Originally Posted by demolition
I think the most compatible solution would be a 44pin IDE connector. A CF adapter to go on this is widely available and costs almost nothing. The user would then have the choice to attach adapters for CF, SD etc. or use DOMs directly with 44pin interface. You are right that probably not many would use mechanical drives on it.
The initial concept with stacked PCBs already had a compromise with it's 40-pin IDE: I don't want to offer 44-pin, as that one carries power that would overload the PSU of 90% of the A500s out there.
Experience from clockport expansions has shown that the vast majority of customers either doesn't read manuals, or mis-interprets it. A Plain "don't use with harddrives" note doesn't do the trick; people would try it anyway.
A key feature of the ACA500 shall be that it's compatible with *any* A500 that's out there, and that includes the units with 2.5A heavy-transformer-type PSU. Most of the laptop harddrives require up to 1A on startup and easily 0.5A in normal operation. A CF card takes an order of magnitude less than that. That's a no-brainer.
I do need the very early execution of $f0 ROMs in order to boot from CF even under Kick1.2. Autoconfig ROM is not an option (and it would break compatibility with even more A1200 accelerators, because there is no config in/out lines on the 150-pin slot). The 2M Fastmem is available to the A1200 accelerator through Z2 mem space, just not using the autoconfig mechanism in order not to collide with possible autoconfig use on the A1200 accel. Your assumption that "only adapter+IDE" makes it easier is not in line with reality; that would have no means of dealing with the Kick1.2 issue.