Which affects speed more? Processor or RAM?

[matthey]

Processor! The processor has caches that are extremely fast memory. Most Amiga programs are small and a good portion of the programs can stay in the cache on later 68k processors. The memory speed is still important though. Some programs will slow down a lot with slow memory.

[matthey]

Starting with an 68040 (8k cache) you start to notice the performance benefit of the cache memory. Processors nowadays wouldn't be any faster if they didn't have very fast and adequately sized level 1 cache memory. Level 2 cache memory larger, but slower only adds about 15% more speed.

Bingo! Even the C= A3640 performed reasonably well using only motherboard memory because of the cache and small Amiga programs. It generally outperformed a 50MHz 68030 with faster memory and 2x the processor speed. It had a lot to do with the cache. It is more important to have some fast ram instead of chip ram though. The CPU can be slowed to as much as 1/2 speed without fast ram as the custom chips steal CPU cycles.

[matthey]

A1200 (2MB Chip, No FastRAM)
1092 Dhrystones
1.13 MIPS

A1200 (2MB Chip, 2MB PCMCIA SRAM)
840 Dhrystones
0.87 MIPS

Some RAM makes the Amiga perform faster, other RAM can slow it down.

That is odd and rare. That must be some slow SRAM. The OS probably gives the SRAM a higher priority than chip ram as normal but it must be slower. You need ChipMemFirst for this 1200 . Lot's of memory on the Amiga can actually be slower after it's fragmented unless running TLSF mem or similar. There is a longer memory list to transverse.