Why I've Been Wrong

[ebarone]

For a while now I've been saying that as far as memory goes, having a high frequency is better than having tight timings, and by extension using different dividers has little to no impact. This isnt entirely true.. but its not what you all may think.

 

The Clock Crossing Procedure

I dont believe very many people on this site know much about a timing called tRD, the MCH Read Delay timing. This isnt a real memory timing persay, its more of a timing internal to the Northbridge, but its a critical timing number in the whole memory subsystem. In fact it makes the tCL-tRCD-tRP-tRAS settings look pale by comparison, and yet nobody ever seems to know to look there for performance enhancements. AFAIK it only applies to DDR2 memory, so all i7 users can (I think) ignore this. If anyone knows of an i7 setting along these lines, dont hesitate to speak up!

 

This is a very technical article explaining what exactly the tRD setting is, what it does, and where its used. I suggest everyone who thinks they are past "noob" status to at least try to read through it. Page 7 has some excellent real world performance result graphs, and page 9 is where you'll want to go if you want to skip to the end, but starting at page 4 will give you the whole story.

 

As it turns out, there are quite a few different configurations of memory dividers and FSB that will optimize performance. Its all dependent on your chosen FSB speed, and while 1:1 is sometimes the winner, this is NOT always the case. The one constant is the fact that the lower your tRD setting is, the better performance you'll see in your system.

 

Changing the tRD Value

I personally own a Gigabyte motherboard, and can only for sure tell you how to change this setting on another Gigabyte. However, this setting isnt called different things by different people, so it shouldnt be too hard to find on other brand boards.

 

On the Gigabyte, theres 2 ways to change it. The first is by changing the Performance Enhance setting, however this method is very limited. Standard for DDR2 is 12, Turbo is 6, and Extreme I believe is 4.

 

The other way, which is how I recommend doing it, is to look inside the memory settings. Down the long list of different settings that nobody knows what they do, you will find a setting called Static tRead Value. Thats the tRD, and setting that number manually will override your Performance Enhance setting. You can change it to any number you want from there.

 

On a non-Gigabyte board, I have no idea, maybe someone else knows. Look inside the advanced memory timings section of your BIOS, and look for something called Performance Level, tRead Value, tRD, or anything to do with the memory control hub (MCH), like MCH Read Delay.

 

!!!!Warning!!!!!

As with overclocking any other component of your system, fine tuning your tRD value doesnt come free. You will need to bump up your MCH voltage and possibly your Northbridge Voltage in order to tighten your tRD timing significantly.

 

Also, before changing this setting, make sure you know where your CMOS reset jumper is. Setting the tRD value too low can cause your system to not even POST, in which case a hard reset of your CMOS will be required.

 

I hope everyone can learn much from the Ananadtech article I posted above, and hopefully we can see some much improved benchmarking Keep reaching for the skies!

[IVIYTH0S]

that's really cool dude, I did notice a performance increase moving from "Standard" to "Turbo" memory mode. I'll have to try Extreme or manually set the tRD to 5 or something. I'll read that article too! Good post! :thumbs-up:

[hardnrg]

this is more commonly known as the Performance Level (as you mentioned), and is already widely documented and discussed, on this forum and others

 

good to know you've discoved the magic of subtimings (and manually setting them) and have shared the knowledge with the link

 

it's the first subtiming I adjust, shortly before tRFC

[ebarone]

I've only been really using these forums for like a month or so, and I've never seen anyone mention it. Is there a thread for all the other subtimings? I really want to learn as much about them as I can

[redtigerdragon]

I've only been really using these forums for like a month or so, and I've never seen anyone mention it. Is there a thread for all the other subtimings? I really want to learn as much about them as I can

 

someone posted this link that helped me...

http://www.hardwaresecrets.com/article/26/1

[IVIYTH0S]

the sub timings aren't more important than the main timings right? I mean i saw more of a performance boost running 5-5-5-15 and turbo mode, then running 5-4-4-12 with standard.

[ebarone]

Thanks red, but I meant the sub-timings, not the main ones. I've never seen a guide on those weird ones that are underneath the main CAS-etc-etc timings. And Iviy, from what I understand, the tRD timing is much more important than the main 5-5-5-whatever timings, since its the number that dictates how long before data can be tranferred between the two clocking domains. IMO, tuning tRD timing should be stressed more than the main memory timings, thats why I made this thread... I get the vibe nobody knows what the tRD actually is

[dr_bowtie]

the sub timings aren't more important than the main timings right? I mean i saw more of a performance boost running 5-5-5-15 and turbo mode, then running 5-4-4-12 with standard.

 

 

Depends what platform you run...for me neither AMD or Intel perform better with tighter timings than higher MHZ...

 

higher MHZ wins hands down every time...

 

and the same MHZ tighter main timings (CAS) results are very minimal in benchies and nothing in real world...

 

Subtimings are more important in DDR2 ram...

 

 

TRC, TRFC and TRD are the main ones to keep in mind....TRFC is the 1st timing I set is and AMD ddr2 rig...that is the memory slot frequency...too tight and the memory control works to hard and it wont clock or pass stress test...too loose and ram performance drops off quickly....

[ebarone]

Whats the performance impact of tRFC?

[Praz]

AFAIK it only applies to DDR2 memory, so all i7 users can (I think) ignore this. If anyone knows of an i7 setting along these lines, dont hesitate to speak up!

tRD does not apply to i7 based systems. However, these settings do apply to DDR3 when used with the X48 or P45 chipset.

[dr_bowtie]

Whats the performance impact of tRFC?

 

the looser it is the less ram bandwidth you have...too tight and it either wont post or it wont pass stress test...

 

I have had some set it too tight on high clocks and scramble the bios...needing a hotflash or a pre-flashed chip...

[Waco]

It all comes down to what gets you the bandwidth you need at a latency that's tolerable. "Looser" timings really aren't "loose" when you're running faster clock rates. CAS 2.5 at 200 MHz (DDR-400) is the same as CAS 5 at 400 MHz (DDR2-800) which is also pretty much the same thing as CAS 10 at 800 MHz (DDR3-1600), in terms of latency at least.

 

In the end it really makes little difference in gaming performance although you can gain a few percent in overall speed if you spend a few hours tweaking your memory timings.