Is the on-board CPU used at all in accelerated Amigas?

[AmigaMance]

When an accelerator is plugged in the CPU slot of an Amiga 1200, its CPU takes over the 68020 of the motherboard. Everyone knows this. What i'm curious to know is whether the 68020 is used at the initialization phase and if the Amiga will be able to boot even if it is damaged.

[psxphill]

When an accelerator is plugged in the CPU slot of an Amiga 1200, its CPU takes over the 68020 of the motherboard. Everyone knows this. What i'm curious to know is whether the 68020 is used at the initialization phase and if the Amiga will be able to boot even if it is damaged.

Possibly.
 
On the original german A2000 you had to take out the main CPU if you added an accelerator as there was no way to disable it.
 
Missing is probably ok, if it's damaged then it might create bus activity that stops the accelerator from working.

[Oli_hd]

No, the onboard CPU is kicked off the computer bus by the accelerator and it never asks to be let back on. (because its not told too)

[TheGoose]

No, the onboard CPU is kicked off the computer bus by the accelerator and it never asks to be let back on. (because its not told too)

Damn kicked off the bus! Not let back on. Low.

[Daedalus]

Yup, as the others have said, the 68020 is totally disabled and doesn't execute a single instruction of the OS boot, but it depends on the nature of the damage. If it sits there and behaves like a normal disabled CPU, then it should be fine. It's quite possible though that it'll try to hold some lines low or high or something like that, meaning that the bus itself is jammed with no way for the accelerator CPU to use it.

[haywirepc]

It would have been cool if you could still use both cpu's, like somehow route background tasks to the older processor.

Steven

[Daedalus]

Yeah - get that handling input.device, timers and other low-level stuff like that would be great... Oh well :-)

[coldfish]

Yeah, I always felt a bit miffed with my A1200 68030@40 knowing there was a 020 with a few MIPS right there on the motherboard doing nothing.

bummer.

[tone007]

It'll still make some heat, if that makes you feel any better!

[coldfish]

In that case, all is forgiven.

[bloodline]

While an Asymetric Multiprocessor System based on using the 020 and the accelerator CPU probably wouldn't be very useful for any real system... You would need to target the 020 specifically, and then only a few Amiga's would have them, different configs etc... But from technical point of view, I would guess you could do it providing the accelerator board was designed to share the bus, and you ran some custom software on the 020 etc...

[ElPolloDiabl]

Multiprocessing was a big deal back then. Plus wouldn't you need a capable OS?

[abbub]

On the A2000 with a 2630 you can hold down the mouse button and boot off of the original 68000, in case you run into softwares that can handles the awesome power of the 68030.