PC-8500 vs PC-12800 RAM on an older Macbook Pro

Thanks.

A more general question would be, how much does the CAS latency affect the memory speed of any machine, not only MacBook, and not only Apple.

I.e. if the motherboard only supports up to PC3-8500 which is 1067 Mhz, will a memory module with PC3-12800 (which of course will work only at 1067 Mhz, not 1600 Mhz) perform slower than a PC3-8500 module due to the difference in latency (CL11 vs CL9)?

1) "The frequency of RAM is measured in megahertz and indicates the amount of data that can be moved to the memory stick at a time."

2) "Latency has more impact. Latency measures the delay before the RAM can achieve a specific task, and is displayed by a group of four timings, such as 6-8-7-12. In each case, the lower the number, the faster the performance."

So taking those two into account when putting a higher frequency memory (which of course has higher latency) on a lower frequency motherboard (which will limit the memory to work at this lower frequency), basically results in a poorer result.

However, you are probably right, that 2 ns cannot contribute to a noticable difference.

(All this was just me wondering why my Macbook works slower and heats so much. May be I should focus somewhere else, like changing the thermal paste of the CPU and GPU.)