Re: Breaking the 64MB barrier

david parsons (o.r.c@p.e.l.l.p.o.r.t.l.a.n.d.o.r.u.s)
16 Oct 1998 10:17:37 -0700

In article <linux.kernel.Pine.LNX.3.96.981015173635.21405A-100000@earth.terran.org>,
B. James Phillippe <bryan@terran.org> wrote:
>Greetings,
>
> I am aware that passing the "mem=XX" option in LILO overcomes this
>problem; this is irrelevant because it has nothing to do with what I'm
>about to ask (for you rapid-reply "RTFM" people).
>
> 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?

Both of you are. Prior to 1.2.13[1], the only way to detect memory
was bios call 0x88, which isn't guaranteed to return anything more
than 16mb (Compaqs) or 64mb ('most everybody else). If, instead,
you use different bios calls or grub around in the CMOS memory, you
can usually[2] find out just how much memory the machine actually has.

>2.) How is it that Microsoft is able to deal with this
>without a bootloader option, and we can't?

Linux can, since 1.2.13[1].

____
david parsons \bi/ MEM= is for the birds [3].
\/

[1: For people who haven't killfiled me and who are also willing to
patch their kernels.]
[2: with the current kernel scheme, EISA machines are a glaring
exception, as well as machines that don't support bios call 0xe801.]
[3: With the exception of my HP Omnibook, which doesn't support 0xe801.
Sigh.]

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