Processor question

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Piru wrote:
The original CPU is shut down completely when the accelerator's CPU is in use. The original CPU isn't used at all, not even at power on.

IIRC the A1200 expansion slot has some CPU override pins etc which the accelerator use to override the original CPU.

Is the CPU halted (i.e. sleep mode if they had such a thing 15 years ago), Or is it still drawing full current?

I've suspected that it's still on, but I've not checked the 020 temp.

What does intregue me, is how the A600 030 accellerator works since the board fits over the 68k... I would have imagined there would be conflicts :-?

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LinchpiN wrote:
I always wondered that too, you'd think the system would either see nothing or both...

Thats why im not an Electronics engineer...

Well, it's been my assumption that the clip over socket holds the 68k rest pin high so the 68k is in a permanent reset... but then the 030 would not be able to see any reset signals from the motherboard (does it need to?) :-?

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Zac67 wrote:
You can't keep _RST high as the driver pulling it down would be overstressed or even burn out.
I guess they use/mimic some bus request/bus grant stuff to get the 68k out. The '030 requests the bus and just never gives it back. (In contrast to other architectures the M68k itself is fully DMA capable since it is possible to arbitrate for the bus.)

I wasn't aware the 68000 bus was as sophisticated as that, I'll have to check my datasheets :-)

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Zac67 wrote:
W/o large caches there's not much point in putting two CPUs on the same bus, they'd be waiting for RAM access most of the time. An '040/060 dual system with (separate) cache(s) would be something different though. Makes me think of Dave's Gemini research, which had never been able to run AmigaOS afaik.

I think he stated that it would run a "special" version of exec.