[citation][nom]akljk2lkl2lk2[/nom]sdram from like 15 years ago was ~10 ns latency. DDR was slower, ddr2 was slower still, ddr3 was slower still.So, no its not 10x faster, nor is it 1000x faster....It would be great to have faster latency ram. Bandwitch has been going up a lot over the last 1-2 decades, but latency has suffered for it.If its 10ns at the same bandwitch as ddr3 then that would be great. But im not holding my breath.[/citation]
[citation][nom]billyboy999[/nom]LOL... troll or ignorant at best. RAM has never been as fast as 10ns, if you're talking about total time to read a word, RAM from 15 yrs ago, or from now. Latency has not gone up much but it certainly hasn't degraded. The Pentium Pro was a CPU you could expect to find 15 years ago. Clocked at 150-200mhz, that gives it's L1 cache 7-5ns access time at best. You must be kidding if you think RAM was anywhere as fast as L1. SDRAM ran at 100MHz back then. Cas latency of 1 or 2 doesn't mean it takes one cycle to access a value.[/citation]
Latencies for system memory have been improving over the years last I checked, not degrading. A timing of say 9 on DDR3-1600 is still lower latency for that timing's operation than a timing of 3 on SDRAM that runs at 133MHz. Timings increase, but the frequency increases are enough to counteract that (although early modules of a new RAM interface often have higher latency than the previous modules of the same transfer rate, probably caused by the chips being more complex and also immature process shrinks, as they mature, they improve).
I think that billyboy999 is correct in that DRAM access latency for system RAM was never anywhere near 10ns. Iit's something like 150-250 in most systems right now IIRC, but that's probably mostly caused by the system memory being several inches away instead of several micrometers away from components in the CPU, not the difference in performance between CPU cache SRAM and DRAM. A specific timing such as CAS can get around 10ns, but I don't think that it was near 10ns with any of the older SDRAM. SDRAM had higher CAS duration than that IIRC, let alone full access time with the other timings included.
ReRAM can probably be fast enough to replace SRAM. Remember, a huge part of SRAM's performance comes from the process that it is built on. eDRAM can be pretty darned close and the difference between it and DRAM is just that eDRAM is built on the same process technologies as CPUs and such instead of the processes that are used for DRAM chips that are focused on capacity and density instead of performance. ReRAM, when manufactured in a CPU, can probably be faster than the SRAM that is currently used in the caches. Also, if ReRAM is much denser than SRAM, then interleaving and such can be used to great extents to possibly beat SRAM in at least some metrics. ReRAM might not be fast enough for L1 cache, but even if its not, then it might be great as L2, L3, or L4.