WarpEngine 68060 @80mhz!

[NovaCoder]

OK, episode #3 of A3660 overclocking is completed!

Once again, many thanks to SuperCosmos for the rev. 6 060 (and for his patience with my stupid mistake delaying this update for another 2 months)

The custom oscillator I made used a dual frequency crystal so changing the frequency was quite easy. The more complex part of this episode was the CLK D4 GAL designed as the solution to keep SDMAC happy.

The CLK D4 GAL switches the mobo to a 1/4x clock during DMA so SDMAC is supplied with clock speed it can handle and the mobo runs at the 1/2x clock speed when the CPU masters the bus. See attached images.

This also works quite well with the 040 but I was really saving it for this episode!

Higher clock speeds are still possible but I will have to source some oscillators or crystals for the next episode.

Nice to see such speed out of a Classic machine, now go run something that needs such speed like...

 

[SpeedGeek]

OK, episode #4 of A3660 overclocking is completed!

Unfortunately, SysSpeed becomes less accurate at higher clock speeds so I have included a Scout result as well.

The CLK_D4 GAL signal BGACK_040 is now connected to VCC. This always runs the mobo at the 1/4x clock speed. Also, more A3000 mobo and CLK90 timing mods were made to keep the following clocks skew compensated and stable:

68060 CPU = 80MHz
A3640 logic = 40MHz*
A3000 mobo = 20MHz

Note: Considering that the A3000 is a timing intolerant beast overclocking the mobo to 40MHz was not a practical consideration here.

*A3640 state machine mod required