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SpinalHDL / NaxRiscv

MIT License
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Question about the sizes of cache L2 & L1 #109

Closed phillippZZ closed 3 months ago

phillippZZ commented 5 months ago

Hi, Dolu. I succeeded to simulate naxriscv with 4 cpu cores by using litex under your guidance. But later on I noticed that the size of cache L2 doesn't seem to be bigger than L1(I suppose "sram:8kb" represents the size of cache L1). Could you tell me if I forgot to specify something? Just as a reminder, I used "litex/litex/tools/litex_sim.py --cpu-type=naxriscv --with-sdram --sdram-data-width=64 --sdram-init images/boot.json --cpu-count=4" to simulate. MicrosoftTeams-image MicrosoftTeams-image (1)

Dolu1990 commented 5 months ago

Hi,

That's ok, that L2 cache is internal to litex and NaxRiscv will not read memory through it. Nax coherent infrastructure has its own l2 coherent cache which is 128 KB by default normaly.

Idealy, i would need to have it disabled automaticaly for Nax/Vexii cpus targets in litex.

phillippZZ commented 5 months ago

Oh, I see. So the "l2" option in this case is actually related the wishbone stuff. I'll disable it. Thank you very much.

phillippZZ commented 3 months ago

Hi, @Dolu1990

One more question about L1 and L2 cache. Could you please tell me the cache line sizes of both l1 and l2? I can't find the value them in the code.

Dolu1990 commented 3 months ago

Hi ^^ Always 64 bytes

phillippZZ commented 3 months ago

Got it! I'll remember it in my heart : )

phillippZZ commented 3 months ago

Hi, @Dolu1990. Thank you for the help all the time. I've finished several tests on the naxriscv and everything goes well. But I do have some questions and maybe few more in the future about the cache 😅 Given that l2 has total size as 128kb, cache line size as 64 kb and 8 ways by default, can I say that the number of sets are 256 by default? Do we set the total size, line size and number of ways of l2 cache first, and then the number of sets can be calculated automatically? Also, could you tell me the default config of L1 & L2 cache? I'm looking for the number of ways and sets of L1 and L2 cache.

Dolu1990 commented 3 months ago

sets are 256 by default?

256 is correct

Do we set the total size, line size and number of ways of l2 cache first, and then the number of sets can be calculated automatically?

yes right

L1 L2

L1 are 4 way 64 sets L2 is 8 way 256 sets