ASRock's HUDIMM Tech Aims to Slash DDR5 Memory Prices

You don't need me to tell you things are bad in the PC DIY market; everybody knows things are bad. The memory crunch, severe enough to earn the moniker "RAMageddon", has grossly inflated the prices of graphics cards, game consoles, SSDs, and of course, memory. In what we can only describe as a desperate attempt to slash PC production costs, ASRock, Intel, and TeamGroup have teamed up to present you a new class of memory product: HUDIMMs, which we can only assume stands for "half-width UDIMM".

This isn't about the physical width of the module. Instead, it's about the logical width of the memory bus. A standard DDR5 UDIMM has two 40-pin sub-channels. Eight bits in each sub-channel are used for ECC, and that leaves you with 2x 32-bits for a 64-bit memory interface per module. There's nothing stopping a memory manufacturer from only populating one of the two sub-channels, though, and that's exactly what HUDIMMs are.

The upside is that memory manufacturers can use fewer, denser memory chips to make memory modules. The memory makers are primarily manufacturing newer, high-density DRAM ICs because that's what the datacenter and AI market actually wants. There's simply no supply of low-density memory chips that would be used to populate both sub-channels on a standard DIMM, so the minimum size of a full-width UDIMM becomes 16GB or even higher. The "solution," such that it is, is to use the high-density chips and only populate one of the sub-channels.


The downside then is that you slash your bandwidth in half. Normally, each DDR5 UDIMM presents a 64-bit memory path; it takes just two of these to fill the 128-bit memory interface found on virtually all desktop and laptop CPUs. By dropping one of the sub-channels, you are narrowing the effective memory interface by half, and that, in turn, cuts your potential bandwidth by the same amount. Your fancy 6400 MT/s RAM is now performing like a stick of DDR4 at 3200 MT/s, except probably with worse latency.

Obviously, this kind of memory is not intended for gamers, enthusiasts, power users, prosumers, or workstations. What this kind of memory is meant for is the humble office PC, as well as the budget laptop your cousin buys so he has something to watch YouTube on in his sleeper cab. A modern machine with HUDIMMs won't have any less memory bandwidth than a DDR4 machine, and it will still have the benefits of a current-generation processor architecture and platform, so it's not like it's the end of the world, really.


Amusingly, ASRock offers the image above, where it claims that using a standard 16GB UDIMM along with an 8GB HUDIMM offers "higher bandwidth/lower latency" than using a single 24GB DDR5 UDIMM. This is completely plausible, as you're engaging more memory channels on the CPU, yet the numbers presented look more like run-to-run variance than anything else, and they certainly aren't indicative of a performance advantage.

In any case, Intel supports HUDIMMs on its 600, 700, and 800-series motherboard chipsets—or at least, ASRock does after a BIOS update. It's not completely clear if other motherboard vendors will hop on the HUDIMM train, but in any case, it's important to be aware that this stuff is out there. Honestly, kudos to the three companies for making sure computing remains accessible even as shortages shoot prices up to the stratosphere.