Anonymous Coward wrote:

50MHz is too much for PCI. I don' t even feel confident running PCI at 40MHz. Use a divider if your boards supports one (3/2 is best for 50MHz).

180MHz on the AMD chip is doable if your board supports 60MHz FSB, but not recommended as the L2 cache can't really handle it and 486 boards get too noisy to do it reliably.

What about replacing the L2 cache chips with those with tighter timings?

Yep. It was a key pin. 😒
Anyways, with that dealt with I had to trim the soldered leads underneath and place a piece of tape on a neighboring SLT chip so the interposer did not short out. Dropped it all into place with the 3x multiplier set and instead of getting no POST readout (CPU rejected or not installed) I get a 0002 2xxx error which means POST passed CPU testing and hung on the memory (which it currently has none of installed because I don't have any of the special 40-bit ECC crap it needs).

Mau1wurf1977 wrote:

Well at least in Phil's Ultimate VGA Benchmark Database Project 160MHz is the ceiling at the moment. We don't have any 50 x 3 or 50 x 4 entries.

Am5x86-P75 40 MHz 4x 160 MHz 3dbench2: 96.3 PCPBENCH/VGAMODE: 24.5 Doom: 55.66 Quake: 15.1 Biostar 8433UUD-A VER:2 Replaced RTC to DALLAS, replaced BIOS chip with flash UMC UM8886BF Modified UUD1212 BIOS from Feipoa 2-1-1-1 Cache WS, DRAM read: 0WS, DRAM write: 0WS 256KB 15ns 8MB FPM RAM 60ns PCI S3 Trio64V+ 2MB MS-DOS 6.22 / No memory managers Mau1wurf1977 VOGONS, OCAU, dosforum, Vintage Computer Forum

Link to project: Phil's Ultimate VGA Benchmark Database Project

I've got 50x3 system, worked stable through 12 years. The previous owner added huge aluminium heatsinks to VRMs and a hand-made active cooling system to S3 Trio32.

Heat is something you really need to monitor..
Had a Cx486DX/2 overclocked to 100MHz, and after the fan failed on the cpu, the chip cracked...

I've only ever seen that happen with the CPU is inserted the wrong way.