Silly question: Change CPU speed?

[dhoelzer]

I'm sure this is a very silly question, but I'm still curious...

I've built some small scale projects using FPGAs... Generally dual ported RAM video display adapters for some retro hardware.. Nothing nearly as complicated as even a simple CPU.

Still, I'm wondering.. How difficulty would it be to modify the speed of the 68020 core, or would that just throw the timing of everything else off?

Thanks

[Sorgelig]

CPU speed can be lowered by delaying memory reply signal.
Core has 2 CPUs inside, so for cycle accuracy for old games/demos there is 68000 CPU.
68020 is not cycle accurate, so lowering down the speed won't bring a cycle accuracy, so you won't get cycle accurate A1200 for example. Some instructions will be slow, some will be fast. Thus 68020 is made to be as fast as possible to cope with high-end Amigas.
Fortunately later apps/games don't assume specific CPU speed.

[dhoelzer]

I was actually hoping to raise the speed... but it sounds like it's already maxxed out! My desire is primarily related to the speed of the display at 720, but if the RTG is merged that should naturally improve the rendering on higher resolution/color depth displays.

Thanks

[NightShadowPT]

Believing in the information from SysInfo, the 68020 is already operating @99Mhz.

To significantly improve the performance from here, someone will need to make na FPGA implementation of a 68030, 68040 or 68060.

Until then, I guess this performance is as good as we are going to get. (and let's be honest, it is already amazing)

[kolla]

Keep in mind that “the 68020” isn’t really a 68020 at all, it can be faster on some things and slower on other, compared to real 68020. Tobiflex wrote some time ago that he intends to make a new 68k core, one that is 32bit from the start, and not “mostly 16bit” like tg68 is.