 7000 WX | Threadripper PRO 9000 WX | |
|---|---|---|
| Memory channels | 8 | 8 |
| Slots on WRX90 boards | 8 (one per channel) | 8 (one per channel) |
| Memory type | DDR5 ECC RDIMM | DDR5 ECC RDIMM |
| Rated speed | DDR5-5200 | DDR5-6400 |
| Maximum memory | 2TB | 2TB |
The ASUS Pro WS WRX90E-SAGE SE, ASRock WRX90 WS EVO and GIGABYTE MH53-G40 all use this eight-slot layout. For the platform overview, see the AMD WRX90 memory guide.
Why eight identical modules
- Bandwidth scales with channels. Each DDR5 channel moves 8 bytes per transfer. At DDR5-6400, eight channels give a theoretical peak of about 410 GB/s; four give about 205 GB/s. There is no second slot per channel to make up the difference later.
- Identical modules keep the channels balanced. Use the same capacity, rank and speed in every slot. ASRock's WRX90 WS EVO manual asks for identical DIMMs, and mixed modules run at the slowest module's settings.
- Capacity comes from module size. With one slot per channel, the way to grow is larger modules: 8 x 32GB for 256GB, 8 x 64GB for 512GB, 8 x 128GB for 1TB.
- Fewer DIMMs only as a stopgap. If you start with four, use the four slots the board manual lists for a four-DIMM layout, which spread one module per channel across the board, and plan to add a matching four later.
One more limit is the processor. Lower core count Threadripper PRO models have fewer chiplets feeding the memory controller, and published benchmarks show them reaching less of the eight-channel bandwidth than the high-core models. Fill all eight channels either way; it is still the fastest and largest configuration the processor supports. For the background on channels, see dual vs quad vs eight-channel memory.
How to install eight-channel memory on WRX90
Step 1: Confirm processor and target speed
Threadripper PRO 7000 WX runs DDR5-5200 and Threadripper PRO 9000 WX runs DDR5-6400. Choose modules at or above your processor's rated speed.
Step 2: Choose 8 identical RDIMMs
Use eight modules of the same capacity, rank and speed, bought as one kit. WRX90 takes ECC registered DIMMs only.
Step 3: Power off and unplug
Shut the workstation down, switch off the power supply and unplug it. Wear a grounded wrist strap.
Step 4: Open all eight slots
WRX90 boards have one slot per channel, so with eight modules every slot is filled and there is no order to get wrong. Open the latches on all eight.
Step 5: Seat each module
Align the notch with the slot key and press the module straight down until the latch locks. The slots sit on both sides of the socket, so check both banks when you finish.
Step 6: Allow memory training
Power on and wait. ASUS notes that boot can take longer with Threadripper 9000 series processors because of memory calibration. Do not interrupt the first boot.
Step 7: Verify eight channels
In BIOS, confirm the total (for example, 512GB from 8 x 64GB) and that all eight modules are listed at the expected speed.
If something is not right
If the board stops on a memory code, check that every module is fully latched and that all eight are registered ECC DDR5. ASRock's WRX90 WS EVO manual lists Dr. Debug codes 53 (memory not detected), 55 (memory not installed) and 50 (invalid memory type). If the total or speed is lower than expected, reseat and recheck in BIOS. Our guide to the motherboard DRAM error light covers the general steps, and the board-specific guides for the WRX90E-SAGE SE and WRX90 WS EVO list compatible modules.
Find memory for your WRX90 workstation
- Threadripper motherboard memory, every WRX90, TRX50 and WRX80 listing.
- DDR5-6400 RDIMM for Threadripper PRO 9000 WX and all DDR5 RDIMM.
- ASUS workstation memory and ASRock workstation memory.
Frequently asked questions
How many memory channels does WRX90 have?
Eight. Each WRX90 board has eight DIMM slots, one per channel, so every slot you fill adds a channel.
Should I install 4 or 8 DIMMs on WRX90?
Eight for full bandwidth. Four modules fill half the channels, so peak memory bandwidth is half: about 205 GB/s instead of about 410 GB/s at DDR5-6400, by the arithmetic of channels times 8 bytes times transfer rate.
What memory does a WRX90 motherboard take?
DDR5 ECC registered DIMMs (RDIMM), up to 2TB. Unbuffered desktop DIMMs do not work. Threadripper PRO 7000 WX runs DDR5-5200 and 9000 WX runs DDR5-6400.
Does WRX90 support EXPO?
AMD lists EXPO support for Threadripper PRO 9000 WX processors. Running memory beyond the rated speed is overclocking, and AMD notes that operating outside specifications voids its processor warranty.
Why does my WRX90 workstation take so long to boot after installing memory?
DDR5 memory training. ASUS says boot may take longer with Threadripper 9000 series processors because of memory calibration, and its BIOS offers a DDR5 Robust Training Mode that trains more thoroughly at the cost of boot time.
Does every Threadripper PRO get the full eight-channel bandwidth?
Not always. Lower core count models have fewer CPU chiplets connected to the memory controller, and published benchmarks show them reaching less of the eight-channel bandwidth. Eight DIMMs are still the right layout, since they also maximize capacity.
Buying for more than one system
IT teams and integrators that maintain Threadripper PRO workstations can standardize on one kit per model. Request a quote with your models and quantities, or send us your system model and we will confirm the right module before you order.
Steps and rules are summarized from the vendors' published documentation; follow the guide for your exact model.