feipoa wrote on 2016-12-02, 12:58:

Curious how this board uses the same southbridge as PCI 486 boards, the UM8886. Also curious are the two northbridge chipsets: UM8891 & UM8892. I have never seen such a configuration. Any idea why UMC did that?

EDIT: Same Super I/O as a 486 board too: UM8663

The southbridge just bridges PCI to ISA. It doesn't know about the frontside bus, so it is compatible with all north bridges that use PCI as system bus. You could also pair 8891/8891 with an Intel PIIX3, I guess.

Why two chips for the north bridge? The UMC chips use a QFP case, which is limited to around 200 pins. A pentium board has a 64-bit data path, and it seems they just couldn't get enough pins on a single chip. Compare for example the Intel Saturn chipset. It consists of the "cache and DRAM controller" (CDC, 82424), a separate "data path unit" (DPU, 82423) and the System I/O chip (SIO, 82378). The CDC and DPU together resemble what we call "north bridge" today, whereas the SIO is approximately what we call "south bridge" today. For Pentium systems Intel even went three-chip: the Intel 82343 PCMC, QFP208 required two Intel 82433 LBX, QFP160 chips to form a north bridge. The original Triton (430FX) uses a similar layout. Only with the 430HX, "Triton II", Intel switched to BGA and put the whole northbridge into one BGA324 case.

Super I/Os just run off the ISA bus, so you can use the same Super I/O on a Pentium board as you used on a (late) 286 board. You wouldn't, though, as customers expect 16450-like FIFOs and EPP/ECP. But there is no reason to not re-use a late 486 Super I/O on Pentium boards.