General Definition inside RAM

after a day problem with the blogger, now Inside the Computers will continue, and now we will go to the General Definition inside RAM, including Speed, PC Rating and CAS Latency.

General Definitions on RAM
So many name and specific definition that we know on RAM, sometimes that make us confuse.   But no need to worry, I will explain the General Definitions here; at least after we read this articles, we can read the specification and the ability of the product of RAM.

Speed
Speed is become one of the important thing if we select a memory module. Faster the CPU, plus with the developed that use on dual core, makes RAM has to have ability faster to serving the CPU. There are a few important parameters who will affect the speed of a memory.
Megahertz (MHz)

This term use start with the SDRAM, the speed of memory (SDRAM) still on Megahertz (MHz), and still use even with the DDR2 period. The calculate base on time period which needed between clock cycle. Usually use time period nanosecond. For example, on the memory with actual clock speed 133 MHz will use 8 nanosecond (ns) for 1 clock cycle.

 Later the SDRAM present will replace with DDR (Double Data Rate). With the main development on the ability to send the data more in other word, double. DDR send the data twice in one clock cycle. The DDR2 also use the same method, which is the result of develops from DDR. With the main advantage is low temperature when they work. Also with the capacity of chi memory on DDR2 which increase drastically, it’s possibly that a one DDR2 has capacity until 2 Gb, even more, and DDR2 also have a progress on the speed compare with the previous DDR.

PC RATING
On the DDR module, is often that we seen on the memory written PC3200. For DDR2 module, PC2-3200, so where the number is comes? Use to know as PC RATING for DDR and DDR2 module. For the example, now a DDR module with clock speed 200 MHz, or for DDR Rating called DDR400, with bus width is 64-bit, so the ability of data transfer is 25,600 megabit per second (=400 MHz x 64-bit). With 1 byte = 8-bit, same with 3,200MBps (Megabyte per second). This throughput number is value of PC Rating. The placement of number 2 on DDR2 is just to make the different between DDR and DDR2.

CAS LATENCY
CAS = column address strobe or column address select. The meaning of that acronym is the same, which is the specific location from array data on DRAM module. CAS Latency or we use to know with CL, is amount of time which needed (clock cycle) during the delay between data request when send to memory controller for read process until the memory module is succeed produce the data output. If the CL specification on the RAM module is lower and with the same speed, that will be resulted faster memory.