5x0(c) CPU card differences

[Franklinstein]

I pulled apart a 520 the other day. Indeed there are many clock crystals in the system: at least four on the logic board for various subsystems and one on the processor card to clock the processor/processor bus. The processor card crystal runs at 1/2 bus speed, so it's 12.5MHz in my 25MHz-bus example. So changing bus speed to 33MHz would need a 16.7MHz crystal, or to 40MHz a 20MHz crystal. Overclocking is not a good idea, as mentioned, because these things run warm as it is and there's no room for additional cooling (unless perhaps the modem parts are removed and maybe a tiny fan could be fitted to the phone jack port).

I don't think there's a difference between the other 5x0 series and the 550's ROM; I think it's just that the QFP 68040 is apparently NLA from new (and as we discovered the modern 68040V is a low-voltage FPU-less design) so I have no idea where you'd get one.

 

[Trash80toHP_Mini]

Quite a few years ago some full 040s in QFP showed up as available and some of the gang bought them, looking to make laptops compatible with A/UX. Don't recall how that turned out, anyone?

 

[Trash80toHP_Mini]

I can tell you from the benchmarks I have done, a blackbird running a full 68040 is indeed equivalent to a Quadra. The only 68k system that really beat the crap out of it was the 840AV, but, that's to be expected.

Interesting, I wouldn't think that would be the case as everything is on a 16bit system bus other than CPU/RAM/ROM. I wonder if the Quadras you tested were running only 8bit video like the Blackbird they'd have done better against it?