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From: iwanek@nttdata.co.jp
Message-ID: <50F591D39557D511B12C0090274DCEBC03B6754D@noanet03.noanet.nttdata.co.jp>
To: 9fans@cse.psu.edu
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Subject: [9fans] missing memory
Date: Tue, 22 Jan 2002 02:07:48 +0900
Topicbox-Message-UUID: 3f9d4646-eaca-11e9-9e20-41e7f4b1d025

Hello 9fans,

About a month ago, I reported a problem of getting the

    panic: exception/interrupt 14

from floppy installation. Not quite sure what I did differently (BIOS
power management setting, maybe), somehow I got through it. Now
I have new problem and would like to ask the list for help again.

My PC is a Dell Dimension 8200. This monster has a 1.6GHz
Pentium4, i850 chipset (danger here?) and 256MB RIMM. 9pcdisk
detects only 64MB of RAM. Setting MEMDEBUG to 1 in
/sys/src/9/pc/memory.c, I get

    maxmem 30000000 D0000000
    maxpa = F9DC -> 3F77000, maxpa1 = F9DC maxpa2 = 280
    00006000 00099C00 0009FC00	# rmapram
    001F9000 03E07000 04000000	# rmapram
    000D0000 00020000 000F0000	# rmapumb
    04000000 FC000000 00000000	# rmapupa

from memdebug(). I guess the range 04000000-10000000 should
be RAM but is classified as UPA (what is it anyway, and its size
FC000000?). Also I don't have rmapumbrw at all. Strange.

I read ramscan() code, and although many details of dealing with
MMU are beyond me, I can't tell why this doesn't work. If you
know anything about how to fix this problem, please let me know.

By the way, linux 2.4.something recognizes all 256MB. Here is
its idea of memory map:

    00000000000000000 - 00000000000A0000 (usable)
    000000000000F0000 - 0000000000100000 (reserved)
    00000000000100000 - 000000000FF77000 (usable)
    0000000000FF77000 - 000000000FF79000 (ACPI NVS)
    0000000000FF79000 - 0000000010000000 (reserved)
    000000000FEC00000 - 00000000FEC10000 (reserved)
    000000000FEE00000 - 00000000FEE10000 (reserved)
    000000000FFB00000 - 0000000100000000 (reserved)

Note that linux found out about this using BIOS's ACPI service
(INT 15h, AX=E820h). I think you can use this only from *real*
mode (horror...).

- kazumi