Solved Kyle's thread of RAM noobage

[OneSerious]

Hello there Seven Forums.

Since I started trying to build systems a year or so back I keep on learning more and more about them everyday, which is great. However ever, every now and then I come across something that is probably considered "basic" that I realise I'm not up to scratch on and I feel like a bit of spanner.

A friend of mine is upgrading his system and asked me for a bit of advice. He asked me about RAM and so of I went to find him the best stuff... In doing this I found out I had made the wrong decision when selecting my own memory. So I looked around the net, read up in my Mobo manual and as above, I know feel like a bit of a tool.

When buying my RAM I went for Corsair XMS3 DDR3 PC3-12800 1600MHz because it was Corsair and also the highest frequenzy the store sold. My mobo can support up to 1866MHz so I thought it was a safe bet. However, I never took in to consideration what my CPU could support, which as it turns it is only 1333MHz. When I looked at my system and it reports that the RAM is running at 1333MHz.

Now come the questions...

1. Is it perfectly safe for me to be using 1600MHz in my system when the CPU only supports 1333MHz? It has worked okay thus far, and I assume the system only uses what it can, but I just want to know for sure.

2. In the attached image shows various memory timings and frequencies. Is there anything I can edit in the BIOS to get the most out of my RAM? ie change frequency and speed.

3. I assume since the timing is labelled as "latency" then the smaller the number the faster the memory?

These probably all sound like very simple questions, I just can't believe I never came across this before now.

cheers in advance for any help guys!

 

[1Bowtie]

First for question #1 yes as long as it's running stable. #2 from what i'm seeing in pic is your running at max timings for your cpu and motherboard spec's. #3 your motherboard and cpu supports 668mhz which is 1333 mhz dual channel, when you start messing around with timings and voltage's you really need to know what your doing because you can render your comp unuseable with the slightest change so be careful what you wish for. Stable and running smooth is GOOD

 

[OneSerious]

First for question #1 yes as long as it's running stable. #2 from what i'm seeing in pic is your running at max timings for your cpu and motherboard spec's. #3 your motherboard and cpu supports 668mhz which is 1333 mhz dual channel, when you start messing around with timings and voltage's you really need to know what your doing because you can render your comp unuseable with the slightest change so be careful what you wish for. Stable and running smooth is GOOD

If looking at the pic you think the timings are fine then I'm happy. Since I'm not in the know, I would have been willing to change stuff had it of been worth while. The system is running smooth so I'm happy enough.

Am I right in saying that when it comes to timing lower numbers are better? For example 7-7-7-20 is faster than 9-9-9-24.

 

[chev65]

Ok on the CPU only supports 1333Mhz BS, that is just the Intel imposed limit which in reality is much much higher than what Intel claims. They also claim that their CPU's don't support overclocking which as we all know is not true.

They just do that to protect their CPU as the memory controller is now on the CPU. You can easily and safely go much higher and contrary to what Intel says their CPU's do indeed work with higher Mhz memory, 1333-2000MHz+.

And yes tighter timings are faster but it gets to a point where it won't be stable anymore.

 

[OneSerious]

Ok on the CPU only supports 1333Mhz BS, that is just the Intel imposed limit which in reality is much much higher than what Intel claims. They also claim that their CPU's don't support overclocking which as we all know is not true.

They just do that to protect their CPU as the memory controller is now on the CPU. You can easily and safely go much higher and contrary to what Intel says their CPU's do indeed work with higher Mhz memory, 1333-2000MHz+.

And yes tighter timings are faster but it gets to a point where it won't be stable anymore.

Well the only thing there is is that my CPU is an AMD. Would you say the same applies to them?

 

[Lordbob75]

Add me on the list of having no idea as to the relation of CPU to RAM.

I know there is a relationship between the two, I just don't know how it works.

~Lordbob

 

[whs]

First for question #1 yes as long as it's running stable. #2 from what i'm seeing in pic is your running at max timings for your cpu and motherboard spec's. #3 your motherboard and cpu supports 668mhz which is 1333 mhz dual channel, when you start messing around with timings and voltage's you really need to know what your doing because you can render your comp unuseable with the slightest change so be careful what you wish for. Stable and running smooth is GOOD

If looking at the pic you think the timings are fine then I'm happy. Since I'm not in the know, I would have been willing to change stuff had it of been worth while. The system is running smooth so I'm happy enough.

Am I right in saying that when it comes to timing lower numbers are better? For example 7-7-7-20 is faster than 9-9-9-24.

That is correct - the lower the latency, the better. It is especially the first number (CAS latency) that counts. 9 at 667MHz is rather high. I think there are Dimms with a CAS latency of 6 at 667.

