PCMCIA friendlyness

[Secret Vampire]

Does anyone here know how PCMCIA friendly memory expansions work with A1200 systems? I know it's not a problem for <=4MB expansions, because that leaves 4MB of the primary expansion space free for other stuff, but how the 8MB ones are implemented is puzzling me. Obviously for an accelerator you can just put the RAM in 32 bit address space, but for a straightforward RAM expansion?
I know that there is a small amount of additional autoconfig space at E90000-EFFFFF, and the slow RAM space, so I'm assuming that such a card either forces the PCMCIA controller to put any i/o cards in the extra autoconfig space (wouldn't really work for SRAM, but then, if you have 8MB already, why would you need it?) or places some of its RAM into the slow space to leave a gap in the normal expansion space. I'm assuming the former is more likely, but I've never used a PCMCIA friendly 8MB board, it might show up as 6.5MB fast, and 1.5MB other, I know DKBs A1200 ram board did it that way, but only gave 5.5MB if configured as such. So the question is, if it does work by moving the location of the PCMCIA cards, how would you go about doing it?

[utri007]

PCMCIA friendly accelerator have allways MMU = memory managemen unit, MMU maps own address space to accelerator's memory

[alexh]

@utri007

Secret Vampire is talking about PCMCIA friendly RAM expansions not accelerators.

PCMCIA friendly accelerators map their fastram in the 32-bit address space far away from where the PCMCIA appears. They DONT use MMU's. They dont have them! They use configurable address decoders usually implemented in a CPLD.

@Secret Vampire

I am almost certain any PCMCIA friendly RAM card would have to move it's the RAM rather than move the PCMCIA port (which I think is impossible.) It is very interesting. The A1200 24-bit Address map is fairly full.

[Npl]

usually the accelerators will use an area above 100 0000 for their RAM. In short, put it above the 24bit Memory-space in which the PCMCIA resides. That ofcourse requires a CPU that has 32 bit adresspace, like the non-ec-68020 and above.
The MMU has nothing to do with the mapping, its hardware on the card that maps the RAM to its effective address.

[Npl]

Originally Posted by alexh

ny PCMCIA friendly RAM card would have to move it's the RAM rather than move the PCMCIA port (which I think is impossible.) It is very interesting. The A1200 24-bit Address map is fairly full.

Its not impossible if the Card contains a CPU (it could catch and remap any move to the PCMCIA-Area as it sits between CPU and A1200), but messy and unecessary if you have a few GB of free Adresspace.

[alexh]

Originally Posted by Npl

Its not impossible if the Card contains a CPU

Eh? But the whole point of this thread is that they are just RAM cards i.e. no CPU.

[Npl]

Originally Posted by alexh

Eh? But the whole point of this thread is that they are just RAM cards i.e. no CPU.

Oops, sorry.
Well, if someone has such a board it would be interesting to see what showconfig would report, dont think they would fragment 8MB over all holes in the Memory-Map. Maybe they disable PCMCIA during bootup , let the ROM configure them in the 8MB Autoconf space, then enable PCMCIA and let the ROM configure it in whatever is left (secondary Autoconf-space) ?