jessenator
Well-known member
I had some questions about oscillator swapping (overclocking) the Centris 650 (modified gestalt ID via on-board resistor), Quadra 650 and Quadra 800 boards. Namely some questions regarding the 'limiting factors' mentioned.
So according to Marc on the archived clock chipping page:
I've thought about emailing Marc directly to ask these questions, but figured I'd ask here first to see if anyone has attempted this and how they got on.
Firstly, has anyone run their Wombat-based Mac at or above 44 Mhz? Or were there any sort of system instabilities they ran into which forced settle on 42 or 40 MHz?
Secondly, were these overclocks done with the stock CPU—be it 25 or 33 Mhz? Or were they done with a late-mask, fully-qualified MC68040, be it 25, 33, or 40 Mhz?
I'm curious if the limiting factors are indeed board/component-related, or if there were problems with the original overclocks when attempted on the XC, un-qualified silicon present in 040 Macs at the time. I've heard whispers of the new-make Turbo040/Carrera 040 upgrades able to run at 50 Mhz with proper silicon, but I think those posts were wiped out. I could be wrong. Interesting to note that the 840av—though a different board—can go to 48 Mhz. I would definitely be attempting this with my later-mask 40 Mhz CPUs.
I mean, I'm sure it's diminishing returns after a certain point, but I'm curious all the same.
So according to Marc on the archived clock chipping page:
And then on the current Output Enablers chart of upgrades:When you run these machines around 40 MHz, video problems seem to be the limiting factor.
Quadra 650 | 44 Mhz ---- Quadra 800 | 42 Mhz
I've thought about emailing Marc directly to ask these questions, but figured I'd ask here first to see if anyone has attempted this and how they got on.
Firstly, has anyone run their Wombat-based Mac at or above 44 Mhz? Or were there any sort of system instabilities they ran into which forced settle on 42 or 40 MHz?
Secondly, were these overclocks done with the stock CPU—be it 25 or 33 Mhz? Or were they done with a late-mask, fully-qualified MC68040, be it 25, 33, or 40 Mhz?
I'm curious if the limiting factors are indeed board/component-related, or if there were problems with the original overclocks when attempted on the XC, un-qualified silicon present in 040 Macs at the time. I've heard whispers of the new-make Turbo040/Carrera 040 upgrades able to run at 50 Mhz with proper silicon, but I think those posts were wiped out. I could be wrong. Interesting to note that the 840av—though a different board—can go to 48 Mhz. I would definitely be attempting this with my later-mask 40 Mhz CPUs.
I mean, I'm sure it's diminishing returns after a certain point, but I'm curious all the same.