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Without knowing the clock frequency it is impossible to state if one set of timings is "faster" than another. For example, DDR3-2000 memory has a 1000 MHz clock frequency, which yields a 1 ns clock cycle. With this 1 ns clock, a CAS latency of 7 gives an absolute CAS latency of 7 ns. Faster DDR3-2666 memory (with a 1333 MHz clock, or 0.75 ns ...
With data being transferred 64 bits at a time per memory module, DDR3 SDRAM gives a transfer rate of (memory clock rate) × 4 (for bus clock multiplier) × 2 (for data rate) × 64 (number of bits transferred) / 8 (number of bits in a byte). Thus with a memory clock frequency of 100 MHz, DDR3 SDRAM gives a maximum transfer rate of 6400 MB/s.
DDR SDRAM operating with a 100 MHz clock is called DDR-200 (after its 200 MT/s data transfer rate), and a 64-bit (8-byte) wide DIMM operated at that data rate is called PC-1600, after its 1600 MB/s peak (theoretical) bandwidth. Likewise, 12.8 GB/s transfer rate DDR3-1600 is called PC3-12800. Some examples of popular designations of DDR modules:
Because modern DRAM modules' CAS latencies are specified in clock ticks instead of time, ... DDR3-2000 2000 MT/s 0.500 ns 1000 MHz 1.000 ns 9 9.00 ns
DDR3 advances extended the ability to preserve internal clock rates while providing higher effective transfer rates by again doubling the prefetch depth. The DDR4 SDRAM is a high-speed dynamic random-access memory internally configured as 16 banks, 4 bank groups with 4 banks for each bank group for ×4/×8 and 8 banks, 2 bank groups with 4 ...
2000 Mbit/s: 250 MB/s: 2019 GPON ... only one module at a time can transfer information to the CPU. In multi-channel configurations, multiple modules can transfer ...
At higher clock rates, the useful CAS latency in clock cycles naturally increases. 10–15 ns is 2–3 cycles (CL2–3) of the 200 MHz clock of DDR-400 SDRAM, CL4-6 for DDR2-800, and CL8-12 for DDR3-1600. Slower clock cycles will naturally allow lower numbers of CAS latency cycles.
Then, the base memory clock will operate at (Memory Divider) × (FSB) = 1 × 200 = 200 MHz and the effective memory clock would be 400 MHz since it is a DDR system ("DDR" stands for Double Data Rate; the effective memory clock speed is double the actual clock speed). The CPU will operate at 10 × 200 MHz = 2.0 GHz.