So-called "slow RAM" is the same speed as chip RAM but can't be accessed by the custom chips.
The hardware reference manual 3rd edition calls it slow.
http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node00D3.htmlFat agnus was changed to support 1024k of dram, but they didn't change the address register widths in the dma engine (probably to save time/cost). I believe it was a way of trying to stop Jay Miner going on about the ranger prototype, where the additional memory 1mb ram was actually fast (I'm not exactly sure where it was mapped). In the Amiga 3000 memory map they label the 512k area @ c00000 as Ranger RAM.
The 2630 that shipped in the 2500/30 is a bizarre design in that it uses 32-bit RAM that is mapped into the 16-bit address space.
It's not the bizarre. RAM was still expensive and having it possible to DMA into your 32bit RAM from another ZorroII card is pretty useful. I don't think 32bit memory moved out of the 24bit address space until the A3000 brought Zorro III.
