With DDR3 reaching its limits in a world that demands higher performance and increased bandwidth, a new generation of DDR SDRAM has arrived. DDR4 delivers higher performance, higher DIMM capacities, improved data integrity and lower power consumption.
In addition to optimized performance and greener, low-cost computing, DDR4 also provides cyclic redundancy checks (CRC) for improved data reliability, on-chip parity detection for integrity verification of ‘command and address’ transfers over a link, enhanced signal integrity and other robust RAS features.
Please note that there are subtle differences between DDR3 and DDR4 modules.
|Chip Densities||512Mb-8Gb||4Gb-16Gb||Larger DIMM Capacities|
|Data Rates||800Mb/s – 2133Mb/s||1600Mb/s – 3200Mb/s||Migration to Higher-Speed I/O|
|Voltage||1,5V||1,2V||Reduced Memory Power Demand|
|Low Voltage Standard||Yes (DDR3L at 1.35V)||Anticipated at 1.05V||Memory Power Reductions|
|Internal Banks||8||16||More Banks|
|Bank Groups (BG)||0||4||Faster Burst Accesses|
|VREF inputs||2 – DQs and CMD/ADDR||1 – CMD/ADDR||VREFDQ Now Internal|
|tCK – DLL Enabled||300MHz – 800MHz||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 Ω||48 Ω||Optimal for PtP Applications|
|DQ Bus||SSTL15||POD12||Less I/O Noise and Power|
|RTT Values (in Ω)||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|