PCChips M506/M507(maybe M505 too)
The M506/M507 are plain std intel i430FX based boards. There are no outstanding features or problems. They make brave workhorses.
There are no known big differences between the M506 and the M507.
This board supports all single voltage CPUs.
These are the intel Pentiums, AMD K5, IDT C6/W2/W2A and some early Cyrix 6x86 CPUs.
The fastest you can put in without hardware modification, adapter sockets or a VRM, is an IDT W2A 233 MHz. My board does work fine with that CPU.
Dual voltage CPUs (intel Pentium MMX for example) can only be installed, IF you have a VR-Module for the socket (and if you got that socket and not only the solder pads!). These aren't availiable anymore. If you can get hold of one, you may be able to install any CPU, which is supported by the VRM.
The black square *Write-Back* cache chips are fake. The only place where you can install cache, is the COAST-Socket. Without anything installed there, there isn't any cache. These COAST-modules are not available anymore.
The board came with an Async-Cache module. Later I got a defective Pentium board with a Pipelined-Burst module which also worked (and was faster!).
The cacheable area of this board is 64 MB.
You can find solder pads just beside the keyboard connector. So why did they not put the headers on it? AFAIK the used UMC 8663 Multi I/O has a bug, which prevents the use of the keyboard AND the mouse at the same time.
Little is known about this board. It uses the same Bios ID. Maybe it is more or less the same board, only supporting fewer (and slower) CPUs. Looking at the i430VX based boards from PCChips, which all can use the same BIOS, there is hope, that the Bios upgrades from the M506/M507 do work on a M505 too.