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Memory

Updated: 2022-07-30

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