nuno14272 wrote on 2020-12-11, 16:21:
Hello, I've just bought this socket 2 motherboard.
Thas a really strange layout. socket 2 with pci !, with IDE but no FDD ? whats happening...
socket 2 suposelly doesnt support 3,3v cpus but board as a 3,3v stamped.
You are right: Mechanically, that is a socket 2. But from functionality, it seems to be a full-featured socket 3. As the mechanical difference is just about the outer pins near the pin-1 corner, and the only processor that uses the outer ring and is actually available is the Pentium Overdrive which fits both sockets, it doesn't matter in practice that they fitted the "wrong" socket. You can easily see that this board has socket-3 functionality by finding the voltage regulator with its heatsink near the processor socket.
IDE but no FDD also made sense at that time: The UM8886 south bridge as a local-bus connected IDE controller, so it's basically "for free" (you still need space on the board for the connectors and the traces), whereas FDD, serial and parallel can be provided at full performance using ISA multi I/O cards that already were cheap commidity items in 1992. To provide these ports onboard, you would need to place a Super I/O chip, its crystal, the serial port level converters and all required connectors on the main board without any advantage in performance. On the other hand, VL IDE controllers were expensive and difficult to setup, whereas the UM8886 is soft-configurable and initialized for the correct speed by the BIOS routines provided by UMC.
