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No. Desktops make the cost issues even worse, because supporting twice the memory bus width not only means more wires, but also a larger, more expensive CPU soc
by wtallis 3y ago
No. Desktops make the cost issues even worse, because supporting twice the memory bus width not only means more wires, but also a larger, more expensive CPU socket, and maybe a new heatsink mounting standard.
- rbanffy 3y agoShouldn’t you get more bandwidth by having all memory slots populated?
- AnthonyMouse 3y agoCurrent PC desktops have two memory channels and often four slots, because each channel has two slots. You get more bandwidth if you populate both channels, but four isn't better than two. If you wanted four channels the CPU socket would need more pins, because right now the second and third slots use the same pins as the first and second. What you could do is put some fast/wide DRAM on the CPU package. Then you could still upgrade the fast memory by upgrading the CPU, and the pins don't have to go through the socket. This should also be compatible with existing CPU sockets, and not incompatible with also having ordinary DDR in the existing memory slots. You basically get an L4 cache made out of HBM, which is available to the iGPU.
- wtallis 3y agoYou get more bandwidth by having all memory channels populated. When you have multiple slots per channel, filling all slots at best gets you a few percent better memory performance due to having more ranks of memory, but for DDR5 platforms the extra load on the memory controller due to multiple DIMMs per channel brings a big hit to the (officially supported) memory clock speeds. The fastest memory configs for a desktop currently are using one single-rank module per channel. Using one dual-rank module per channel doubles the capacity for typically a slight performance penalty.
- rbanffy 3y agoIs there any literature on this you would recommend?