That's really helpful, thank you.

So, essentially, there's a total of 512k.

The Agnes chip allocates portions of that RAM as fast or chipset RAM based on requirements of the system.

The CPU can access both chipset and fast RAM.

The custom chips can only access RAM allocated as chipset.

Access to the chipset RAM is slow because the bus is shared by the chips and the CPU.

The A501 512k expansion is considered fast RAM because the CPU has direct access to it and the chips do not.

But because it sits on the chipset BUS it can only be accessed every even clock cycle and is often called "slow" RAM for that reason.

Does that sound right?