DDR4 (double data rate fourth generation) memory is a higher-speed
successor to the DDR2 and DDR3 technologies and allows up to 512 GB
in capacity, compared to the DDR3's maximum capacity of 128 GB per DIMM. DDR4
synchronous dynamic random-access memory is keyed differently from
both SDRAM and DDR to prevent the user from installing the wrong type
of memory into the system.
DDR4 needs 20 percent
less or just 1.2 volts, compared to DDR3 which requires 1.5 volts
of electrical power to operate. DDR4 also supports a new, deep power-down
mode that allows the host device to go into standby without needing
to refresh its memory. Deep power-down mode is expected to reduce
standby power consumption by 40 to 50 percent.
Key Specifications
The following table lists the specifications' comparison
between DDR3 and DDR4:
Table 1. DDR3 vs DDR4This table describes you comparison between DDR3 vs DDR4
Feature/Option
DDR3
DDR4
DDR 4 Advantages
Chip Densities
512 Mb-8 Gb
4 Gb-16 Gb
Larger DIMM capacities
Data rates
800 Mb/s-2133 Mb/s
1600 Mb/s-3200 Mb/s
Migration to higher speed I/O
Voltage
1.5 V
1.2 V
Reduced memory power demand
Low voltage standard
Yes (DDR3L at 1.35V)
Anticipated at 1.05V
Memory Power Reductions
Internal banks
8
16
Higher data rates
Bank groups (BG)
0
4
Faster burst accesses
VREF inputs
2 —DQs and CMD/ADDR
1 — CMD/ADDR
VREFDQ Now Internal
tCK — DLL Enabled
300 Mhz-800 Mhz
667Mhz-1.6Ghz
Higher data rates
tCK — DLL Disabled
10MHz – 125MHz (optional)
Undefined to 125MHz
DLL-off now fully supported
Read Latency
AL+CL
AL+CL
Expanded values
Write Latency
AL+CWL
AL+CWL
Expanded values
DQ Driver (ALT)
40&Omega
48&Omega
Optimal for PtP Applications
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 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
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