Re: wrong information about cache size in linux/Configure.help

Andrew E. Mileski (aem@aem.ott.hookup.net)
Mon, 2 Sep 1996 16:46:03 -0400 (EDT)


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> To whoever is responsible for this section in linux/Configure.help, as
> of 2.0.16:
>
> Limit memory to low 16MB
> CONFIG_MAX_16M
> [..]
> You also need at least 512kB of RAM cache if you have more than 64MB of RAM.
> [..]
>
> As it is stated, this must be (and is) plain wrong. The amount of
> cachable RAM depends on the chipset, cache organization, size of tag RAM
> etc. (In the case of P6 systems with on-chip L2 cache, there's no way to
> upgrade the cache ;)
>
> Could somebody with the proper knowledge change this, clarify it and/or
> maybe add a file Help_my_computer_is_slow_after_upgrading_RAM :^), or a
> hint to the FAQ.

Here is a copy of the message I posted to linux-smp recently...

============

The following info comes DIRECTLY off the Intel datasheets.

Intel Cacheable Supported
Chipset RAM RAM
======= ========= =========
430FX 64Mb 128Mb
430HX 512Mb* 512Mb
430MX 64Mb 128Mb
430VX 64Mb 128Mb
440FX 64Gb+ 1Gb
450GX 64Gb+ 4Gb
450KX 64Gb+ 512Mb

* The amount of cacheable memory depends on the amount of tag address RAM
installed (8 bits = 64Mb, 9 bits = 128Mb, 10 bits = 256Mb, 11 bits = 512Mb).

+ Pentium Pro processors have an internal cache (it is a separate chip mounted
next to the CPU chip in a dual cavity package), hence the chipset doesn't
have anything to do with caching.

Some details on Intel products can be found on their web site at:
http://www.intel.com/design/
Or can be found in the datasheets and manuals available from the
Intel Literature Department.

- --
Andrew E. Mileski
mailto:aem@ott.hookup.net http://www.redhat.com/~aem/
Linux Plug-and-Play Project Leader http://www.redhat.com/linux-info/pnp/
PGP public keys are available from http://www.redhat.com/~aem/pgp-keys.txt

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