[syslinux] MEMDISK issue with OptiPlex GX280,620

Gene Cumm gene.cumm at gmail.com
Tue Jan 25 13:36:04 PST 2011

On Tue, Jan 25, 2011 at 13:36, Jason Vasquez <jvasquez at kennesaw.edu> wrote:
> Gladly yes to test, thank you.
> System used: OptiPlex GX280, BIOS A08. Results below.
> command line: initrd=images/misc/c.img BOOT_IMAGE=memdisk_memdskprobedbg
> Disk is hd0, 10404 K, C/H/S = 306/4/17 (MBR/MBR), EDD on, rw
> Using safe INT 15h access to high memory
> Code 1744, meminfo 276, cmdline 66, stack 512
> Total size needed = 2598 bytes, allocating 3K
> Old dos memory at 0x9fc00 (map says 0xa0000), loading at 0x9f000
> 1588: 0xffff  15E801: 0x3c00 0x7dc3
> INT 13 08: Success, count = 1, BPT = 0000:0000
> INT 13 DL80:
>  AH08: CF1 BL00 DL01
>  AH15: CF1 AH03
>  AH41: CF1 BXaa55 AH30 DH00
> BDA drive 80? 1, total count: 1
> Press a key to continue...
> INT 13 DL81:
>  AH08: CF0 BL00 DL00
>  AH15: CF1 AH00
>  AH41: CF0 BX55aa AH01 DH00
> BDA drive 81? 0, total count: 1
> Press a key to continue...

In my mind this is enough for comments based on Ralf Brown's Interrupt
list.  INT 13h AH 08h returns good data in CF and DL (0 versus
non-zero;  I think this is supposed to represent the number of valid
drives in type but uncertain).  INT 13h AH 15h returns valid data in
AH (0 = "no such drive").  INT 13h AH 41h (fortunately) sets CF nicely
and flips BX when it should be flipped (although AH 01 seems strange;
maybe 00 is not defined and it should be 01 for garbage drives).

Shao, I'm going to try this same version on a few machines I have and
see if the output is similar and report back with details (especially
if contrary to this).


> ----- Original Message -----
> From: "Shao Miller" <Shao.Miller at yrdsb.edu.on.ca>
> To: syslinux at zytor.com
> Sent: Tuesday, January 25, 2011 11:23:37 AM GMT -05:00 US/Canada Eastern
> Subject: Re: [syslinux] MEMDISK issue with OptiPlex GX280,620
> On 1/24/2011 23:53, Shao Miller wrote:
>> ...Other than that trivial piece, I've split the three types of probe,
>> 0x08, 0x15, 0x41, so each can yield more specific detail relevant to
>> the results for the particular sub-function.  No commits for that
>> stuff just yet, but perhaps tomorrow...
> Jason Vasquez, would you be so kind as to test:
> http://git.zytor.com/?p=users/sha0/syslinux.git;a=blob;f=memdisk/memdskprobedbg;h=430ed86de8846d494f47b8a7fbddf6a261ab8e71;hb=4a54740c4a390d6b1d1ba31c4bb4377ce00a295c
> ?  This build includes some new debugging.  Please report the new "INT
> 13 DLXX:" sections until they all begin to look the same.  They will
> start to look the same after only a few (maybe three) iterations.
> H. Peter: A second commit (yesterday saw a first commit) to my
> memdskprobe branch, which yields a bit more debugging output for our
> disk probing, iff DBG_DSKPROBE is #defined to 1.
> http://git.zytor.com/?p=users/sha0/syslinux.git;a=commitdiff;h=6632db7283564fbcf9131c2877f6a1398af81424
> - Shao Miller

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