WARNING: This information is provided "as is" with no warranty. Use at your own risk!
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PB55 Upgrade Information

Battery

BIOS
Cache

CPU

RAM
Video

PB55 RAM Memory Upgrade

Warning Only authorized service personnel should upgrade the system. Anyone who wants to upgrade the system herself/himself should know about the dangers of ESD (Electro-Static Discharge) and the necessary precautions. Unknowingly zapping the components of the computer will void the warranty.

Specifications

  1. BASE MEMORY=640 (always)
   2. SHADOW BIOS Enabled takes 128Kb off of Extended Memory.
   3. No jumper setting required.
  4. Recommended SIMM speed is 80ns.

Upgrade Table

TOTAL SIMMS EXTENDED
MEMORY BANK 0 BANK 1 MEMORY
1MB (2)256K X 9 (2)256K X 9 384
2MB (2) 1MB X 9 1408
2.5MB (2) 1MB X 9 (2)256K X 9 1920
4MB (2) 1MB X 9 (2) 1MB X 9 3456
8MB (2) 4MB X 9 7552
8.5MB (2) 4MB X 9 (2)256K X 9 8064
10MB (2) 4MB X 9 (2) 1MB X 9 9600
16MB (2) 4MB X 9 (2) 4MB X 9 15744

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PB55 CPU Upgrade

Warning Only authorized service personnel should upgrade the system. Anyone who wants to upgrade the system herself/himself should know about the dangers of ESD (Electro-Static Discharge) and the necessary precautions. Unknowingly zapping the components of the computer will void the warranty.

NOTE

This system supports the 80387SX-20 math co-processor. It is installed at location U42. No jumper settings are required.
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PB55 Battery Upgrade

Warning Only authorized service personnel should upgrade the system. Anyone who wants to upgrade the system herself/himself should know about the dangers of ESD (Electro-Static Discharge) and the necessary precautions. Unknowingly zapping the components of the computer will void the warranty.
Tadiran 3.6V Lithium connected at location J16.
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PB55 Cache Memory Upgrade

Warning Only authorized service personnel should upgrade the system. Anyone who wants to upgrade the system herself/himself should know about the dangers of ESD (Electro-Static Discharge) and the necessary precautions. Unknowingly zapping the components of the computer will void the warranty.

Specifications

There are two 28-pin SRAM sockets, which upgrades the 16K cache to 32K, located at U48 and U53 on the motherboard of the PB55.
The table below shows some of the chip manufacturers and the chip numbers. If our end-users are having difficulty finding any of these chips from local dealers, please refer them to:
AMT International Chip Manufacturer
Chip Number Cypress CY7C185-25PC
Micron MT5C6408-25
ISSI IS61C64-20N
IDT IDT7164S25TP
Mitsubishi M5M5178P-20

NOTE

The speed of the SRAM chips must be 25ns or faster.

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