Some lessons learned from my recent A2000 rebuild

[Matt_H]

You may have seen my thread about the A2000 fire button problem, and the lesson there is to try the most damn obvious thing first. Could have saved a lot of headache if I'd just plugged in a damn joystick! Ugh.

Other observations:

The Algor Pro and One-Stop Music Shop do not play nice together. Could get the machine to boot maybe 1 out of 30 times with both of them plugged in, but no problem whatsoever with just one of them. With both of them, the machine would either hang on the Algor bootloader (with Flash empty) or immediately afterwards. Since this machine is to be a music workstation, I opted for the One-Stop, but it would be nice to get them both working...

The A2091 driver will use whatever memory has the highest priority. In my case, that's the non-DMA memory on the 2632 board, leading to horrendously slow speeds - even with the full 2MB of RAM on the A2091 itself. Solution? Reduced the priority of the 2632 RAM below that of the native Zorro II Fast RAM. Sure, that'll probably reduce speeds on other RAM operations, but the 15-fold increase in drive speed is worth it. The numerous speedup patches on Aminet seem to be intended for a 4000/040, so I haven't tried those yet.

More to come as I think of it...

[Matt_H]

On the other hand, I never knew anything about changing memory priority.  How then heck do you even do that?

The 2632 is doubly annoying because it doesn't autoconfig. It has its own addmem tool which has a few extra options, one of which is adjusting the memory priority.

For other cases, there's ChangeMemPri. Worked great on my CS Mk3 a number of years ago (wanted to have the system use motherboard RAM first in order to have a larger free block  on the accelerator for Mac emulation - back in the days when I had a mere 32MB onboard).

[Matt_H]

Everything will you highest priority RAM first. Have you configured the mask value correctly?

Probably not. Do you know what it should be? This might be a better workaround.

[Matt_H]

No, but it's not too hard to figure out. If the A2091 memory autoconfigs to $200000 to $3FFFFF and the A2630 (non-DMAable) RAM goes to somewhere beyond that (doesn't really matter if it's $600000, $20000000 or whatever) you can simply use a mask of $3FFFFC. (The two least significant bits set to 0 make sure a buffer is longword aligned, speeding up the '030's access somewhat.).

In a nutshell, you use the highest address DMA works at and set the lowest nibble to $C: $3FFFFC for a 2 Meg RAM board and some below $FFFFFF 32-bit RAM, or $9FFFFC to use any Z2 RAM but no extended memory, or even $FFFFFC if you've got Ranger or slowfast mem.

However, if the A2630 RAM configures before (=below) the A2091 RAM we'll need to get more creative. Post the memory locations and we can work it out.

btw: the A2630 RAM should autoconfig (J303 open)

Thanks for the help. Looks like the RAM on the 2091 and 2630 autoconfigs as a contiguous block from $200000 to $7FFFFF, but the 2091 seems to start at $600000 according to ShowConfig.