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I have been persistent with a thought to perform my first BIOS update ever through MS-DOS but have been postponing this task until today. Despite people telling me any bootable ISO will do it either through CD-ROM or RAMDRIVE, I am still having problems. First is the problem with CD-ROM driver trying to make it work with 4 driver files (cd1.SYS, cd2.SYS, cd3.SYS, cd4.SYS) as well as starting RAMDISK proved to be failure:

CD-ROM XMS Allocation Error enter image description here

RAMDISK XMS Allocaton Error (X: and R: drives not working) enter image description here

This A20 line seemed to be the obstacle which then after a couple of searches pointed me to this article on Microsoft website. It seems that FastGate is the culprit which takes over A20 line and conflicts with himem.sys which should be handling it causing the driver to be unable to allocate memory resources. Albeit article suggests 2 workarounds which is disabling FastGate option or adding switch, I read that the former workaround could cause problems which involves later tinkering BIOS, disabling shadow copy etc. while the latter workaround can just hang system as stated in the link above. I assume it just hangs the boot process from image file though.

Summing up the above, I am cautious and think it is risky to follow both workarounds because disabling FastGate or trying adding switch by trying available switches from 1-14 or 16, could crash the BIOS update process by itself. I could do this without the need for himem.sys with bootable USB thumbdrive by making it to be seen as USB-HDD, but some time ago I read that it is never a good idea to update BIOS from hard drive so even thought it is simulation, who knows... Maybe it will deactivate hard drive in the middle of the BIOS update process or even USB thumbdrive per se? This article on IBM support website recommends not to load himem.sys as it conflicts with BIOS update.

DELL Latitude E6420
8GB of RAM
Windows 7 Enterprise 64-bit


Bootable images that I have tried:

Hiren's Bootable CD
Bay Wolf's BIOS Update CD

Please note that since BIOS updates are over 5MBs, they cannot be burned in bootable 1.44MB or 2.88MB images which means CD-ROM or RAMDISK. However ImgBurn has "Custom" emulation type option in "Bootable Disc" where I don't know how to fill out last 2 fields:

enter image description here

share|improve this question
bios update is put into memory before it is actually flashed to the motherboard, no matter what media you use to flash, so the hard drive method will work and is as safe as any other method. You might explain how you made your flash disc and what brand of PC it is. – Moab Sep 6 '12 at 20:43
@Moab Question is now updated. – Boris_yo Sep 6 '12 at 22:30
  1. You could just not load himen.sys. Usually you only need it if you need to free up memory in the bottom 640KB or when you want to use the extra high memory as disk cache. The latter is not needed (heck, undesired) while doing a BIOS update. (Reason: Load is few programs as possible. Preferably only what you really need. Then there is less chance of something getting in the way).

  2. If you make a traditional bootable CDROM it will emulate a floppy disk. You do not need a CDROM driver to access this part. Granted, you will only see the 'floppy image' on the CDROM, and that limits you to 2.88MB. But that is usually much more than you need for the BIOS update program and the BSOS image.

  3. You could just use an old fashioned floppy drive. They are getting old, but some of us keep them around for just such a thing.

  4. If you need more space then 2.88MB then please add your config.sys and autoexec.bat the question. Maybe we can spot something.

share|improve this answer
BIOS updates are over 5MBs in size so no way I can burn them with 1.44 or 2.88 ISO images. Unless I choose customized option as you can see on screenshot in my updated question. – Boris_yo Sep 6 '12 at 22:32
Try it with a USB drive. – user3463 Sep 7 '12 at 5:42

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