After much wailing and knashing of teeth, I have come to the conclusion that the 300MHz boot-up
limit (or thereabouts) for the K6-II+ / K6-III+ chips is a limitation of the BIOS on "unknown" chips.
I have had a (recognized) K6-III booting at up to 450MHz (100 x 4.5) for several months using
the Maxim power board without difficulty, and was interested in using the K6-II+ to try for
a higher speed without getting into cooling problems. I have been pulling hair for several
days because I had all the voltages right, the BIOS was seated well, but the screen was coming
up blank and staying blank (I was jumpered for 400MHz, my usual K6-III boot speed). Power
wasn't the problem; the maxim supply has more than enough amps at 2v. Reset wasn't a problem
either; I already put a capacitor and resistor across the reset button when I made the 450MHz
system mods (the computer was coming out of reset before it was stable, and required a manual
re-reset at power-on - this was no longer the problem)
What tipped me off was that _the power button would turn the system off_. Normally, when
things are in a no-boot situation (bad BIOS, bad CPU), the power button will turn the iOpener
on, but will not turn it back off.
When I tried to boot the K6-x+ at 350MHz or above, I would get a blank screen but a working
on/off button, and could turn the unit off again.
This observation also explains why people can boot at 300 but then jump up to 600MHz and still
be stable...their problem is the BIOS rather than lack of amperage.
I am using the V5BIOS_patched.bin from f r e e d r i v e . c o m (iopener / iopener). If
anyone can boot a K6-x+ (with 100MHz front-end) above 300MHz, please post which BIOS version
you are using. This works on both V1 and V3 iOpeners.
If no-one has a BIOS allowing high-speed boots, does anyone have any ideas how we could splice
the K6-3 timings into the "-MMX" (which is how my system identifies the CPU) table in the BIOS,
or alternatively, if we could replace a low-end CPU ID and timings in the table with the K6x+
identifier and the K6-3 timings?