locked i-cache

By: Wilco (wilco.dijkstra.delete@this.ntlworld.com), February 21, 2020 11:33 am
Room: Moderated Discussions
Moritz (better.delete@this.not.tell) on February 21, 2020 9:32 am wrote:
> hobold (hobold.delete@this.vectorizer.org) on February 21, 2020 7:33 am wrote:
> > A number of embedded processors allow locking down (part of) their caches. So you can prime, say,
> > the instruction cache with your small function, and then lock down that part of the cache. From then
> > on, the function cannot be evicted from cache anymore. Calling it will always be a cache hit.
> > Close enough?
>
> Implementation wise very different, but with the same outcome.
> I of course thought of a CPU that did not even have caches or complex instructions that could
> do a lot of work. It would also have been an optional, backwards compatible addition.
>
> The argument that came to mind against it was that any CPU that could have profited would have been so
> tiny that even the smallest such explicit i-cache would have been a waste of expensive transistors.

Most if not all microcontrollers do this - they have no caches or DRAM but use on-chip flash and SRAM. You can store critical functions in SRAM for faster execution.

Wilco
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