I understand that even the fastest nvme drive is way slower than RAM, but surely that isn’t the only reason we don’t see 1tb memory modules on the market. I was only able to find 512gb modules in my searching, and that was for servers.
In: Technology
Because memory modules are faster the latency of the communication lines between the processor and memory is actually important. So even long after hard drive have moved to serial interfaces the memory modules are still using a low latency parallel interface. This is why there is so many pins. Each command is sent all at once with one bit per pin. However this means that there is a limited address space. If the processor wants to retrieve the data beyond 512GB it needs to use a bit which is not there. There just is not enough pins on the memory module. The pin is actually there from the processor but instead of being sent to the memory module it is sent to the motherboard which will make sure only one of the memory modules on the channel is enabled. So using multiple modules it is possible to have more then 512GB of memory.
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