2500 SX/25 (250-1610)           Memory                 Faxback Doc. # 1124

Memory Chip Kits - 

256K SIMMS
     **25-5135 consists of two 256K X 9 SIMM chips at 80 nanoseconds. 
     RSU # 11388519 (one SIMM)

1MB SIMMS 
     25-5137 consists of two 1 MB x 9 SIMM chips at 60 nanoseconds.
     RSU # 10542355

4MB SIMMS
     **25-5136 consists of two 4 MB x 9 SIMM chips at 60 nanoseconds.  This
         product can be obtained from Tandy National Parts.
     RSU # 10542348

** = Discontinued Radio Shack product

 +-----------------------------------+
 | Tandy 2500SX/25 - Expand from 2MB:|
 |-----------------------------------|
 |          Add to         Add to    |
 |         Bank 1(A)      Bank 2(B)  |
 |-----------------------------------|
 | 4MB   | 25-5137           N/A     |
 |-------+---------------------------|
 | 4.5MB | 25-5137        25-5135    |
 |-------+---------------------------|
 | 6MB   | 25-5137        25-5137    |
 |-------+---------------------------|
 |10MB   | 25-5136           N/A     |
 |-------+---------------------------|
 |12MB   | 25-5137        25-5136    |
 |-------+---------------------------|
 |16MB*  | 25-5136        25-5136    |
 +-----------------------------------+

Note: Although the logical amount should be 18 MB, (16 MB + 2 MB on board)
      the 2500 SX/25 will only access 16 MB of memory. This is because the
      2500 SX/25 uses an 80386 SX style processor. The SX processor has
      only 24 address lines available, this limits memory access to 16 MB.

You cannot upgrade memory using 256KB SIMMs in Bank A. Do not mix 256KB,
1MB, and 4MB SIMMs in the same bank on the main logic board.  Run the
setup utility after installing memory.

The main logic board has 2MB of permanently installed memory in Bank 0.
Four empty SIMM sockets (Banks 1 and 2) are available for installing
256KB, 1MB, or 4MB, 70ns SIMMs.

Banks 1 and 2 are labeled A and B on the main logic board.

The following table lists the SIMMs required for each memory configuration:

 +------------------------------------------------+
 | TOTAL |             |           |TOTAL NUMBER  |
 | MEMORY|  BANK 1 (A) | BANK 2 (B)|  OF SIMMs    |
 |-------+-------------+-----------+--------------|
 | 4MB   |  Two 1MB    |  Empty    |       2      |
 |-------+-------------+-----------+--------------|
 | 4.5 MB|  Two 1MB    |  Two 256KB|       4      |
 |-------+-------------+-----------+--------------|
 | 6MB   |  Two 1MB    |  Two 1MB  |       4      |
 |-------+-------------+-----------+--------------|
 | 10MB  |  Two 4MB    |  Empty    |       2      |
 |-------+-------------+-----------+--------------|
 | 12MB  |  Two 1MB    |  Two 4MB  |       4      |
 |-------+-------------+-----------+--------------|
 | 16MB  |  Two 4MB    |  Two 4MB  |       4      |
 +------------------------------------------------+

Install the SIMMs as described in your SIMM kit installation guide. 

After installing the SIMMs, run the SetupSX program on MS-DOS Disk 1.
SetupSX completes the installation by ensuring that the new memory is
recognized in the system. Refer to "SetupSX" in the "Utilities" section.

(RJS/tmc-02/16/95)

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