A lot of that is the lack of SRAM scaling. There’s still quite a bit of improvements in the back end (metal traces). That aside, if foundries adopted say a 1T-1C SRAM we’d see a pretty rapid density doubling
A lot of that is the lack of SRAM scaling. There’s still quite a bit of improvements in the back end (metal traces). That aside, if foundries adopted say a 1T-1C SRAM we’d see a pretty rapid density doubling
Is 1T1C SRAM a technological thing or does it mean "persuade designers to use DRAM in the many cases where the retention contract could be timeboxed with a bit of extra thought and cross-team haggling"?
The reality is often going to be much worse than TSMC's N2 -> A14 "mixed design" 20% density increase marketing spin.
Apparently the N2 -> A14 density increase for logic is 23% (Tom's Hardware), and about 0% for both SRAM and analog.
Both CPUs and GPUs devote considerable space to SRAM (registers & cache), and are 50% or less logic, so for them the density increase will be more like 10% rather than TSMC's 20% marketing number.
MRAM is 1T, non-volatile and supposedly has nanosecond-scale write times so it naively seems like it'd be an ideal SRAM replacement. But I guess shrinking MTJ is more difficult than other components or there are some other limitations.
MRAM is more like 100ns, but yeah Intel actually offers this as part of their 16nm foundry process
> 1T-1C SRAM
Aka eDRAM? It was a thing back on 14nm node, but AFAIR not so much anymore. The 1C part is hard to get right in a way that is compatible with a logic process.
It gets confusing...
eDRAM isn't the same as 1T-SRAM, which isn't quite the same as 1T-1C SRAM...
But overall they run into the same problems that you mention; it's just too hard to get a capacitor in play.
There is Zeno Semi's Bi-SRAM, buuuut it hasn't seemed to catch on for one reason or another.
> Bi-SRAM
Looks cool, but isn't it by definition planar process-only, no FinFET for you?
I'll admit I am not well versed on this subject on any measure, but there is this [0] paper indicating FinFET is doable, although IDK if there's any sort of hand-waving or other limitations involved.
[0] - https://ieeexplore.ieee.org/document/8614555