Asus TX97 boards (e.g. TX97-E, plain ol' TX97, etc.) will go down to 2.0Vcore with beta BIOS 0112.
I'm currently running a K6-2+-450 from TigerDirect at 6.0x83 = 500 and doing software-based DVD decoding. Works great.
- ASUS TX-97 mobo
- 64M "old-sk00l" SDRAM (i.e. "before it was called PC66", though it's probably equivalent to PC66)
- Pioneer DVD-104S (IDE 10X drive, slot-loader)
- ATI Rage II+ PCI card, TV-out, "hardware motion compensation", but no real MPEG-2 decoding capability
- SoundBlaster 32 (ISA soundcard)
- K6-2+-450 o/c to 500 (6.0x83)
- Fresh Win98SE install
Total hardware cost, $34.99 for the K6-2+
Results: Minor skipping under WinDVD 2000, because I'd forgotten to enable DMA mode on the DVD-ROM from within W98SE device mangler.
I used the tool at http://www.simmtester.com to verify that the RAM could work at 83 MHz.
A K6-III-333 from Fry's will boot Windoze only at 360 (6.0x60) on this mobo. I have not tested software-based DVD decoding with this config, but would suspect it might also work.
Given how low-end this system is, I suspect any 430TX-based motherboard capable of running a K6-2+ (gotta be the "plus" version of the K6-2) or K6-3 mobile will have a good shot at doing software-based DVD, even with integrated video. (Did any boards of this era have integrated NTSC-out?)
The K6-2+ (128K of L2 on-die) and K6-3 mobile (256K of L2 on-die) didn't exist in 1997 - so all those FAQs about "you can't do software-only DVD without a high-end chip" don't necessarily apply.
This hack has me sufficiently intrigued that I'm gonna spend some time tomorrow seeing just how "slow" I can clock this thing and still get good playback.
Suggested torture-test for anyone else who wants to play with software DVD - the "chopper smashes into building" scene in chapter 32 of "The Matrix".