PS: if you want to educate yourself on the matter, there are several excellent (e.g. Wikipedia) entries on the web.

 

[Everlong]

Higher latencies mean slower RAM in the sense that as you raise the timings, especially CAS, you delay more clock cycles, thus increasing the latency in nanoseconds.

For arguments sake, take a typical CPU at 3GHz, and RAM with a raw latency at 5ns (don't bring the CAS in to the equation). Now the CPU is doing 3 billion cycles a second and wants to access the RAM. In that 5ns the CPU has already wasted 4 complete cycles from the first cycle where it wanted to access the RAM, to actually accessing the RAM. Yea the RAM is the fastest component in the PC in terms of bandwidth etc, but it's quite a big bottleneck in terms of how fast the CPU and RAM work together.

 

[GeneO]

I am not sure your motherboard will support this - some Asus do. You may be able to select timing profiles for your memory. The SPD interface to the memory allows the BIOS to detect memory profiles from the memory. Check your BIOS.

Yes the lower numbers are better. Those are the number of memory cycles needed to perform certain operations. The most important, CAS latency, is the number of clock cycles it takes to read out a column from memory. So 7 is 7 clock cycles.

You should be able to get the 6 or worst 7 CAS at that frequency (1333).

Gene

 

[OneSerious]

Add me on the list of having no idea as to the relation of CPU to RAM.

I know there is a relationship between the two, I just don't know how it works.

~Lordbob

Glad I'm not the only one.

That is correct - the lower the latency, the better. It is especially the first number (CAS latency) that counts. 9 at 667MHz is rather high. I think there are Dimms with a CAS latency of 6 at 667.

PS: if you want to educate yourself on the matter, there are several excellent (e.g. Wikipedia) entries on the web.

Whilst 9 is the highest I've seen would you consider it bad? I have no intentions of changing the RAM now because I don't have the money or anybody to take the old sticks off me, but I use the system for gaming and it seems adequate. Do you think faster RAM would make much of an impact on performance?

Higher latencies mean slower RAM in the sense that as you raise the timings, especially CAS, you delay more clock cycles, thus increasing the latency in nanoseconds.

For arguments sake, take a typical CPU at 3GHz, and RAM with a raw latency at 5ns (don't bring the CAS in to the equation). Now the CPU is doing 3 billion cycles a second and wants to access the RAM. In that 5ns the CPU has already wasted 4 complete cycles from the first cycle where it wanted to access the RAM, to actually accessing the RAM. Yea the RAM is the fastest component in the PC in terms of bandwidth etc, but it's quite a big bottleneck in terms of how fast the CPU and RAM work together.

So in my case the CPU wastes 8 cycles before it accesses the RAM? I'm not asking for a full explanation here because I could probably keep you going all day about it, so I'll try and read up myself. But long story short, since we are talking about nanoseconds, how big an impact does that have on a systems performance running games for example? Since I'm not in the know I can't say, but I imagine because of the time frames we are covering here it couldn't be much.

Thanks for the help thus far guys.

 

[whs]

To a certain extent the discussion is a bit academic - agreed. Since you are where you are and stuck with those Dimms, I would not really worry about it. As with many of those performance numbers, they are nice to know, but in real life they may not make a big difference. The main thing is that you are happy with your system and its performance. If you are able to settle with what you have, you made a big step forward.

 

[Everlong]

Yea what I said is going kinda too far in to it all, and doesn't really matter as it's negligible for just general computer usage, unless you need precision to the nanosecond.

 

[GeneO]

As a real-time programmer I knew oft said (though it was in microseconds instead of nanoseconds):

A nanosecond here, a nanosecond there, pretty soon you have real-time!

Seriously though, between 9 and 7 at the same frequency you are talking 29% difference, though it will not translate into that much in reality.

- Gene

 

[Everlong]

As a real-time programmer I knew oft said (though it was in microseconds instead of nanoseconds):

A nanosecond here, a nanosecond there, pretty soon you have real-time!

Seriously though, between 9 and 7 at the same frequency you are talking 29% difference, though it will not translate into that much in reality.

- Gene

Real time computing will come when computers are photonic. Computer scientists kid themselves about instantaneous computing at the moment just to help them sleep at night

 

[OneSerious]

Cheers folks! I think my RAM understanding is where it needs to be without getting down to the real nitty gritty. It is funny how these things pass you by, but now I know.

Thanks again.

 

[1Bowtie]

Glad your satisfied with what you learned and as long as your computer is stable and playing your games the way you want, it's all good.