Some testing had already been done: Vista on a real Pentium/Pentium MMX will give a BSOD with the code 0x78.The BSOD only is known to affect Intel P5 family CPUs, not AMD K5/K6, Cyrix MII, or Intel P6 family CPUs, One hint comes in the form of a video which shows Windows 7 SP1 booting on a Pentium 90MHz system:
In the description, they reference KB980358, a KB article relating to the issue. As it turns out, it had been a bug that was patched with a hotfix and one that is included in Service Pack 1 for Windows 7. Another hint comes in the fact that the hotfix only updates mcupdate_GenuineIntel.dll, which presumably controls the built-in microcode updates for Intel CPUs.
Later, doing testing in Bochs' pentium_mmx preset revealed that Vista specifically threw a 0x78 BSOD when I disabled “Ignore RDMSR/WRMSR to unknown MSR register”:
After seeing this I immediately went to check Bochs’ own logging, which revealed the following line:
Code: Select all
WRMSR: Unknown register 0x8b