Table 4. DDR3 vs DDR4 (continued)
Feature/Option
DDR3
DDR4
DDR 4 Advantages
DQ Bus
SSTL15
POD12
Less I/O Noise and Power
RTT Values (in &Omega)
120,60,40,30,20
240,120,80,60,48,40,34
Support for higher data rates
RTT not allowed
READ Bursts
Disables during READ Bursts
Ease of use
ODT Modes
Nominal, Dynamic
Nominal, Dynamic,Park
Add’l Control Mode; OTF
Value Change
ODT Control
ODT Signaling Required
ODT Signaling Not Required
Ease of ODT Control; Allows
Non-ODT Routing, PtP Apps
Multi-Purpose Register
Four Registers – 1 Defined, 3
RFU
Four Registers – 3 Defined, 1
RFU
Provides Additional Specialty
Readout
DIMM Types
RDIMM, LRDIMM, UDIMM,
SODIMM
RDIMM, LRDIMM, UDIMM,
SODIMM
DIMM Pins
240 (R, LR, U); 204
(SODIMM)
288 (R, LR, U); 260
(SODIMM)
RAS
ECC
CRC, Parity, Addressability,
GDM
More RAS features; improved
data integrity
DDR4 Details
There are subtle differences between DDR3 and DDR4 memory modules, as listed below.
Key notch differenc
e
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.
Technology and components
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