A few days ago, Intel, TeamGroup, and ASRock jointly released the "HUDIMM" specification for DDR5 memory.

HUDIMM uses a single 32-bit sub-channel instead of two 32-bit channels filling the 64-bit bus as traditional DDR5 does.

This effectively halves the bandwidth and capacity, but reduces the cost of DDR5 and the number of ICs per memory module. New tests conducted today by HKEPC with assistance from ASUS confirm this – HUDIMM results in nearly 50% bandwidth loss, significantly reducing performance.

HKEPC and TeamGroup

First, it's important to clarify that HKEPC didn't receive the actual retail version of the HUDIMM kit manufactured by TeamGroup; they used standard DDR5 memory, but sealed half of the contacts with tape. This rendered one of the 32-bit sub-channels unrecognizable, thus simulating the effect of HUDIMM. A member of ASUS's R&D team had already tried this method before the launch event, as we mentioned in previous reports.

This new test is more convincing. The test platform was an ASUS ROG Maximum Z890 Extreme motherboard with an Intel Core Ultra 9 285K processor. This test "matched a BIOS that supports HUDIMM modules" because, unlike commercially available single 32-bit memory modules, the SPD of the modified dual 32-bit memory still tells the memory controller that it should use a 64-bit bus. Otherwise, the computer will fail to complete the POST self-test and encounter a training error.

We first tested a single-sided 16GB, 7200 MT/s USB flash drive, which actually displayed a capacity of 8GB. In AIDA64 testing, its read speed was 32,447 MB/s, write speed was 25,195 MB/s, copy speed was 26,894 MB/s, and latency was 87.7 ns. In comparison, the USB drive, without power, achieved read speeds of 58,913 MB/s, write speeds of 48,800 MB/s, and copy speeds of 52,648 MB/s. Throughput nearly doubled across the board, but latency remained at 85.7 ns.

As expected, disabling one of the 32-bit sub-channels almost consistently halves the bandwidth. This allows you to manufacture cheaper memory modules, requiring only 4 ICs instead of the 8 typically needed for a 16 GB DIMM, but this obviously comes at a cost. A standard 16 GB memory module has an effective bandwidth close to 60 GB/s, while an emulated 8 GB HUDIMM only achieves 32 GB/s. This is the difference you'll notice.

After switching to a dual-channel configuration, HKEPC installed two 16 GB 7200MT/s memory modules on the motherboard. The standard configuration displays 32 GB of memory, but only 16 GB is actually used. The same thing happens again: when emulating a HUDIMM, the bandwidth is halved. Read speeds drop from 106 GB/s to 58 GB/s, write speeds from 93 GB/s to 48 GB/s, and copy speeds from 97 GB/s to 51 GB/s. Latency remains unchanged.

As expected, disabling one of the 32-bit sub-channels almost consistently halves the bandwidth. This allows you to manufacture cheaper memory modules, requiring only 4 ICs instead of the 8 typically needed for a 16 GB DIMM, but this obviously comes at a cost. A standard 16 GB memory module has an effective bandwidth close to 60 GB/s, while an emulated 8 GB HUDIMM only achieves 32 GB/s. This is the difference you'll notice.

After switching to a dual-channel configuration, HKEPC installed two 16 GB 7200MT/s memory modules on the motherboard. The standard configuration displays 32 GB of memory, but only 16 GB is actually used. The same thing happens again: when emulating a HUDIMM, the bandwidth is halved. Read speeds drop from 106 GB/s to 58 GB/s, write speeds from 93 GB/s to 48 GB/s, and copy speeds from 97 GB/s to 51 GB/s. Latency remains unchanged.

Here, HUDIMM's performance is roughly equivalent to a regular 16GB single-channel memory module, which is expected. The reason is simple: we've halved both bandwidth and capacity to reduce the cost of DDR5. The performance loss is indeed significant, but considering that HUDIMM's target users are gamers and business users with limited budgets, this trade-off might be worthwhile for some.

The new HUDIMM memory specification has been introduced to address memory shortages

Thanks to the rapid development of artificial intelligence, component prices have soared in recent months, forcing users to find ways to cope with the memory shortage crisis. ASRock previously released a motherboard that supported both DDR4 and DDR5 memory slots to alleviate this problem, and now it is collaborating with Intel and TeamGroup to launch "HUDIMM"—a new type of DDR5 memory that is expected to help users save money.

DDR5 memory (UDIMM) typically uses two 32-bit sub-channels per memory module, requiring enough chips to fill the full 64-bit bus. This constitutes a single rank. HUDIMM, or semi-unbuffered DIMM, uses only one 32-bit sub-channel, effectively halving the memory bandwidth and density. This makes memory modules cheaper and requires fewer modules, essentially equivalent to a "half-rank".

ASRock, in collaboration with TeamGroup, has produced the first batch of HUDIMM memory modules, which are already compatible with Intel 600, 700, and 800 series motherboards. ASRock also manufactures HSODIMM memory modules, which are conceptually similar to HUDIMM but use an SO-DIMM (laptop/mobile device) interface instead of U-DIMM (desktop). The company targets entry-level users who don't require the highest performance or capacity.

DDR5 memory (UDIMM) typically uses two 32-bit sub-channels per module, requiring enough chips to fill the full 64-bit bus. This constitutes a single rank. HUDIMM, or semi-unbuffered DIMM, uses only one 32-bit sub-channel, effectively halving the memory bandwidth and density. This makes the memory modules cheaper and requires fewer modules, essentially equivalent to a "half-rank".

ASRock partnered with TeamGroup to produce the first HUDIMM memory modules, which are already compatible with Intel 600, 700, and 800 series motherboards. ASRock also manufactures HSODIMM memory modules, which are essentially the same concept as HUDIMM, but use an SO-DIMM (laptop/mobile device) interface instead of U-DIMM (desktop). The company targets entry-level users who do not require the highest performance or capacity.

Following ASRock's announcement, ASUS also showcased its HUDMM technology on its ROG Maximum Z890 Apex motherboard. A member of the R&D team used two standard 24GB DDR5 memory modules, sealing half of the contacts with tape, effectively disabling half of the chips. As a result, the memory capacity displayed in the BIOS was no longer 48GB, but only 24GB.

The company did not disclose whether it is also collaborating with TeamGroup to add official HUDIMM support, but a statement from an engineer may indicate that such plans are in the works. If ASUS also joins this standard, the entire industry will quickly drive its adoption, and we may soon see more affordable DDR5 memory. However, specific release dates and pricing information have not yet been announced by any party.

Source: Compiled from tomshardware

View more at EASELINK