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Reasons to still prefer an M2 for a HEDT situation, despite the article claims: * The latest Intel/AMD desktops only have two channels of DDR5, and if you put
by cjbprime 3y ago
Reasons to still prefer an M2 for a HEDT situation, despite the article claims:
* The latest Intel/AMD desktops only have two channels of DDR5, and if you put as little as 64GB RAM in them they can drop to DDR4 speeds (2DPC, dual-rank), less than 10% of M2 memory bandwidth.
* You can (surprisingly cheaply) buy an M2 with 192GB GPU VRAM, but you can't buy a DDR5 PC with the same amount. If we all start wanting to run LLMs locally that'll be a pretty big deal.
- phonon 3y ago> can't buy a DDR5 PC with the same amount. Should be available soon. https://www.techpowerup.com/306005/asus-teases-192-gb-ddr5-memory-support-on-amd-x670-chipset-motherboard https://www.techpowerup.com/306005/asus-teases-192-gb-ddr5-m...
- gautamcgoel 3y agoWhy is it that using 64GB of RAM causes bandwidth to drop?
- cjbprime 3y agoThe bandwidth is fastest with one single-rank DIMM per channel, and there are four slots and two channels, so you ideally want two single-rank (chips on one side) DIMMs total. It'll get slower with 2DPC (DIMMs Per Channel), and slower still with dual-rank 2DPC. Some people are even seeing instability, with that setup at the slow DDR4 speeds. There aren't any 32GB single-stick DDR5 DIMMs yet, let alone 32GB single-rank single-stick, so if you want 64GB then you're using four sticks of dual-rank 16GB, the worst scenario.
- gautamcgoel 3y agoThanks, this makes sense!