Mega Midget Racer in 68000 mode doesn't work with A590 SCSI controller?

[AmmoJammo]

is this a known/common fault?

took me a while to realise what was going on.

seems running in 68030 mode (at 33Mhz) it's perfectly fine.

but if I connect the jumper on the board, or use the software switch and run it at 7Mhz, I get varying errors when it trys to boot, either from the HDD, or FDD...

Unplug the A590, and it seems to be fine?

[Azryl]

Most CPU socket accelerators fail due to DMA bus to memory problems. Once the onboard 680x0 chip forces itself dominant on the bus you get DMA to Fast RAM issues.

The problem is memory no longer accessible to the motherboard but now addressed to your socketed accelerator.

It breaks the DMA, ie Direct Memory Access.

PIO modes can sometimes work with socketed accelerators, PAMC and Adspeed etc

Az

[AmmoJammo]

what fast ram?
the ram in the A590 is disabled, I was using 8meg under the 68000, but it needs software to be added anyway.

do you think removing the ram from the A590 would make a difference?

[AmmoJammo]

Also, the A590 has the AM33c93A SCSI controller, as well as AM33c93A Version 7.0 of the roms.

[AmmoJammo]

disabled "Autoboot ROM" (turned switch 1 off at the back of the A590)

boots workbench 1.3 from floppy in 68000 mode no worries!

so, what now?

try the old SCSI roms?

[VingtTrois]

Is it possible for you to test the A590 with another AMIGA?

[AmmoJammo]

Is it possible for you to test the A590 with another AMIGA?

with the mega midget racer?

[VingtTrois]

With and without!

[AmmoJammo]

With and without!

the MMR works fine when using the 68030 processor, and A590.

the A590 works fine when using a 68000/68010 processor plugged directly into the A500 motherboard.

the only issue seems to be when trying to use the MMR in 68000 mode, with the A590.

[Azryl]

the MMR works fine when using the 68030 processor, and A590.

If I remember the a500 DMA channels correctly some are from gary, some from denise and the remainder from Agnus. Depends which DMA channels are used by the a590 to bring data from the drive into the motherboard then ram via the 86pin side expansion bus.

the A590 works fine when using a 68000/68010 processor plugged directly into the A500 motherboard.

Because this is the standard mode for the 86pin side expansion, all commodore branded expansions should work with this configuration of hardware.

the only issue seems to be when trying to use the MMR in 68000 mode, with the A590.

The 86pin side expansion is a near pass thru of the 68pin cpu socket, but now you will have some extra glue logic involved when you use the fallback mode of the MMR, something unexpected is getting in the way. You will need to research the MMR some more, or try to place the a590 into a different mode of data transfer.

As I said earlier, cpu accelerators that use PIO mode transfers from 86pin expansion bus work, Mtec i68020 + Mtec megabody etc.

If you remove the cpu memory adapter and try the onboard a590 2meg fast ram maybe the ram config will allow the MMR fallback mode.

Az

[AmmoJammo]

I get two errors?

with Kickstart 1.3 enabled:
http://img193.imageshack.us/img193/8487/20120821174859.jpg
http://img208.imageshack.us/img208/9901/20120821193216.jpg

and then with Kickstart 3.1?
http://img89.imageshack.us/img89/3806/20120821193318xq.jpg
http://img211.imageshack.us/img211/8562/20120821193346.jpg

[Merc]

@AmmoJammo:  when you are in 68k mode is your fast ram on the MMR (assuming there is some) still available?  That is probably the problem, I had similar problems with my A590 when I had an mtec 68020 accelerator with fast ram...  the problem seemed to be that the fast ram was mapped into DMA space or flagged as DMA capable which caused the A590 to try to use it for DMA, which doesn't work.

The best I could manage until I went with a different HD controller was to boot from floppy and mount the HD manually via a mountlist and then boot the HD.  

I guess when in 030 mode the ram is mapped out of DMA space.

Disclaimer:  It's been many years since I had this gear so I might be misremembering some details!

I guess when in

[psxphill]

If I remember the a500 DMA channels correctly some are from gary, some from denise and the remainder from Agnus. Depends which DMA channels are used by the a590 to bring data from the drive into the motherboard then ram via the 86pin side expansion bus.

The chipset DMA channels are controlled by agnus, denise & paula just gets/supplies the data. These can only access chip ram.
 
DMA using the expansion slot are different. They are like Zorro bus masters, they control their own DMA channels and just drive the bus using an arbitration scheme.

[AmmoJammo]

@AmmoJammo:  when you are in 68k mode is your fast ram on the MMR (assuming there is some) still available?

nope, not available.

all the accelerator has is 512k of super dooper fast ram.
but it's not accessible in 68000 mode, and from memory, fall back mode with the A590 didn't work, even when there was no ram on the accelerator.

[number6]

@thread

In case no one mentioned this:

The addendum of the mega-midget racer manual indicates that for use with a hard disk system and FFS (may apply to other file systems, but manual was written during the heyday of FFS), you must change the mask.

Oh, and the reason the mega-midget racer was top of the line probably had more to do with the designer than the company. Heh.

Steven L. Kelsey - Hardware and Principal Engineer -- Computer System Associates (CSA)

He just happened to design the Macrosystems products too...

#6