I've been searching for the last few days and haven't found a definitive answer. The question is all about RAM timings and basically is the more aggressive timings worth the price difference and will I (or the average user) see a difference in real world gaming & app / program usage?
The computer in question is a Toshiba L855D-S5114 Laptop
AMD A8-4500M @ 1.9ghz (2.8ghz Boost)
AMD 7640G APU 4gb 1600 Single Channel
640gb 5400rpm SATA HDD
The rest I know is insignificant
I purchased the laptop for $379.99 from Best Buy which I think is a great deal for an A8. The problem is the RAM. I've done a lot of research that says that APU's more than anything benefit from faster RAM speeds and Dual Channel. I gathered a couple Dual Channel kits but again, the question arose in my mind, does the RAM Timing increase performance as much as the RAM Speed?
(All listings are 2x4gb Dual Channel Kits @ 1600mhz)
speed and low CL are what you are looking for. the lower the timings (CL) the faster they are. IE DDR3 1066 has a data transfer rate of 1066 MT. 1333 is just that 1333 MT and so on. then you have CL (CAS Latency) which is the number in ns or nanoseconds. While the typical latencies for a JEDEC DDR2 device were 5-5-5-15, some standard latencies for JEDEC DDR3 devices include 7-7-7-20 for DDR3-1066 and 8-8-8-24 for DDR3-1333.
DDR3 latencies are numerically higher because the I/O bus clock cycles by which they are measured are shorter; the actual time interval is similar to DDR2 latencies (around 10 ns). There is some improvement because DDR3 generally uses more recent manufacturing processes, but this is not directly caused by the change to DDR3.
As with earlier memory generations, faster DDR3 memory became available after the release of the initial versions. DDR3-2000 memory with 9-9-9-28 latency (9 ns) was available in time to coincide with the Intel Core i7 release. CAS latency of 9 at 1000 MHz (DDR3-2000) is 9 ns, while CAS latency of 7 at 667 MHz (DDR3-1333) is 10.5 ns.
(CAS / Frequency (MHz)) × 1000 = X ns
(7 / 667) × 1000 = 10.4948 ns
so you need speed plus the lowest cl for the best performance.
From my experiece, RAM timings difference is in nano seconds, you should look for higher max size and max speed MHz supported by the mobo. Timing really does not matter for apps and program use, but for high end games there will be difference in the frame rates a bit.
I went ahead and pulled the trigger on the Corsair 9-9-9-24. I found it on eBay (new from a high rated seller) for $49.99 with no tax and free shipping. I plan on running a few benchmarks before and after the upgrade to see what kind of impact it made on the CPU & APU.