UPGRADING REPAIRING PCs

Table 2.17 Memory Bank Widths on Various Systems
Memory Types 45
30-Pin 72-Pin 168-Pin
Memory Memory SIMMs SIMMs SIMMs
Data Bank Size Bank Size per per per
Processor Bus (No Parity) (Parity) Bank Bank Bank
8088 8-bit 8 bits 9 bits 1 n/a n/a
8086 16-bit 16 bits 18 bits 2 n/a n/a
286 16-bit 16 bits 18 bits 2 n/a n/a
386SX,
SL, SLC
16-bit 16 bits 18 bits 2 n/a n/a
386DX 32-bit 32 bits 36 bits 4 1 n/a
486SLC,
SLC2
16-bit 16 bits 18 bits 2 n/a n/a
486SX,
DX, DX2,
DX4, 5x86
32-bit 32 bits 36 bits 4 1 n/a
Pentium, 64-bit 64 bits 72 bits 8 1
K5, K6
6x86,
6x86MX,
MII
2 1
Pentium 64-bit 64 bits 72 bits 8 1
Pro, PII,
PIII, Celeron,
Xeon, AMD
Athlon,
Duron, Intel
Itanium
2 1
1. Very few motherboards for these processors actually use this type of memory.
The number of bits for each bank can be made up of single chips, SIMMs, or DIMMs. Modern
systems don’t use individual chips; instead, they use only SIMMs or DIMMs. If the system has a
16-bit processor, such as a 386SX, it probably uses 30-pin SIMMs and has two SIMMs per bank.
All the SIMMs in a single bank must be the same size and type.
Memory Troubleshooting
Figure 2.12 provides basic steps that enable you to effectively test
and troubleshoot your system RAM. First, let’s cover the memory
testing and troubleshooting procedures.
After you’ve determined that the system’s memory is defective, you
need to determine which memory module is at fault. Follow the
procedure in Figure 2.13 to isolate the module for replacement.