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PB 386 25/33 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. SHADOW BIOS Enabled DOES NOT affect Extended Memory.
 
2. No jumper setting required.
 
3. Recommended SIMM speed is 80ns.
 
4. The Users Manual Shows a configuration with the 256K SIMMs in bank 0 and the 1MB SIMMs in bank 1. This configuration will work but may cause intermittent memory situations.
 

Upgrade Table

TOTAL

SIMMs

EXTENDED

MEMORY

BANK 0

BANK 1

MEMORY
1MB (4)256K X 9 0 KB
2MB (4)256K X 9 (4)256K X 9 1024
4MB (4) 1MB X 9 3072
5MB (4) 1MB X 9 (4)256K X 9 4096
8MB (4) 1MB X 9 (4) 1MB X 9 7168
16MB (4) 4MB X 9 15360
20MB (4) 1MB X 9 (4) 4MB X 9 19456
32MB (4) 4MB X 9 (4) 4MB X 9 31744
 
 
Two different configurations of SIMM sockets are being used on PB33 motherboards.
One configuration of SIMM socket accepts only a specific type of SIMM.
If the system memory is upgraded using the incorrect type of SIMM the additional memory may not be recognized.
If the memory is not recognized by the system or if memory errors occur and the SIMMs are not one of the recommended types listed below, the SIMM socket may be the cause of the errors.
Please refer to the following list of SIMMs when recommending memory upgrades for this system.
The SIMMs listed below will work with either type of socket configuration.  
 

256K SIMM
Manufacturer Part Number
Hitachi HB56D25609B-85A
NMBS MM256K0J9S-08H

1MB SIMM
Manufacturer Part Number
Intel ISM001DR09PHH70
Mitsubishi MH1M09A0J-80
Motorola MCM91000S
NMBS MM1M200J9S-08H
Panasonic MN4A091M0S80
Siemens HYM91000S-70
Toshiba THM91000S-80