@sharpie
Some basic terminology that is banded around..
OCS/ECS/AGA refer to different versions (in chronological order) of the chipset that gave the amiga it's original graphical and sound capabilities. AGA was the largest improvement, offering greater speed and more colourful displays.
This chipset share a block of memory with the processor, called 'Chip Ram'. Only the chipset or the processor can access this memory at any given instant. On the original amiga systems, which used a motorola 68000 processor, this set up was ideal, since the 68000 could only access the memory 50% of the time anyway (slight oversimplification but generally true) - usually every even clock cycle. The custom chips therefore were able to use every odd clock cycle.
So the design allowed the 68000 to run virtually unimpeeded whilst the chipset did its magic in parallel.
The problem with this design is when you get faster CPU's such as the 68020 and above. These can access memory every cycle and are forced to wait when the chipset is accessing the memory.
Even the 68000 itself can be slowed down when there is a lot of chipset activity using the Chip Ram (hence needing more than 50% of the available time).
So, the designers also came up with a solution for that too - an area of memory useable by the CPU but off limits to the chipset. This memory is generally known as 'Fast RAM'.
On the original 68000, the presence of fast ram made only a small impact on the speed (apart from in a few rare cases where both CPU and chipset were very busy at the same time).
However, on systems using faster CPUs such as the 68020 and above, the impact of fast ram is rather more profound.
A bare A1200 which uses the AGA chipset and a 14MHz 68020 CPU typically doubles in speed when you add some Fast RAM (usually as an expansion card that fits in the trapdoor of the case).
For CPU expansions carrying a faster 68020, or 68030,40 or 60, Fast RAM is a must. My 68040 actually runs *slower* than the bare A1200 if the fast ram is removed :lol:
