I can't remember where I found it, but it's in the kickstart 3.1 change log.
Here is the part for expansion library:
expansion 40.2
- New - A1200 specific build that can detect CPU Slot RAM ($08000000)
if you have a 32-bit addressing CPU installed. The CPU slot area
is 128meg in size (just like the A3000) but has the addition of
a wrap check at each 1meg of space in the CPU address space to make
low-cost RAM expansion possible without jumpers. (It is now possible
to get 128Meg SIMMs so a single SIMM on a CPU card could make a
128Meg of FAST RAM system )
The reason that this has to be A1200 specific (at least for now)
is that the behavior of the existing A500/A2000 CPU cards with
respect to 32-bit addresses is very undefined. They act very
strangely and differently making it very difficult to safely figure
out if these cards are operating correctly or not.
No code changes for anything but the new A1200 version of the
library. (39.8)
- Bumped version to V40. (40.1)
- Two major bugs found in the A3000 memory test/CPU Card test.
Both were fixed. (40.1)
- CPU Card space is now able to be more than 128Meg. (We can grab
3 * 256Meg more since we don't start Zorro-III until $40000000
anyway...) (40.1)
- CPU Card space test now also does mirror testing. (40.1)
- Due to the fixes, some forms of the code have gotten a bit smaller,
specifically, the A3000, A4000, and A1200 versions. (40.1)
- Reworked the memory test to deal with extra-high capacitance
bus systems. (40.2)
Accidentally posted too early...
RAMSLOT seems to just be a chip select. I'm not sure why you wouldn't just decode it yourself, it seems of little help.