Yeah, as far as I know, the VIAs are the only ones with support for on-the-fly multiplier changes. I don't know how far this extends, but I'm certain that any of the KT400 mobos have support. As far as any of the newer ones go, you might look at laptops and compare base chipsets.
Soft multipliers are accessible by some boards. AFAIK, no boards support PowerNow voltage changing.
Operability of soft multipliers is not just determined by chipset. BIOS brand determines how the motherboard handles soft multipliers.
Of the boards that can use soft multipliers (some boards don't work at all), those with AWARD bioses use the CPU's L3 bridges setting for the default POST speed. Those with AMI BIOSes use the L6 bridge setting for default POST speed. (That's only if the CPU is a mobile or has been "mobilized". Note L6 bridges are preset to 24X). In either case the L6 setting determines the maximum Soft Multiplier.
POST speed becomes an issue. Say you have a legacy motherboard and you are limited on max FSB speed. All you can do is multiplier overclocking. On the boards with an AMI BIOS you have to be careful. You have to mod the L6 bridges, otherwise the default remains 24X and would mean you system would try to POST at 24 x 100 (or 24 x 133). Generally this is too high an overclock at POST time.
For boards with an AMI BIOS you need to remedy this condition. You can do this by lowering the L6 bridge setting to something more reasonable. It's got to be something that your board will allow your CPU to POST. It's not too bad if your board will default to 100 Mhz FSB but can be a nuisance if it defaults at 133 Mhz FSB.
Now with a board with an AWARD BIOS, there is no real problem. These boards use the multiplier determined by the L3 bridges instead of the L6 bridges. The L6 bridges are used only to determine the maximum soft multiplier and have nothing to do with POST speed for these boards.
You can use boards with either BIOS you just need to be aware of the above info.
No nForce or nForce2 boards support soft multipliers (not yet, anyway).
Here's the only list of successfull and unsuccessful motherboards that I am aware of. I'm sure there are other boards that work. It's just that no one has compiled an authoratative list.
By the way, I gave soft multipliers a half-hearted effort. Using an Epox 8KTA3PRO (KT133A) I tried turning my Tbred into a mobile. CPUMSR didn't detect my CPU as a mobile processor so it was a No Go. My failure was probably due to the fact that I was only using the pencil mod as I was out of conductive paint.
I tried it because I was curious.
I gave up because my CPU is an unlocked Tbred and I don't really need soft multipliers.
[edited for clarity]
<b>A mind is a terrible thing</b><P ID="edit"><FONT SIZE=-1><EM>Edited by phsstpok on 10/25/04 03:47 PM.</EM></FONT></P>