3 ms·
Why is RAM not put on the CPU chip?
- enz 7y agoDoes L1-L3 cache can be considered as a sort of bistable RAM?
- ThrowawayR2 7y agoIn some sort of technical sense, yes; it's made out of SRAM and one could have the cache be mapped exactly to a block of memory that is the same size as the cache. In a practical sense, no, because it's structured as cache and accessing it is more convoluted than direct access to a bare block of memory. See https://en.wikipedia.org/wiki/Cache_placement_policies https://en.wikipedia.org/wiki/Cache_placement_policies for a description of the various types of cache structures.
- karmakaze 7y agoIf you never loaded addresses outside of the cached memory locations either explicitly or speculatively then without invalidation you could run entirely in L3 so it would be serving as storage rather than cache RAM.
- rwmj 7y agoInterestingly we were working with a start-up which was trying to go in the other direction. They want(ed) to locate RAM in dedicated servers away from compute, rather like storage is today centralized in NASes. Of course it requires insanely fast network interconnects. (I'm not claiming this is a good idea, I'm actually rather sceptical, but pointing out that there are companies trying this)
- truth_seeker 7y agoUpmem did exactly the reverse. They put CPUs inside Memory https://news.ycombinator.com/item?id=20766283 https://news.ycombinator.com/item?id=20766283