Overclocking Apollo 1240/40 to 50MHz?

[tomekm]

I am looking for info on the following topic:
Is the Apollo 1240 able to drive 68040rc40 at 50MHz i f I replace the oscillator with 100MHz one? I know the 040 itself should handle it. Especially if my one does not generate much heat (Pentium 1 and little fan driven by thermistor is much more than enough).

Does anyone know if it works and does anyone have 100MHz oscillator to sell?

[tomekm]

ok, let`s verify some things:

-afaik the fastest version of 040 is 50MHz.

-My 040 is the RC revision.

-My 040 DOES GENERATE MUCH HEAT, it is cooled by Socket7 lowprofile radiator and 486 fan, driven by a thermistor. It is far more than enough. I remember one time I forgot to give the voltage to fan. The computer hung up after 5 hours of hard work (DigiBoosterPro)...

-My A1200 is fitted in BIG tower.

-My PSU is 250W.

-The fan voltage is not taken from Apollo, instead directly  from PSU.

Seems that overclocking should be possible, but I have no oscillator to check, and don`t want to buy one until I`m sure it`ll work because they`re too expensive (and unavailable in my city).

 

[tomekm]

No, the fastest version of the '040 is 40Mhz.  Some Mac expansions were shown as beiing 50Mhz becuase the 25Mhz 68040 needs a 50Mhz oscillator as it's timed to cycle on every second oscillator pulse.  If you check your CPU you will find that an 80Mhz oscillator is fitted, thus giving 40Mhz chip speed.

i know that 040 uses every second cycle, altrough for I/O operations only. The processor`s arithm core runs at full speed (in my case 80MHz). That`s the reason why there are 50MHz 040 in Macs. I know it. But also I`ve seen a table of benchmark results taken from some web page which showed: 040/25, 040/33, 040/40 and 040/50. So it means that there was 50Mhz version. Also: i`ve seen old 040/25 running at 40Mhz, so  i see no reason to run 040/40 at 50.

[tomekm]

OK, thank you all... I`ve got blizzardppc (which is dead now... but i`ll try to recover it.

[tomekm]

OK, thank you all... I`ve got blizzardppc (which is dead now... but i`ll try to recover it.