Memory
Last Updated: 2023-02-20
RAM = Random Access Memory.
DDR
DDR = Double data rate, transfering data on both the rising and falling edges of the clock signal.
| Generation | Max Capacity | Clock Rate | Voltage | Release Time |
|---|---|---|---|---|
| DDR5 | 1.1 V | 2020 | ||
| DDR4 | 64 G | 800-1600 MHz | 1.2 V | 2014 |
| DDR3 | 16 G | 400-1066 MHz | 1.5 V | 2007 |
DDR vs GDDR
- G is for graphics and GDDR is for GPU; DDR is on the motherboard and is for CPU.
- GDDR is designed for use by RISC (Reduced Instruction Set Computers) machines and DDR by CISC (Complex Instruction Set Computers). RISC machines perform one operation per tick, CISC machines perform multiple operations per tick. GDDR is very fast at dealing with the “one tick, one operation” workloads. DDR is very fast at dealing with “one tick, multiple operation” workloads
- GDDR is built for much higher bandwidth, with a wider memory bus.
- GDDR has lower power and heat dispersal requirements compared to DDR, allowing for higher performance modules, with simpler cooling systems.
- GDDR can request and receive data on the same clock cycle, where DDR cannot.
- GDDR being optimized for bandwidth while DDR is optimized for latency
DDR vs LPDDR
LP = Low-Power.
- LPDDR consumes less power and is targeted for mobile devices like smartphones, tablets
- DDR has a 64-bit wide memory bus, LPDDR also permits 16- or 32-bit wide channels
Optane
Optane memory could replace DDR DRAM, retains data even if a computer is shut off
Memory Bandwidth
| RAM | Bandwidth |
|---|---|
| M1 Max | 400 GB /s |
| M1 Pro | 200 GB /s |
| DDR5-6400 | 51.2 GB/s |
| DDR5-5200 | 41.6 GB/s |
| DDR4-3200 | 25.6 GB/s |
| DDR4-2666 | 21.3 GB/s |
| DDR4-2400 | 19.2 GB/s |
| DDR4-2133 | 17 GB/s |
| DDR3-1866 | 14.9 GB/s |
| DDR3-1600 | 12.8 GB/s |
| DDR3-1333 | 10.6 GB/s |
| DDR3-1066 | 8.5 GB/s |
| DDR2-800 | 6.4 GB/s |
| DDR2-667 | 5.33 GB/s |
| DDR2-533 | 4.27 GB/s |
| DDR-400 | 3.2 GB/s |
| DDR-333 | 2.7GB/s |
| DDR-266 | 2.1 GB/s |
Calculation:
e.g.
- DDR4-3200:
3200 * 64 bit / (8 bits / byte) = 25.6 GB/s - DDR3-1333:
1333 * 64 bit / (8 bits / byte) = 10.6 GB/s
Other Specs
CL: the RAM kit’s CAS (Column Address Strobe or Signal) latency, i.e. how many clock cycles in it takes for the RAM module to access a specific set of data in one of its columns. The lower the better.