[Solved] 1333 ram running at 1280

I have oc'ed my i5 750 using 160 base clock and i had to use x8 ram multiplier to run the ram at 1280 which was the closest to 1333. Am i losing any performance by doing that? Can this ram run at 1600mhz? Will i see any noticable performance gain if i run this ram at 1600mhz? The ram kit is this :
KINGSTON KHX1333C7D3K2/4GX DDR3 4GB (2X2GB) PC10666 1333MHZ HYPERX DUAL CHANNEL KIT

No. You'll not notice a decrease in performance, and I doubt your RAM would run at 1600Mhz with C7 timings.

I know it won't run at C7 probably will run at 8-8-8-24. That was the question about, should i go the extra mile and try that RAM at 1600 or stick with 1280 as i am right now. I am more interested in FPS gain so if anyone knows from experience the gain or not please reply.

EDIT : Also since i am running below 1333mhz (-53mhz to 1280) can i try tightening the timinings or 7-7-7-20 are already too tight?

Yes but RAM timings and Mhz both have a direct effect on RAM performance, so If you up the Mhz to 1600, but in order to do so you have to increase the timings then your not really gaining performance.
Increasing the RAM speed from 1280 to 1600Mhz even if you managed to keep C7 timings (perhaps by upping the DRAM voltage) wouldn't result in much performance gain at all in terms of FPS, maybe by 0-1%
My brother was recently testing this out for himself, he was trying to justify his £170 2000Mhz RAM, he tested the RAM at 1600Mhz C8 and then at 2000Mhz C8 and found almost unmeasureable performance gains.
If your looking to up your FPS in games then your wasting your time trying to up RAM Mhz or tighten Timings, its just not worth your time and effort.

Even though I know tightening the timings won't make hardly any difference at all, I still did it, I also have 1333Mhz RAM, mine is rated at 8-8-8-24 1.65V
I've managed to run it at 1230Mhz at 6-8-6-18 1.68V, However this is only possible due to the fact I upped the DRAM voltage, leaving the DRAM voltage at 1.65V results in instability at those timings.
You can adjust each number individually, so for example you don't have to go from 7-7-7-21 to 6-6-6-18.
Its up to you whether or not you overvolt your RAM to achieve tighter timings, if you do, make sure you keep your QPI/VTT voltage no lower than 0.5V from your DRAM voltage, you could cause damage to your CPU if you do not follow this rule.

My QPI Voltage is 1.355V and my DRAM is 1.68V so I'm well within safe limits.

If I were you I'd try 6-7-7-20 first, run an hour of Intel burn test or blend mode on Prime95, if it all goes well try 6-6-7-20 and test again.... When it becomes unstable you have to decide whether to up the DRAM voltage to regain stability or to up the timings slightly.

Shouldn't it be .5 volts between the QPI and the DRAM Voltage? You have a difference of 0.325. I use 1,19 QPI/Vtt and 1.66 dram. Anyway so to tighten timings you need to up the voltage, i guess i won't be doing that. The RAM has an XMP profile which i don't use but when i first installed it and enabled it it set QPI/Vtt 1.21 and Dram voltage 1.66. So i am guessing since i am currently using 1.19 on QPI i could try lowering the voltage of the RAM to 1.64 or less.

I am a little confused. Isn't the goal to be as close to 0.5v as possible? Or is it the opposite? Lets say you have a 0.3v difference, is that safer than having 0.4v difference?

Update : now running the 1333 ram with BCLK 160 and x10 multiplier resulting to 1600mhz with 8-8-8-20. prime memtest and IBT all were stable

Yes it was a nice experience this OC. I guessed using 166 BCLK to run the ram at rated speed 1333 wasn't a good practice because when turbo kicked in i reached 4ghz which required more voltages. So upping the ram at 1600 with CL8 was a nice boost. I set the timings 8-8-8-20 and didnt change anything else. Should i type in the other settings also? They are on AUTO now. The difference from before when i had the ram 1280 at CL7 is the tRFC which was 72 and now is 88. What is that?