Fast RAM for Amiga 3000
~~~~~~~~~~~~~~~~~~~~~~~
Via the U850D-U857D DIP package Bank 0 Sockets...
256Kbit x 4 20 pin DIP 80ns 8 1/1MByte
1Mbit x 4 20 pin DIP 80ns 8 1/4MBytes
Via the U850-U881 ZIP package Bank 0-3 Sockets...
256Kbit x 4 20 pin ZIP 80ns 8 4/4MBytes
1Mbit x 4 20 pin ZIP 80ns 8 4/16MBytes
These should all either be Static Column or Page Mode.
As noted above, some A3000's shipped with 1MByte of FAST memory in
DIP package, waiting to be transplanted into the sockets for CHIP RAM, once
more FAST RAM was installed. Those FAST memory sockets are the U850D-U857D
20 pin DIP places, Bank 0. This bank is electrically mapped to Bank 0
U850-U857, 20 pin ZIP sockets. As a result, one can make a three megabyte
A3000 configuration by putting 256Kbit x 4 chips into the FAST RAM DIP
sockets without buying ZIPs. Or a six meg setup, using 1MBit x 4 chips.
The DIP FAST sockets cannot be used with the ZIP sockets all together, as
the two Bank 0 areas are basically pinned to each other (as noted by the
same component numbers, one set with a D for DIP). One could have 4MBytes
of DIPs for FAST, then another 12MBytes of FAST in ZIPs placed into Banks
1-3, but not 4MBytes in the DIP area and 16MBytes in all four ZIP banks.
256Kbit and 1Mbit banks cannot be mixed. One cannot have 4MBytes of
1Mbit chips, and then 1MByte via another bank of 256Kbit chips. Of
course, one can't mix individual chips either! All four banks are either
low or high density banks.
