Coldfire AGAIN

[A6000]

bloodline wrote:
Well, the V4 and V5 cores, with their separate supervisor stack do seem to have what it takes to emulate the 68000 (not sure about the data width issues though)... but the instruction traps which will be required are very expensive in terms of CPU cycles... I really do think we are looking at a massive penalty with the coldfire.

As I understand it, the coldfire is cheap, that is really the only thing it has going for it.
The amiga is a multitasking computer, so why not use 2 coldfires, running separate tasks, while one chip is trapping and emulating code, the other coldfire continues running it's task, hiding the speed penalty that emulation brings.
A few extentions to kickstart (in ram) will enable the OS to use 2 processors simultaneously.

[A6000]

biggun wrote:
A MMU adds overhead to the Chip.
Motorola 68060 chip with FPU and MMU was advertised with 60 MHz clockrate. The same CPU without FPU and MMU was running with 75 MHZ.

A MMU will add overhead and latency.
The Latency can be hidden by creating a more complex address generation pipeline and by using on chip cache(to cache to MMU tables).

Please mind that even the most simplest MMU with just one Bit per page to indicate access allowed, will need an MMU-table of 32KB.
Creating a MMU with a on chip cache and a dynamic reloading of MMU table missed is complex.
Putting the whole MMU table on chip is a simpler design but it would eat 32K on chip cache memory.

The MMU on the chip is a lot of overheat.
There is a good reason that no one does a MMU on blitter!

The presence of an FPU was the reason why the full '060 could not officially run at 75mhz, some rev6 '060s can run at 100mhz.

leaving out the MMU was an economic decision.

The benefits of an MMU, like memory protection, outweigh the speed penalty. even though the amigaOS is not suited to memory protection, an MMU IS still useful as proven by ENFORCER.

[A6000]

If coldfire could be made to run 68k code without error, then wouldn't elbox have done it by now?, they have had the dragon coldfire accelerator in "development" for at least 4 years now, I think only biggun really believes coldfire can work.