Dell OptiPlex 5270 All-in-One Service Manual page 9

Feature/Option
Multi-Purpose Register
DIMM Types
DIMM Pins
RAS
DDR4 Details
There are subtle differences between DDR3 and DDR4 memory modules, as listed below.
Key notch difference
The key notch on a DDR4 module is in a different location from the key notch on a DDR3 module. Both notches are on the insertion edge,
but the notch location on the DDR4 is slightly different, to prevent the module from being installed into an incompatible board or platform.
Figure 1. Notch difference
Increased thickness
DDR4 modules are slightly thicker than DDR3, to accommodate more signal layers.
Figure 2. Thickness difference
Curved edge
DDR4 modules feature a curved edge to help with insertion and alleviate stress on the PCB during memory installation.
Figure 3. Curved edge
DDR3
Four Registers – 1 Defined, 3
RFU
RDIMM, LRDIMM, UDIMM,
SODIMM
240 (R, LR, U); 204 (SODIMM)
ECC
DDR4
Four Registers – 3 Defined, 1
RFU
RDIMM, LRDIMM, UDIMM,
SODIMM
288 (R, LR, U); 260 (SODIMM)
CRC, Parity, Addressability,
GDM
DDR 4 Advantages
Provides Additional Specialty
Readout
More RAS features; improved
data integrity
Technology and components 9