I've been thinking about a new build around an i5 3570K and a Z77 motherboard (ASUS or Gigabyte). Looking at memory I see 1.65 v and 1.5 v. Looking around the internet I see both opinoins: "Does not matter" and "Can not use 1.65 v because it does not meet spec". Any opinions?
Bob, my understanding is that the memory voltage can be safely raised to 1.65V (most motherboards support even higher voltages). However, 1.5V memory is preferred for two reasons (in my opinion). The lower voltage results in slightly lower power and heat. It also gives more "headroom" to get better timings by raising the memory voltage, much like raising Vcore lets you overclock a CPU to a higher frequency.
Some manufacturers (I believe) take slower RAM and call it faster RAM by speccing it at a higher voltage (1.65 vs 1.5). For example, some RAM that is rated at 1333 @1.5V might be usable at 1600 @1.65V. If you want to run the RAM at 1600, it would be preferable to get RAM that is rated at 1600 @1.5V. If for some reason it's a little unstable at that speed, you have room to try raising the RAM voltage a little to see if it makes it stable.
Thanks for the feedback. Since I posted I came across this from a supposed Intel guy:http://communities.intel.com/thread/30798
He only recommends 1.5. I guess you can specify the memory voltage through the MB BIOS. But if the default is 1.5v and you don't raise it to 1.65 wouldn't the memory run slow?
I'm thinking I'll stick to 1.5v.
Bob, if the speed is rated at 1.5V, theoretically that's all the voltage you'll need. If the speed is rated at 1.65V, you'll already be at the recommended maximum for the chipset. I agree with you, try to stick with the 1.5V memory.
1.5V is the standard memory voltage. Memory controllers are fairly flexible and will be able to handle 1.65V just fine as well. 1.65V allows for memory to run at higher frequencies or lower latencies. However, these things have almost no measurable effect on overall performance, so there's very little point to using 1.65V memory.
So just stick with 1.5V, which is the official specification and saves you some power (though it's very little, well below 1W).
In a word? No. Using 1.5v vs 1.65v makes no difference unless you are overclocking RAM (to increase RAM frequency) or underclocking RAM (to tighten RAM timings) - else it makes no difference whatsoever - and doing even those things really doesn't do hardly anything as far as increasing overall system performance except maybe squeezing 2-3 extra frames per second for gaming, or for bragging rights, or benchmarking. You'd be way better off just getting a better graphics card instead.
What is more critical is to test each individual RAM stick using MEMTEST86 as soon as you get it and return the RAM if any one of them has errors which is all too common and overlooked by far too many system builders. The bit about using only 1.5v on Intel boards is a wives tale - pure bunk. I totally ignore it and have for years been using 1.65v RAM on my Intel motherboards, and I heavily overclock my CPUs as well with no ill effects.
When picking motherboards however, I do prefer my newer X79 boards in that I can set my RAM to XMP mode and forget it. I can overclock the CPU without impacting any other components, including my RAM - compared to my old i7 920 P6T where I also overclocked using XMP but had to muck with the RAM parameters a bit since I could only use the base clock (BCLK) to push the CPU as opposed to using just the CPU multiplier as I can on the newer chipsets and BIOSs.
As for future-proofing, that is about as good as future proofing motherboards - it rarely does. Next up will be Quad-channel DDR4 RAM with a dedicated channel for each individual RAM stick (instead of one channel per RAM pair). Worth it? Probably only for high end servers and big databases.
I'm not enrirely sure what all this means but from Kingston's spec sheet for a HyperX Red KHX16C9B1R/4 4GB Memory Module:
"This module has been tested to run at DDR3-1600 at a low latency timing of 9-9-9 at 1.65V. The SPD is programmed to JEDEC standard latency DDR3-1333 timing of 9-9-9 at 1.5V. This 240-pin DIMM uses gold contact fingers and requires +1.5V."
So, Bob Collette got it right. It looks like they up the standard voltage to get the higher speed.
Yep, it is 1333 RAM @ 1.5 that you can overclock to 1600 with CAS 9 timing. I'd stick with native 1600 @ 1.5v or 1.65v - there are a ton of options out there: