(And that being said, now I’m wondering whether you could force eviction and retainment into L3 cache on demand, to achieve something like memory bank switching…)
It's not really clear to me from the limited bits of info that I've read whether or not L3 is guaranteed to be accessible when doing CAR, but, if it is, you've got enough memory available to do a lot of stuff. (And even the L2 cache is starting to get pretty big on the higher-end current-gen chips.)
That's with them holding back and not adding any v-cache. If you stacked an extra 64MB on each of the 12 compute dies, you'd have 1152MB.
(This is why I compared to the SNES: if you have to map the SNES's RAM and [every bank of] the game's ROM, then you're looking at 4–16MB depending on the game. The SNES is pretty much the newest console whose games would entirely fit, I think.)
NB L3 is unified most of the time, but but with L2 you still need to distinguish between data/code.
But I found out what Itanium 2 did had a split L2 cache.
The Zen 4-based Genoa-X will have up to 1 GB of L3 cache! You could comfortably fit Windows 95 there...
So I can say with some authority that it is possible to have a complete running installation of Windows 95 in 16 megs of disk space; however I had to trim it pretty brutally to fit, so, for example, I think it had 2 fonts left, one of which was used for the widgets that display window-close boxes and so on.
The problem was that the object of the exercise was the benchmark how much quicker it was — but there wasn't enough space left to install any applications, and our benchmark tool used real applications. So, although I did several days work and I did get paid for it, the effort was at heart in vain. But in principle yes you could run Windows 95 entirely out of 16 MB of cache memory, and if you had say 32 MB of cache memory it would be no problem at all.