DIMM voltage selector jumper, 168-pin, 3.3V/5V

I have a PCChips M571 socket 7 motherboard which has two DIMM sockets
and 4 SIMM sockets. The 168-pin DIMM sockets have an associated DIMM
voltage selector jumper which allows a choice between 3.3V and 5V. The
SiS 5597/5598 chipset accepts both SDRAM DIMMs and FPM/EDO DIMMs. Both
DIMM sockets are marked "3.3V" and "UDRAM", which suggests that the
two notches accommodate regular 3.3V unbuffered DIMMs. This begs the
question, were there ever any DIMMs (perhaps FPM/EDO ?) that required
5V but which came in a 3.3V form factor?

BTW, a PCChips M572 motherboard based on an Intel i430TX chipset uses
a similar memory arrangement and has the same voltage selector jumper.

- Franc Zabkar
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