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Celeron 2GHz Cache Detection?

Posted by Cliff on from the matching-what's-reported-with-what's-really-there dept.

EAJoe asks: "I have small problem with one Celeron 2GHz machine. Linux kernel 2.4.18-24.7 doesn't seem to switch L2 cache on! This CPU apparently _has_ 128K of L2. There is nothing about L2 in the logs, and /proc/cpuinfo shows an L1D size of 8K instead. Of course I have enabled L2 in BIOS settings (the motherboard is an ASUS P4S533-E, by the way). The CPU overclocks easily up to 3.5 GHz, running stable at 3 - it seems that cache is really switched off. At 3 GHz g++ compilation times are similar to Athlon XP 1800+ machine. I don't have windows on this computer to check this out, but Intel DOS utility shows a Celeron 2000 w/128k L2, also there is '128K' written on the CPU's die. Any suggestions?"

4 of 28 comments (clear)

  1. Possible solution and directions to go from here. by Manax · · Score: 4, Insightful
    Maybe you should do a little Google search.

    The first link that returns is an old kernel patch, specifically for enabling the L2 cache on a Celeron, although with "powerleap", whatever that is. That is something to try though, just make sure you have a backup kernel to boot from.

    Also, there was a post to lkml with a similar question here without a solution.

    If you don't find a solution, the best place to post isn't slashdot but to LKML.

    --
    "Why should I be content to simply live in this world, when I, as a human being, can CREATE it?" - Oertel
  2. compilation times without a cache? by YE · · Score: 2, Interesting

    Hmmm, I doubt that without the L2 cache compilation times would be anywhere near the Athlon 1800+. More like an Athlon 180+. Compilation is a very random-memory-access process, so it would kill the P4 core with its relatively large memory latency without a cache.

    Try running a test that repeatedly accesses a block of memory 124, 125, 126, 127, 128 etc. KB in size. If you see a significant drop in speed when the block size grows above 128, you probably have your cache.

    Anyway, is it the _kernel_'s job to turn on the cache? Isn't that supposed to be the BIOS' job?

    1. Re:compilation times without a cache? by Manax · · Score: 2, Informative
      You should be able to see the actual cache size that linux sees via /proc/cpuinfo, look for "cache size".

      I agree, it should really be the BIOS' job to turn on the cache, and there were some references to buggy BIOSes in the minor searching I did.

      --
      "Why should I be content to simply live in this world, when I, as a human being, can CREATE it?" - Oertel
  3. Re:Possible solution and directions to go from her by Build6 · · Score: 2

    although with "powerleap", whatever that is

    "Powerleap" probably refers to the device sold by the company, that allows you to mount certain proc types on motherboards that wouldn't accept them otherwise, either because of different pinouts or whatever reason (IIRC even one where the voltages were different?), within certain limits (I don't think they sell anything that allows you to plug an 486 into a Socket A slot :-).