Hardware Reference
In-Depth Information
chips on the module (usually from one to three, depending on the module design). In this
example, the part number turns out to be a Micron memory chip that decodes like this:
MT = Micron Technologies (the memory chip maker)
46 = DDR SDRAM
V = 2.5V DC
64M8 = 8 million rows × 8 (equals 64) × 8 banks (often written as 64 Meg × 8)
TG = 66-pin TSOP chip package
-75 = 7.5ns @ CL2 latency (DDR 266)
The full datasheet for this example is located at
http://download.micron.com/pdf/data-
From this information, you can determine that the module has the following characterist-
ics:
• The module runs at DDR266 speeds using standard 2.5V DC voltage.
• The module has a latency of CL2, so you can use it on any system that requires CL2
or slower latency (such as CL2.5 or CL3).
• Each chip has a capacity of 512Mb (64 × 8 = 512).
• Each chip contains 8 bits. Because it takes 8 bits to make 1 byte, you can calculate the
capacity of the module by grouping the memory chips on the module into groups of
eight. If each chip contains 512Mb, a group of eight means that the module has a size
of 512MB (512Mb × 8 = 512MB). A dual-bank module has two groups of eight chips
for a capacity of 1GB (512Mb × 8 = 1024MB, or 1GB).
If the module has nine instead of eight memory chips (or 18 instead of 16), the additional
chips are used for parity checking and support ECC error correction on servers with this
feature.
To determine the size of the module in megabytes or gigabytes and to determine whether
the module supports ECC, count the memory chips on the module and compare them to
Table 6.12
.
Note that the size of each memory chip in megabits is the same as the size in
megabytes if the memory chips use an 8-bit design.
Table 6.12 Module Capacity Using 512Mb (64Mbit × 8) Chips
