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Description
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Phoenix 4.x BIOS code does not normally enable the internal CPU cache unless it can identify the CPU on bootup. Some early versions of the Intel 486DX4 Overdrive (ODP or ODPR) didn't use a CPUID as expected by the BIOS. Therefore the BIOS may not enable the internal CPU cache. Intel later changed the CPUID to the same as that for the 486DX4.

Solution

This DEBUG script will force a Phoenix 4.x BIOS to recognize a DX4 Overdrive CPU. It is actually programming CMOS RAM to set the CPU type to a 486DX4, which will cause the BIOS to enable the internal CPU cache. This must be rerun if CMOS RAM is lost.
Start your PC in DOS mode. Then type:

C:\>DEBUG
- o 70 34
- o 71 E4
- q (quits to DOS prompt)
C:\>

You must reboot system after running above script for it take effect.