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Discussion Starter · #1 · (Edited)
Hello everyone,

If you already know this procedure for the P4x800x series motherboards, great. The instructions in your mobo manual are correct. But the instructions on the Asus Download site ("BIOS Update Step: How to Flash Your BIOS") are out of date.
Here is one working procedure:


The version is in your POST display, not your BIOS "System Information" display. Power up or do CTRL+ALT+DELETE. Wait 1 or 2 seconds, then hit DELETE. If you have the colored Asus banner enabled, this should switch the display to POST output you couldn't see before. In this POST output you should see that the top few lines look like this...

AMIBIOS (C)2003 American Megatrends, Inc.
ASUS P4C800-E ACPI BIOS Revision 1010
CPU: Intel(R) Pentium(R) 4 CPU 2.80GHz

: etc...

If you missed it, try again but a couple seconds after DELETE, hit the PAUSE/BREAK key on the keyboard. With most AMIBIOS, as with these mobo's, this action stops the POST, freezing the display so you can read it. With enough repetitions you can even view all your POST output! Afterward, you need to do CTRL+ALT+DELETE again to start over.

So there's the version Asus is talking about (they never tell you this on the website, and AFUDOS doesn't have a reporting feature like AFLASH does). The output blanks pretty quickly, replaced by the Promise scan. After the update, in the Setup's "System Information" screen, the date will change but the version number stays the same-- and it's not the version number you need.

EZ Flash should only be used to return to the original, factory-installed version which you will save in the steps below. Use of EZ Flash (ALT+F2 method) to update to a new BIOS is NOT recommended, as results have been hit-and-miss.

Internal BIOS formats changed in late 2003, and it took several releases to get EZ Flash working again. The ROM-resident EZ Flash code on many older mobos is incapable of installing the newer type of BIOS, and some aspects of your mobo will not function correctly after attempting this.

If recovery of a dead BIOS is necessary, use EZ Flash to return to the factory condition. Then use AFUDOS to perform any updates.

  1. First create 2 bootable floppies,one for your backup and one for your update. You need two since the files are so large. Label the first floppy "original BIOS auto recovery" and label the second floppy "ASUS BIOS Update 1010" or whatever.
  2. Download the desired BIOS update from the Asus download site. Make sure you get the BIOS for your exact mobo model name. Unzip all downloaded files onto the second floppy. Let's say there is a file named P4P1010.ROM; this will be your actual BIOS binary.
  3. AFUDOS is the program which saves and updates the BIOS. (We do not use Aflash.exe for this series of mobo's.)

    As of this writing, the latest version is AFUDOS v2.07. Usually you should download and use this version. It is not known how compatible this version is with very old BIOS, but it should definitely be used for all the newest updates.

    For some BIOS versions (e.g. P4C800-E v1014) an AFUDOS version is included in the BIOS zip file; use that instead of other earlier versions you may still have lying around. Copy the AFUDOS from the second floppy (created in step 2.) to the first floppy.
  4. After downloading AFUDOS, unzip it, and add the extracted content onto both floppies.
  5. Write-protect the second floppy, which contains your new BIOS version.

  6. BACKUP:
    Now boot from the first floppy. At the A: prompt do the command,
    "afudos.exe /oP4P800.ROM" without the quotes, with a blank between the .exe and the /o, but with no blank between the /o and the filename. The current BIOS will be copied to this floppy. It takes about 30 seconds.

    for P4P800 Deluxe or P4P800 non-Deluxe, use the file name P4P800.ROM;
    for P4P8X use name P4P8X.ROM;
    for P4C800 non-deluxe use name P4C800B.ROM;
    for P4C800 Deluxe use name P4C800.ROM;
    for P4C800-E Deluxe use name P4C800ED.ROM;
    for P4P800-VM use name P4P800VM.ROM;
    for P4P800S use name P4P800S.ROM;
    for other mobo models, check your manual for the name to use).
  7. Now write-protect this first floppy, which contains your backup factory BIOS.

    The filename above is special, such that later on if you should ever get a BIOS "checksum error", you can recover like this:
    (a)Stick the first floppy in the drive (the one containing your saved factory BIOS. Power up, then hit ALT+F2 for Recovery.
    (b)the original BIOS will be automatically reloaded by the mobo's built-in, ROM-resident "EZ Flash" utility (not the same as Aflash.exe).
    (c)hit DELETE during the POST selftest to get into the BIOS Setup.
    (d)visit Exit- Load Default Settings, confirm, and hit F10 to save.
    (e)(optional) run AFUDOS to update to newer versions of BIOS if needed; each time, visit Exit- Load Default Settings.
    (f)reapply any of your custom settings. Hit F10 to save.

    IMPORTANT: Do not use EZ Flash to "update" to new BIOS, only to recover the original factory BIOS so you can get going again. See warnings above.

    It appears auto-recovery does not require a bootable floppy, but in case you ever wish to backdate the BIOS under DOS, it still needs to be bootable.

    When you get ready to update, reboot and hit DELETE during the POST selftest to get into the BIOS Setup. Go through ALL the screens and write down ALL your custom settings. Hit ESC to exit.
  10. Now reboot from the update floppy, and at the A: prompt do the command,
    "afudos.exe /iP4P1010.ROM", without the quotes and with a blank between the .exe and the /i, but with no blank between the /i and the filename.

    The new BIOS will be installed, programming it into the flash memory. It takes about 45 seconds. The system will then automatically reboot.
  11. DO NOT "clear the CMOS" after this, you should never have to do that (if you ever do, realize you need to take the battery out before the 15-sec. clearing).
  12. Again hit DELETE during the POST selftest to get into the BIOS Setup to make your changes. First visit Exit- Load Default Settings, then reapply any of your custom settings. The reason you Load Defaults first, is to make sure any new config fields they added since the last rev, are not left uninitialized.
  13. Hit F10 to save, confirm, and exit.


19Sep2003- added version check info.
23Sep2003- added P4P8X filename.
09Oct2003- clarify blanks are needed after .exe, and add P4C800 non-Deluxe. Discuss EZ Flash.
23Oct2003- cleanup vers num discussion, mention F10 and battery.
15Nov2003- added P4P800VM filename.
02Dec2003- reorder to handle new bundled AFUDOS, revise non-boot recovery floppy note.
08Jul2004- add P4P800S, update AFUDOS section, more EZFlash info, cleanup.

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I have bought new Asus P4P800 Deluxe and have got Bad BIOS checksum during starting up for the first time. I did managed once to read P4P800.rom from support cd and it started flashing ... process but nothing happened.

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Any ideas would help.

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