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PCA-6185 User’s Manual 14
1.8 System Memory
The top-left edge of the PCA-6185 contains three sockets for 184-pin
dual inline memory modules (DIMMs). All these sockets accept only 2.5
V registered DDR SDRAM. Registered DIMMs are available in capaci-
ties of 128, 256, 512, 1024 or 2048 MB. The sockets can be filled in any
combination with DIMMs of any size, with the limitation of the total
memory capacity of 4 GB.
1.8.1 Sample calculation: DIMM memory capacity
Suppose you install a 128 MB DIMM into your PCA-6185's socket 1 and
a 256 MB DIMM into sockets 2 and 3. Your total system memory is 640
MB, calculated as follows:
Table 1.6: DIMM memory capacity sample calculation
Socket number 184-pin DIMM memory Total memory
1 128 MB x 1 128 MB
2 256 MB x 1 256 MB
3 256 MB x 1 256 MB
Total memory: 640 MB
1.8.2 Supplementary information about DIMMs
Your PCA-6185 can accept only registered DDR SDRAM memory mod-
ules. The register on the memory module secures reliable operation of
high memory capacity under high speed. Also note:
• Please use only DDR compliant registered DIMMS.
Most systems will not even boot if non-compliant modules are
used. This is due to strict timing issues involved at this speed.
• You can find two or three additional register ICs on a registered
SDRAM. These ICs are relatively smaller than the SDRAM ICs.
• Registered SDRAM are usually with ECC function. Modules with
9 or 18 SDRAM chips support ECC; modules with 8 or 16
SDRAM chips do not support ECC.
1.9 Memory Installation Procedures
To install DIMMs, first make sure the two handles of the DIMM socket
are in the "open" position. i.e. The handles lean outward. Slowly slide the
DIMM module along the plastic guides on both ends of the socket. Then
press the DIMM module right down into the socket, until you hear a
click. This is when the two handles have