ASUS P4G533 BIOS

Only for programmers and BIOS gurus with technical questions.
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wolv_aaron
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Joined: Sun Sep 26, 2010 5:37 pm

I have an ASUS P4G533-LA motherboard that was in a Compaq presario S5300NX (same board and BIOS as HP Pavillion a335w) and have found that this is a "special" Award Medallion BIOS that can't be edited using normal methods. I can open the BIOS rom file in Award BIOS Editor 1.0 and get some info off of it, but there is a lot that I cannot change. It recognizes the format of the SYSTEM.ROM file, which is the main BIOS file. In the setup menu tab, I can see the BIOS options (Floppy Diskette A, CPU Frequency Multiplier, etc...) and their registers and defaults. I was reading that in regular Award BIOS files, there might be _en_code.bin and item.bin--mine doesn't have those, but I did find the same interactions between the system BIOS file and the Group2.ROM file (setup labels) that work just like those files would. The basic question that I have would be: is it safe to manually modify the lines in SYSTEM.ROM that correspond to a setting value (ie. CPU Frequency Multiplier) and re-insert that modified SYSTEM.ROM back into the BIOS with Award BIOS Editor, calculate Checksum, save it, and then flash it to the system BIOS? The code line for CPU Frequency Multiplier and what it change is listed below--some of the things I couldn't figure out exactly what they did--any explanation would be good, I was mainly interested in changing the default values and the status to make the item visible in the BIOS.

Original System.ROM
CPU Frequency Multiplier
41 00 4F 40 8C 36 00 00 4C 1F 00 64 7A 00 00 15 00 06 00 00 00 00 00 E7 65

Modified System.ROM
00 00 4F 40 8C 36 00 00 4C 1F 00 64 7A 00 00 15 00 06 00 03 00 08 00 E7 65


Byte Value (Original/Modified) what it changed in Award BIOS Editor
----- ------------------------- ------------------------------------
1 41/00 Active Status
2 00/00 ?
3 4F/4F ?
4 40/40 ?
5-6 8C36/8C36 Chipset Index (Bytes reversed-- was 368C)
7-8 0000/0000 Chipset Registers (Reversed?)
9 4C/4C CMOS Index
10 1F/1F CMOS Mask- Last Byte
11 00/00 CMOS Mask- First Byte
12 64/64 ?
13 7A/7A ?
14 00/00 ?
15 00/00 ?
16 15/15 Labels location? (Group2.ROM)
17 00/00 ?
18 06/06 Screen Position (X)
19 00/00 Screen Position (Y)
20 00/03 BIOS Default (From 8x to 12x)
21 00/00 ?
22 00/08 Setup Default (From 8x to 17x)
23 00/00 ?
24 E7/E7 ?
25 65/65 ?
edwin
The Hardware Archivist
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why people still think they can program around a hardwired lock inside the CPU is beyond me. it is not going to work. what ever you set the multiplier for in the bios, the CPU will still run at the multiplier set inside the CPU.

you need the Asus version of cbrom.
edwin/evasive

Do not assume anything

System error, strike any user to continue...
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