dionb wrote on 2025-11-07, 20:48:
He did - Intel Monaco aka Advanced/MA, an i430FX LPX board with PLB, So5 and on the PCB a place for a VRM - which is exactly the setup that Necroware designed his VRM for. So in terms of voltage it should work. There might be multiplier issues as he mentions in the link, plus fix (a judiciously placed 10k resistor).
Monaco was a code name for it. And AST had both AST Bravo MS and AST Bravo MS-T boards that you'll find referenced both to Intel 430FX and VLSI VL82C591/593 chipsets. So any part numbers or revisions would help.
Necroware has videos he linked in from the Github I posted. They go through talking about the header. It would be a very good idea to review what he did and verify the pinout is the same. You don't want to end up frying a board or CPU sending 12V somewhere it doesn't belong.
P55C are socket 7 CPUs, which have an extra pin that's not electrically connected to prevent you from using it in a socket 5 board. So that pin will need to be removed. If you look at a socket 5 socket, the corner that's pin 1, the inside has corner has three pins in a row while the other three corners have the center pin missing. One socket 7, the corner opposite pin 1 has that middle pin filled in.
A Pentium MMX should be fine with the multipliers as that board is running at 200Mhz which is 3x. The 233 MMX uses 1.5 to signify 233Mhz, it's when you get higher clocked AMD K6 processors that you could run into multiplier issues.
The unknown once you get an external VRM module working, and modify a CPU to make it work in a Socket 5 board, is then seeing if the BIOS throws a fit. It will likely just misidentify the CPU. But it could potentially refuse to post.
