Posted Sat Apr 01, 2023 9:52 pm
To be clear, it is impossible to have more than 512KB of useable chip RAM on the Amiga 1000.
Yes, Kickstart will see any RAM in the $000000-$1FFFFF range as "chip RAM" but Skinny Agnus is only able to access 512KB, period. No ifs, ands or buts. Since Agnus generates the DMA, this means Denise cannot and Paula cannot either. There is 512KB of real chip RAM in that and 1.5MB of "slow fast" in the normal chip RAM region. This could cause compatibility issues if AmigaOS wrongly assumes all of this to be useable and attempts to put any bitplanes, audio samples, or what not into the extra 1.5MB of RAM.
This is based on a fairly well documented hack published in a magazine back in the day. You stacked RAM chips to hijack most of the signals and refresh but then rerouted the missing, higher address signals to use those chips. You got a 1MB system with them double stacked, and clearly, you can go to 2MB with four.
But it is NOT real chip RAM.
The CPU doubler looks like it's based on the work done on the Atari (I forget the name of it off the top of my head). It doesn't quite double the speed since some operations cannot complete any faster. I think it was closer to 50-60% faster, which I guess is still a nice boost.