Re: Breaking the 64MB barrier

Achim Oppelt (aoppelt@theorie3.physik.uni-erlangen.de)
16 Oct 1998 18:44:04 +0200


"B. James Phillippe" <bryan@terran.org> writes:

> The question is this: I had a debate with someone about the 64MB+
> memory issue with Linux. Their position is that it's a bug in the kernel,
> and mine was that it was an x86 BIOS limitation. I have two questions:
> 1.) who's right? 2.) How is it that Microsoft is able to deal with this

Both the 2.1.x series of kernels and the 2.0.36pre* kernels have no
problems detecting more than 64MB of memory. They use a new BIOS call (int
0x15 with ax = 0xe801) which doesn't have the limitation to 64MB that the
old one (ax = 0x88) used to have. (I hope I figured this right from
arch/i386/boot/setup.S - look for STANDARD_MEMORY_BIOS_CALL in the
2.0.36pre* version of that file.) I guess that answers both your questions.

> without a bootloader option, and we can't? Seems this is a sizeable flaw
> (regardless of the cause) for systems where the memory amount may be
> changed dynamically. If this is indeed a kernel limitation, what would be

Yeah. Opening the case to add/remove SIMMs is very easy, compared to a "vi
/etc/lilo.conf; /sbin/lilo". :-)

Achim

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