HP Compaq d538 MT Hardware Reference Manual page 27

Hardware Reference Guide
There are four DIMM sockets on the system board, with two sockets
per channel. The sockets are labeled XMM1, XMM2, XMM3, and
XMM4. Sockets XMM1 and XMM2 operate in memory channel A.
Sockets XMM3 and XMM4 operate in memory channel B.
DIMM Socket Locations
Item Description
DIMM socket XMM1, Channel A
1
DIMM socket XMM2, Channel A
2
DIMM socket XMM3, Channel B
3
DIMM socket XMM4, Channel B
4
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Hardware Upgrades
Socket Color
Black
Blue
Black
Blue
2–9