Why are RAM latencies going upwards?

reflekshun · Dec 11, 2012, 07:42 PM

I am wondering what the reason is that RAM latencies are generally getting higher as the years go on, is it related to RAM size?

Will there be much benefit to my memory intensive audio workstation if I get lower latency ram or is there a trade off (higher CPU usage etc.) if i get lower latency RAM?

I'm considering buying 32GB of CS 10 ram instead of CS 11 RAM for the new 27" imac.

Many thanks for any ideas / info!

Puevlo · Dec 11, 2012, 09:30 PM

They're not going upwards. RAM latency is decreasing as clock speeds are increasing.

drambuie · Dec 11, 2012, 10:16 PM

The latencies are the delays in clock cycles caused by the time it takes for the RAM chips to perform specific functions. Although clock speeds are increasing, the RAM silicon speed isn't increasing much. Therefore it takes more clock cycles to perform the same tasks. A clock frequency of 1333MHz with a latency of 9 equates to a memory response time of 6.75ns. A speed of 1600MHz at a CL of 11 equates to a 6.78ns response. Compared to desktop DIMMS with their overclocking abilities, SODIMMS presently have limited speed/latency options. You can get high speed, low latency desktop DIMMS if you're willing to pay the extra price.

reflekshun · Dec 12, 2012, 04:03 AM

Thanks drambuie a great detailed answer, exactly what I was looking for.

Now it's down to the question of whether I trust any other brands more than OWC for RAM, as OWC is only selling CL 11 RAM for the new imac!

Thanks again

Dec 11, 2012, 07:42 PM	#1
reflekshun macrumors member Join Date: Sep 2010	Why are RAM latencies going upwards? I am wondering what the reason is that RAM latencies are generally getting higher as the years go on, is it related to RAM size? Will there be much benefit to my memory intensive audio workstation if I get lower latency ram or is there a trade off (higher CPU usage etc.) if i get lower latency RAM? I'm considering buying 32GB of CS 10 ram instead of CS 11 RAM for the new 27" imac. Many thanks for any ideas / info!
	1

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Dec 11, 2012, 09:30 PM	#2
Puevlo macrumors 6502a Join Date: Oct 2011	They're not going upwards. RAM latency is decreasing as clock speeds are increasing.
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Dec 11, 2012, 10:16 PM	#3
drambuie macrumors 6502a Join Date: Feb 2010	The latencies are the delays in clock cycles caused by the time it takes for the RAM chips to perform specific functions. Although clock speeds are increasing, the RAM silicon speed isn't increasing much. Therefore it takes more clock cycles to perform the same tasks. A clock frequency of 1333MHz with a latency of 9 equates to a memory response time of 6.75ns. A speed of 1600MHz at a CL of 11 equates to a 6.78ns response. Compared to desktop DIMMS with their overclocking abilities, SODIMMS presently have limited speed/latency options. You can get high speed, low latency desktop DIMMS if you're willing to pay the extra price.
	4

Dec 12, 2012, 04:03 AM	#4
reflekshun Thread Starter macrumors member Join Date: Sep 2010	Thanks drambuie a great detailed answer, exactly what I was looking for. Now it's down to the question of whether I trust any other brands more than OWC for RAM, as OWC is only selling CL 11 RAM for the new imac! Thanks again
	0