486SLC CPU Upgrade

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PS/2 8555 486SLC Upgrade Performance Failure H127022

IBM PS/2 8555SX systems may fail to function at an increased processor speed after installing 486SLC processor upgrade.

Problem Isolation Aids

A limited number of PS/2 8555SX system boards contain a module located to the left of the memory SIMM sockets labeled "Pinto 3A #64F3646." This chip may conflict with the bus timings of the 486SLC Processor upgrade which results in a reduction in processor performance. The "Pinto 3A" chip only affects IBM option P/N 13H6694, FRU P/N 13H6697, card assembly P/N 78G2521.

       _________________________________________
      |                                        _|_______System Board
      |       ___________                       |
      |      (___________)Fuse                  |
      |                          Memory Sockets |
      |     ______________       __  |   __     |
      |    |              |     |  |    |  |    |
      |    |              |     |  |    |  |    |
      |    |   PINTO 3A   |     |  |    |  |    |
      |    |   64F3646    |     |  |    |  |    |
      |    |              |     |  |    |  |    |
      |    |              |     |  |    |  |    |
      |    |______________|     |  |    |  |    |
      |                         |  |    |  |    |
      |                         |  |    |  |    |
      |                         |__|    |__|    |
      |_________________________________________|

The record says the affected planars were removed from stock. There are two main variants of the 8555 SX, the Early (ZM16) and Late (ZM22) planars. Both of my sample boards do not have 64F3646.

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Last update: 26 Oct 2021 - Changes & Credits | Legal Info & Contact