No, I did not try the coppermine on the old Soyo board. I searched for awhile and I finally did find the page at
Tom's Hardware where I originally found the information about the voltage question. Here is a little summary.
Slot-1 vs. Socket 370
There might be quite a few of you who want to upgrade to an even faster processor without exchanging motherboard or RAM. In theory, that's no problem, as most motherboard companies offer Slot-to-Socket converter boards. Most of them allow to select a voltage between 1.3 and 2.5V (sometimes even some more), but I've not come across one which would have its own voltage regulator. This option to alter the voltage may be great for overclocking, but so far it's certainly not suited for upgrades, as your motherboard still has to provide the voltage itself. This means that a motherboard that can't go down to 1.65 V would still not be the right host for Coppermine processors. I would love to see such a better featured adapter board, as this would make upgrades up to at least 800 MHz possible.