The following document was submitted by Dennis Armstrong.
Thanks to Frank Lockwood for putting me in touch with Dennis.

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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
       \----/
        U13
  

The 8 MB version of the board uses dynamic ram chips of a 1Mx4bit size.
Some compatible Part Numbers:

• MN414400-70
• TMS44400DM-10
• uPD424400AGS-80
• HM514410AT-8
• KM44C1000BV-8
• MB814400A-80
• TC514400AFT-80

[ Webmaster's note: it is possible to upgrade the 2 MB version to 8 MB, as explained here. ]

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

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