Regarding Ram Speed and Memory Controllers

[1yR4jE8b]

I'm having an argument with a friend of mine, and I could use some 'expert' opinions.

Me: "Today I learned that overclocking ram is pointless unless you're overclocking your processor too because a Sandybridge memory controller is only 1333mhz"

Him: "I'm running my ram at 2gHz and it's awesome, I have way more experience than you in this stuff"

Me: "I don't know man, the numbers make sense to me"

*ad nauseum*

I didn't really do too well in my Computer Org. class in University, (bout 71), so I'm a little fuzzy on minor details...but something doesn't add up about my friend's "experience".

[Disch]

I'm not an expert, but what I do know is that there's the bottleneck effect where the machine only runs as fast as the slowest related component.


My understanding is that the bus speed is usually the bottleneck in instances like this. It doesn't matter how fast your RAM is if things can only go across the bus at a slow speed.

[chrisname]

You're right. There wouldn't be any difference if you ran RAM at a higher speed than the CPU can access it; any effect he is noticing is a placebo. And he has additional heat & power usag edue to the higher speed that the RAM is running at, and if his PSU isn't powerful enough, the computer won't get enough power and will slow down as a whole...

Also, with RAM that fast he likely has poor timings, so it's probably faster to drop the (effective) speed to 1,333 MHz and set the timings lower. Changing the CPU to have a low multiplier and a high FSB speed would also be faster than just overclocking the memory; overclocking the FSB generally makes the system as a whole run faster, even if the effective clock speed stays the same (400x8 MHz < 800x4 MHz even though in both cases the clock speed is 3,200 MHz).

[1yR4jE8b]

So if I'm planning on upgrading to Ivybridge when they come out, they apparently have a 1600mhz memory controller, and I have *no interest at all* in overclocking, then I should just buy 1600mhz ram and save myself some money

I've seen 2200mHz kits that sell for 600$, yikes!

[z05DSL3A]

I thought that I read somewhere that the memory for Sandy bridge could be set to
800MHz, 1333MHz, 1600MHz, 1866MHz, 2133MHz, or 2400MHz via bios and it was independent of CPU/FSB speeds, set and forget. I think there is some jiggery-pokery needed for the two top speeds.

[chrisname]

I don't know much about Sandy Bridge tbh, that could be true.

[1yR4jE8b]

That's an interesting tidbit about Sandybridge, I'll look into that further.

As far as my friend goes, he uses an older i7 Bloomfield on the 1366 socket so I'm guessing he's just blowing hot air about OVERCLOCKED RAM IS SO AWESOME.

[zb0S216C]

For best performance, it's recommended that your memory speed matches that of your front side bus.

darkestfright wrote:

OVERCLOCKED RAM IS SO AWESOME

True, only if your CPU can match the speed. If your memory is too fast, the CPU will not be able to keep up, resulting in a performance bottleneck. Another factor is your main board( motherboard ). Some main boards can only handle a certain range of memory frequencies.

Only if they made serial front side buses. Still, front side buses are being replaced with the much faster Quick Path Interconnect.

Edit:

darkestfright wrote:

he uses an older i7 Bloomfield

I would preferably go for the hexa-core Intel i7x.

[helios]

If your memory is too fast, the CPU will not be able to keep up

Which is of course impossible, since the CPU is usually over 5 times faster than the FSB.

[zb0S216C]

helios wrote:

Which is of course impossible, since the CPU is usually over 5 times faster than the FSB.

My bad. What I meant to say was: If the memory's clock is faster than that of the front side bus, the memory will be outputting more data than the front side can handle, resulting in a bottleneck.

By the way, where did 5 come from? Are you referring to the bus/core ratio?

[1yR4jE8b]

http://www.legitreviews.com/article/613/1/

Found this, my friend uses XMP to overclock his ram. And this helped me understand alot. He doesn't overclock his processor, but XMP will overclock your ram and automatically adjust your FSB, vdimm, vcore etc...

[helios]

By the way, where did 5 come from? Are you referring to the bus/core ratio?

I was talking about the CPU multiplier. So, yes.

[chrisname]

@Framework,
He's referring to the multiplier (I mentioned it in my post). Clock speed = FSB x multiplier. Multiplier is usually more than x5. Often you can't change the FSB speed, in which case an overclocking-friendly CPU will be "multiplier-unlocked" (you can change the multiplier). Say a CPU has a stock multiplier of 8 and a locked FSB speed of 200 MHz. 200 MHz * 8 = 1.6 GHz. If you set the multiplier to 10, you get a clock speed of 2 GHz. If you set the multiplier to 5 and the FSB to 400 MHz, you still get 2 GHz, but generally, since the FSB is the bus that leads to the north bridge (memory controller hub), a high FSB speed will usually yield better performance than a high multiplier.

Edit: Nevermind, he got there first...

[Computergeek01]

Sorry about brining a two day old thread back to life, but I am a bit of an expert on this subject.

The number indicated by the CPU to be the FSB or Front Side Bus is not something the CPU itself sets (unless it's locked). It is what that unit is promissed to run on and rarely actually indicates what the processor is capable of handling.

Because of those pesky "Laws of Supply and Demand" often times CPU manufactorers will artificially decrease the supply of higher end processors so that they can actually sell their lower end fabs. They do this by setting the stock FSB or Multiplyer on "excess units" to what ever the lower end set of processors in that family can handle and since as chrisname pointed out ClockSpeed = FSB * Multiplier this brings the performance of the otherwise higher end processor down. Overclocking was origionally when geeks took advantage of this Supply trick and spent less money for the lower end processor because they believed they could get top shelf performance out of it by forcing those attributes back to what they can actually handle.

Overclocking the bus on a system overclocks everything on that line. Since this generally refers to speeding up the processor that line would be the North Bridge which includes the Processor, Video Card and the Memory with the Motherboard as the common link between them. You need to be aware of this since increasing the frequency to any device will generate more heat from it, so don't do it if you cheaped out and bought that video card that comes overclocked out of the box, or if any enviromental variable has your computer already running hot.

Regarding memory timings, unless you're using some half-assed utility that I'm not aware of these come stock on the Motherboard or else are set by the user. You bump the timings down when increasing the speed on the FSB has increased the system performance but also caused the unit to become unstable (periodic crashing) and diagnostics point to the memory as the point of failure. Decreasing the memory timing is in effect a way to decrease the speed, and therefore also decrease the strain, on the memory without having to decrease the speed on the rest of the FSB. Although as you can imagine this decreases the over all performance of the system it is a way of fine tuning it to get that extra ounce of performance out of your hardware.

It's worth mentioning that another way to improve system performance is to gradually increase the voltage to that device, however this increases heat generation logrithmically and so should only be done after you've confirmed, by stress testing the system, that your devices are all still running in side their heat spec.

There are so many factors involved in this, I remeber when it actually used to be a science. It was my first experiance truley Hacking anything. Now with all of the utilities, tools and stuff any idiot could figure out how to overclock a system inside of 10 mins, what a shame. For those of you who still think it's a science let me ask you this: When was the last time you had to physically bend a pin to ground on your processor to unlock the Front Side Bus?

[zb0S216C]

In addition to Computergeek's post, the speed of the memory not only depends on the frequency which it's running at, but also the latency.

Sure, an over-clocked CPU is fast, but the size of the Level-2 cache also determines the level performance. Most modern main-boards now have an integrated Level-3 cache which has a BSB( back side bus ) to access it( which is faster than the front side bus ).