memory - What are the quality metrics for RAM?

I have searched RAM and I found there are given some specification for the same capacity RAM, What are the difference and performance comparison between these?

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RAM1

General

Brand           Transcend
Memory Type     2 GB (8 x 128 MB) DDR2 DIMM
Memory Standard     DDR2-800/PC-6400
Compatible Device   PC
Pins            240-pin
Burst Length    4, 8
Buffered/Unbuffered Unbuffered

Memory

Memory Clock    400 MHz
Technology      DDR2 SDRAM Memory
CAS Latency     4, 5, 6

RAM 2

General

Brand              Transcend
Memory Type        2 GB (8 x 128 MB) DDR2 DIMM
Memory Standard    DDR2-667/PC2-5300
Compatible Device  PC
Pins               240-pin
Burst Length       4, 8
Buffered/Unbuffered    Unbuffered

Memory

Memory Clock    333 MHz
Technology      DDR2 SDRAM Memory
CAS Latency     3, 4, 5

RAM3

General

Brand           Kingston
Memory Type     2 GB (64 x 256 MB) 800 MHz DDR2 DIMM
Compatible Device   PC
Pins            240-pin
Error Check     Non-ECC
Buffered/Unbuffered  Unbuffered

Memory

Memory Clock    200 MHz
Technology      DDR2 SDRAM Memory
CAS Latency     6

What are the affect of the following

• Memory Type(given as 8 x 128 MB)


• Memory Clock (given in MHz)


• CAS Latency (given as 4,5,6)

my Requirement is 2 GB DDR2 Type Desktop/PC
Please suggest and help

Answer

CAS is the column access strobe and it is delay counter so less is faster. Mhz is the number of clock cycles per second and so more is faster, but the CPU and chipset control the maximum that is useful. Some CPU and chipset support 1066 and higher and others don't.

The clock speed will make more of a difference than CAS. The 66Mhz more in clock speed of RAM 1 won't generate that much more performance because it has CAS 4 and RAM 2 has CAS 3 as its lowest setting. How RAM 1 will probably be faster than RAM 2 but by a very tiny margin like 1%-5% percents. The CAS is 6 on RAM 3 so it is slower than RAM 1 given the total Mhz is 800mhz for both(RAM 1 and RAM 3.

The memory type is a simple internal layout of the memory and as far as I know has no effect on performance. However, if you were getting 8GB+ sticks of memory some motherboard don't support certain layouts.

Check your motherboard for maximum supported MHZ on the memory