Crazy to think that my first personal computer's entire storage (was 160MB IIRC?) could fit into the L3 of a single consumer CPU!<p>It's probably not possible architecturally, but it would be amusing to see an entire early 90's OS running entirely in the CPU's cache.
<a href="https://github.com/coreboot/coreboot/blob/main/src/soc/intel/common/block/cpu/car/cache_as_ram.S" rel="nofollow">https://github.com/coreboot/coreboot/blob/main/src/soc/intel...</a>
KolibriOS would fit in there, even with the data in memory. You cannot load it into the cache directly, but when the cache capacity is larger than all the data you read there should be no cache eviction and the OS and all data should end up in the cache more or less entirely. In other words it should be really, really fast, which KolibriOS already is to begin with.
In my case it began with 16K (yes, 16<i>1024 bytes) and 90K (yes, 90</i>1024 bytes) 5.25" floppy disks (although the floppies were a few months after the computer). Eventually upgraded to 48K RAM and 180K double density floppy disks. The computer: Atari 800.
I wonder how much faster dos would boot, especially with floppy seek times...
IIRC some relatively strange CPUs could run with unbacked cache.
Intel's platform, at the very least, use cache-as-ram during the boot phase before the DDR interface can be trained and started up. <a href="https://github.com/coreboot/coreboot/blob/main/src/soc/intel/common/block/cpu/car/cache_as_ram.S" rel="nofollow">https://github.com/coreboot/coreboot/blob/main/src/soc/intel...</a>