More Speed = Greater Timings?

[e56imfg]

How come all the extremely high speed RAM modules have more timings than a lower speed RAM module? Isn't lower timings better? What are timings used for? What's the difference between the speed and the timings?

 

[blazorthon]

What you're referring to as speed is actually the frequency/data rate, aka how many clock cycles are done each second. Data is transferred twice every clock cycle in all DDR, DDR2, and DDR3 modules. Timings are latency, measured in clock cycles.

Take PC3-12800, aka 1600MHz DDR3 memory for example. It is actually running at 800MHz but since it has two data transfers per clock cycle instead of one we just call it 1600MHz for simplicity. DDR means double data rate. SDRAM (the memory tech before DDR memory) was SDR aka single data rate. It ran up to 133MHz. DDR maxes out at 200MHz actual frequency but since it's DDR it is called 400MHz. Memory manufacturers and other companies did this when DDR came out so people would know that SDRAM and DDR RAM at the same frequency was not the same speed.

Latencies the amounts of clock cycles that certain functions in the RAM take up to execute. Higher timings means it takes longer to do each function. Higher frequency with the same timings takes less time because even though it takes say 9 clock cycles to address a new column (CAS latency), each clock cycle goes faster on the higher frequency memory.

That is why very high frequency RAM often has high timings, it huge frequency counteracts the high timings. This is the simplified, short explanation. If you want a longer one just ask and I'll get on it.

 

[e56imfg]

Best answer selected by e56imfg.

 

[e56imfg]

Wow, thanks for the awesome reply. I think I got it now

 

[blazorthon]

Your welcome.

 

[nikorr]

This topic has been closed by Nikorr.