Last Updated: 2024-03-03

RAM = Random Access Memory.


DDR = Double data rate, transfering data on both the rising and falling edges of the clock signal.

Gen Capacity Clock Rate Voltage Release JEDEC standard OC modules
DDR6 2025? up to 12,800 MT/s up to 16,800 MT/s
DDR5 1.1 V 2020 up to 6,400 MT/s up to 8,4000 MT/s
DDR4 64 G 800-1600 MHz 1.2 V 2014 up to 3,200 MT/s up to 5,333 MT/s
DDR3 16 G 400-1066 MHz 1.5 V 2007 up to 2,133 MT/s up to 2,666 MT/s
DDR2 up to 1,066 MT/s up to 1,333 MT/s
DDR up to 400 MT/s up to 533 MT/s


  • 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


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 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



  • 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.