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 Post subject: RAM Questions (Old School)
PostPosted: Thu Jan 24, 2013 8:42 pm 
8086
8086

Joined: Sun Jun 10, 2012 12:23 pm
Posts: 50
I have an old Core 2 Duo machine running with DDR2 RAM. I needed the computer for something, and that need has passed and I'm trying to find some use for it. Turns out, despite 5+ year old tech, it can play Borderlands 2 better than a 360.

The FSB speed is 800 Mhz, yet Intel won't allow RAM to run @ 800 Mhz as that would, for some reason, "overclock the processor". I've managed to get the machine to work by putting 667 Mhz DDR2 in the primary slot and 800 Mhz (I only have one stick of 667) in the secondary slot. The latencies listed on the 800 Mhz stick are higher than those of the 667 native stick. I'm hoping that the system has the 800 Mhz RAM at the lower latencies of the 667 stick as it is also running at 667. CPU-Z claims that the overall memory is humming along with 5-5-5-15 timings, though the "in detail" readout in that program shows results that make me wonder.

Would I be able to eke out better memory performance from this ancient machine if I were to put 2 identical sticks of 667 Mhz native RAM in it?


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 Post subject: Re: RAM Questions (Old School)
PostPosted: Thu Jan 24, 2013 10:30 pm 
Smithfield
Smithfield

Joined: Sun Jun 18, 2006 7:37 pm
Posts: 5530
Don't look at CAS latency as a number that means something by itself. It doesn't. CAS latency in clock cycles it takes to do the CAS step in RAM. Just because the number is higher, doesn't mean performance suffers. For instance, let's take a look at DDR2-667 @ 4-4-4-12 and DDR2-800 @ 5-5-5-15. And for fun, DDR3-1600 @ 8-8-8-24.

The total latency for these is:
  • DDR2-667: 6ns - 6ns - 6ns - 18ns
  • DDR2-800: 6.25ns - 6.25ns - 6.25ns - 18.75ns
  • DDR3-1600: 5ns - 5ns - 5ns - 15ns

So while yes, DDR2-800 has slightly longer delay than DDR2-667, it's an insignificant performance impact.

Although I'm just going to say to hell with all that. To be honest, I've not really seen a performance impact between DDR2-667 and DDR2-1066. So get whatever you can and what works with your system.


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