RAM Generations
All computer devices use random-access memory (RAM) to store the short-term data. As computer process evolve, RAM improves too. Each generation of RAM increases speed and frequency while decreasing power consumption.
This page summarize the differences between the generations of RAM[1].
| Generation | History | Prefetch | Data Rate(MT/s) | Transfer Rate (GB/s) | Voltage (V) |
|---|---|---|---|---|---|
| SDRAM
(Synchronous Dynamic Random Access Memory) |
1988 | 1 - Bit | 100 - 166 | 0.8 - 1.3 | 3.3 |
| DDR
(Double Data Rate) |
2000 | 2 - Bit | 266 - 400 | 2.1 - 3.2 | 2.5 - 2.6 |
| DDR2 | 2003 | 4 - Bit | 533 - 800 | 4.2 - 6.4 | 1.8 |
| DDR3 | 2007 | 8 - Bit | 1066 - 1600 | 8.5 - 14.9 | 1.35 - 1.5 |
| DDR4 | 2014 | Bit per Bank | 2133 - 5100 | 17 - 25.6 | 1.2 |
| DDR5 | 2021 | 16 - Bit | 3200 - 6400 | 38.4 - 51.2 | 1.1 |
CAS (Column Address Signal) Latency
DDR4’s major advantage over DDR5 is its lower latency. The lower the latency, the faster the CPU can access the instructions it temporarily stored in the RAM to perform the tasks. Total latency is determined by both a DIMM module’s speed and its CAS (Column Address Signal) latency. For CAS latency ratings, lower numbers are better.
A DDR4-3200 CL20 module, for instance, has a CAS latency rating of 20. Most DDR5 modules have CL40 CAS latency. So, that DDR4-3200 CL20 RAM will have snappier performance than a DDR5-4800 CL40 module.
Capacity vs Latency
Although DDR4 tops out at 64GB per module (RAM stick), DDR5 can top out at a whopping 512GB per module. Better specs are great, but they won’t matter if they don’t translate into better performance. Because of DDR5’s high latencies, its performance is not notably better than DDR4 modules.
A report said their Nvidia-based graphics benchmarks systems actually performed worse on DDR5 setup than DDR4.