Has anyone tried overclocking a "Mach5" 604e found in the later 8600/9600's? xlr8yourmac shows how to change multipliers by swapping resistors. Mike was able to get his 350 up to 400 with no problems. Settings are shown for up to 450MHz. I'm wondering if I could push a 350 that high with some additional cooling. 
Overclocking Mach5 604e
January 23, 2005 - 3:02pm
#1
Overclocking Mach5 604e
doubtful
still worth a try
If you were going to try anyway, why did you ask our opinion?
I just did it about 5. min ago to a 8600 and it works fine!! it was a 250MHz, and i pushed it up to 400MHZ!! NO ADDED COOLING!!
How'd ya do it?
Got any screen pics of proc speed?
Is it stable?
I hope you'll forgive me if I'm skeptical. Those cards just weren't good overclockers. On XLR8's website, it would seem you should be thankful if you got a stable 50 MHz extra.
You said it was a 250Mhz and you brought it up to 400Mhz. you are I assume posting about a kansas logicboard in a 8600 and changing the clock speed on the CPU by changing or moving the resistor. Did you just resolder the resistor at 400Mhz on the CPU or do you have to use more than one??. You have my courisity up as I have about 8 or 10 of the mach5s set at 300Mhz and it would be nice to know if all you had to do was resolder a resistor to get a higher clock speed
I'm now skeptical, too.
I thought this post was by the original poster, but its a different ID, from a poster who's been here less than a day and this is their only post. Suspicious...
Although, I know little about overclocking in general... and I have at least 3 604e machines. It would be nice if this kind of overclocking could be done safely, and keep the machine relatively stable. I'd love to see a 400MHz ANS. It would almost make it relavant again.
I can never find anything on XLR8s website... do you mind posting a link the page you're referring to?
...to XLR8yourmac's 604 page with o/c info:
http://www.xlr8yourmac.com/tips/mach5info.html
[Edited first paragraph]
Just checking, did you fiddle with the resistor jumpers at R11-14 to R19-22 or did you move R252 to R249 (image below)?
http://www.xlr8yourmac.com/tips/mach5mod/SpeedID2.JPG
If you did the prior, good. If you did the later, No Go. That jumper does nothing to the actual speed of the card. A resistor is only placed there during assembly as a quick identifier, it does nothing. Check your system profiler for actual speed.
I have a couple of those cards. One I went from 300 to 350Mhz and was was stable. Another of the same speed was not. I doubt going from 250 to 400Mhz would work, UNLESS they needed some 250's to make quota and they only had some 350-400Mhz CPU's in stock. I've seen that before with G4 daughter cards, an on-purpose underclocking to meet a quota. I'm sure it probably applies to many components in the electronics industry.
Another scenario I've seen are batches of CPU's that fail at their intended Mhz rating but pass at the next lower multiplier. Thus they are sold/used at the lower Mhz speed setting. Perfectly normal practice. For general usage, they would probably run indefinitely at their intended speed but manufacturers seem to put more fudge-factor into said items for a more stable product, less re-working/liability/etc. which also equals lost dollars in the end.
But I'm so broke I'll just throw in my 2 cents.
-Dk