can someone explain system memory?

[teknicalissue]

i know a few things about building computer, but there is one thing that bugs me, how do i know which memory is great vs something horrible on the market. i heard about timings and CAS latency and voltage but inreality, i don't know a single thing about em, can someone please explain what i look for and why on system RAM?

 

[tastegw]

i know a few things about building computer, but there is one thing that bugs me, how do i know which memory is great vs something horrible on the market. i heard about timings and CAS latency and voltage but inreality, i don't know a single thing about em, can someone please explain what i look for and why on system RAM?

this may help you out

HowStuffWorks "How RAM Works"

 

[eyeCpc]

Sounds like you need a tutorial for a start. HowStuffWorks "How Computer Memory Works"

The first thing to know when going to buy memory is to know what the main system board will support as far as speeds and voltages as well as the type. The CAS Latency is part of the dram timings for memory.

The type of memory depends on the type of system like desktop or laptop seeing two different types between the two. Laptops/notebooks generally use 200pin sodimms while desktops use 184pin for DDR memory and 240pin for DDR2/DDR3 for more recent boards.

 

[teknicalissue]

i have that down, the types of ram compatible with the MotherBoards, compatibility has never been an issue, and TIMINGS thats the word i was looking for, i don't understand memory timings, ive built pretty good systems before so i know the basics for ram i just don't know anything with detail

 

[Fat.Clown]

lower timings = better (of the same speed)
lower voltage = better

how do i know which memory is great vs something horrible on the market

memory just works, it's just some overclock better than others
if you aren't overclocking, just pick up which ever is cheaper

timings basically it's how long the computer has to wait for the memory to refresh itself, and ready for next cycle
tighter timings you can get more cycles = faster

and then there is how fast(PC2-6400 vs PC2-1066) it process stuff, faster is better

so you want to find the perfect balance

here they go into more details
Memory Bandwidth vs. Latency Timings - PCSTATS.com

 

[teknicalissue]

cool =D thanks alot, just what i was looking for

 

[eyeCpc]

Once you buy a new set of dimms you may have to go into the bios to manually see the timings entered. For memory seeing timings of 5-5-5-15 this is how it would look wheh entering those in the dram timings section.

CAS# Latency(CL)=5
RAS# to CAS# Delay(tRCD)=5
RAS# Precharge(tRP)=5
Cycle Time (tRC)=15

The Command Rate is then set to 1T, 2T, or auto to avoid a need to clear the cmos information if set to the wrong one.

Some additional information on Ram TImings can be seen at Understanding RAM Timings | Hardware Secrets and at Memory Timings Explained