As an ex programmer/hacker on the Amiga (I use programmer loosely
)
Adding fast ram on the Amiga 500 would not double its speed. (sort of)
The chip ram in the A500 is not the bottleneck on a 7.14mhz 16bit cpu .
The issue of speed was when any of the custom chipset was accessing Chip ram the CPU was in a wait state and had to wait its turn to access the ram.
Really stupid of commodore to do this and adding 512k of fast ram would in effect double the speed as playing sound in 4 channels, copper effects, blitting, Accessing ROM and even just displaying a graphics screen all took time away from the cpu (Like HAM).
HAM was a work load for the chip set not CPU, HAM is a standard 32 colour picture (OCS) but every scan line (200/256 in lores 400,512 laced) the palette is changed, so HAM is a cheat 4096 colours(OCS) on screen but not per line, this caused the chip set to change the palette every scan line and while this was going on the CPU had to just sit there and wait.
Adding fast-ram would free up the CPU running the code in fast-ram at the same time the Chip set ran its own routines in Chip-ram,
Again another disadvantage of Fast-ram is that only code and data can sit in fast-ram, the cutom chip set cannot address fast ram again another sucky idea from commodore,
I loved programming the Amiga and the custom chip set and library routines in ROM made it so easy.
