Question about RAMFollow

RAM speed is measured in nano seconds (ns). The fewer, the better, the faster.

Here are two of the most common RAM speeds:.

200Mhz = 5ns
250Mhz = 4ns.

Two common Latencies for these speeds:.

200MHz = 2-2-2-5
250MHz = 2.5-3-3-7.

Primary Latencies:
tCAS - the number of clock cycles needed to access a certain column of Data in RAM. CAS Latency, or simply CAS, is known as Column Address Strobe Latency, sometimes refered to as tCL. In 2.5-3-3-7, this is the 2.5.
tRCD - the number of Clock cycles needed between RAS and CAS. It is the time required between the computer defining the row and column of the given memory block and the actual read or write to that location. Stands for Row address to Column address Delay. In 2.5-3-3-7, this is the first 3.
tRP - the number of clock cycles needed to terminate access an open row of memory, and open access to the next row. Stands for Row precharge time. In 2.5-3-3-7, this is the second 3.
tRAS - the miniumum number of clock cycles needed to access certain row of data in RAM between the data request and the precharge command. Known as Active to Precharge Delay In 2.5-3-3-7, this is the 7.
.
So therefore:.
2 cycles @ 200Mhz = 10ns
2 cycles @ 200Mhz = 10ns
2 cycles @ 200Mhz = 10ns
5 cycles @ 200Mhz = 25ns.

2.5 cycles @ 250Mhz = 10ns
3 cycles @ 250Mhz = 12ns
3 cycles @ 250Mhz = 12ns
7 cycles @ 250Mhz = 28ns.

So in terms of only the memory/ data access / latencies have gone up a bit. This is slightly slower..
Proportionally 2-2-2-5 @ 200Mhz translates to 2.5 - 2.5 - 2.5 - 6.25 @ 250Mhz. This would be the same..

2.5 cycles @ 250Mhz = 10ns
2.5 cycles @ 250Mhz = 10ns
2.5 cycles @ 250Mhz = 10ns
6.25 cycles @ 250Mhz = 25ns