The following document was submitted by Dennis Armstrong.
Thanks to Frank Lockwood for putting me in touch with Dennis.
The ST RAM
For its ST-compatible memory, the TT motherboard uses dynamic ram chips of a 256Kx4bit size.
Some compatible Part Numbers:
- TMS44C256-10N
- uPD424256C-80
- M5M44256BP-70
[ Webmaster's note: Jim DeClercq sent me something about upgrading the motherboard to 8 MB ]
ST RAM Daughterboards (2 MB and 8 MB)
ATARI offered two daughterboards to raise the ST memory configuration to 4 MB or 10 MB.
2 MB Board (CA400313-xxx)
Uses the same memory chips as on the motherboard; no configuration headers are required.
2/8 MB Board (CA401059-xxx)
The board contains the following jumpers to select the 2MB or 8MB memory configuration:
jumper 2 MB 8 MB W1 1-2 2-3 W2 open 2-3 Location:
| | | | W1 W2 | | 3 3 | | 2 2 | | 1 1 \----/ U13The 8 MB version of the board uses dynamic ram chips of a 1Mx4bit size.
Some compatible Part Numbers:[ Webmaster's note: it is possible to upgrade the 2 MB version to 8 MB, as explained here. ]
- MN414400-70
- TMS44400DM-10
- uPD424400AGS-80
- HM514410AT-8
- KM44C1000BV-8
- MB814400A-80
- TC514400AFT-80
ST RAM Addresses
Address Function Base system 000008 - 000800 System Memory 000800 - 1FFFFF Motherboard (2 MB)
Address Function 4 MB system 1FFFFF - 3FFFFF 2 MB Expansion 800000 - 9FFFFF Motherboard
Address Function 10 MB system 000000 - 7FFFFF 8 MB Expansion 800000 - 9FFFFF Motherboard