Latencies vs. FSB

{AG}Sgt.Stryker · Feb 8, 2005

After reading all the debate about latencies vs. FSB, I decided to experiment. On my machine (see sig), I found that increasing latencies from 2-2-2-5 to 3-3-3-7 caused only a 1.7% decrease in memory bandwidth at the same FSB (200). However, increasing the latencies allowed me to go from 200 to 240 FSB, which yielded a 20% increase in memory bandwidth (with the CPU multiplier backed off to keep it at a comparable speed). I have bitmaps of the benchies if anyone wants to see them. I don't know how to post them.

So I guess the conclusion is, if you can gain at least a 2% increase in FSB by backing off your latencies a notch, then it's worth it.

Sorry if this is a "DUH!" to the old hats, but as a relative noob I thought it was interesting.

dropadrop · Feb 9, 2005

It would probably be best to try some "real world" applications and see how much the differance is. Loosening up the timings does not necassarily do so much "harm" to bandwidth, but it does add latency which can slow down programs.

There has been alot of tests, and aparently the differance is not huge in all applications, but it is in some.

But now that we have a good thread title, I have a question... How big is the performance differance between 1T and 2T with a socket 939 A64? With 1T my ram will run at about 240fsb, with 2T I seem to be stable atleast 260fsb (have not had time to try higher yet).

NinjaZX6R · Feb 9, 2005

This seems like a never-ending experiment.

OK, so it is true that timings do VERY little to help memory bandwidth at any given clock speed, but that is not where the performance boost comes from. Run a test of 3d Mark 2001 with 3-3-3-8 and then 2-2-2-5. It will probably be good for around 500 points at least. It is on my rig anyway.

As for 1t or 2t....I saw about 250 more points in 01 with running 1t. It DOES help, but yes, it also hinders your overclock. There are other programs that will suffer even more than 3d mark with 2t timings. I can run all the way up to like 300mhz HTT speed on mine at 2t, but I'd still rather have 1t at around 260HTT....It just isn't worth the overclock if I have to use 2t. I'm sure some others will disagree...but to each is own.

-Collin-

Rumrunner · Feb 9, 2005

{AG}Sgt.Stryker said:
On my machine (see sig), I found that increasing latencies from 2-2-2-5 to 3-3-3-7 caused only a 1.7% decrease in memory bandwidth at the same FSB (200).

Actually, thats pretty remarkable.

Foxie3a · Feb 9, 2005

In benches I see about a 200mb/s difference going from best to worse latency.

For some reason 2-2-2 seems real "snappy" in windows when you start getting over 200 FSB. I've done like 210FSB 2-2-2 and windows did things quickly. But I would definately rather have 240FSB at 2.5-3-3 over 210FSB, that extra 500mhz is much better than a wasted RAM clocks.

Those are only my experiences though.

{AG}Sgt.Stryker · Feb 9, 2005

What I'm most interested in is game performance. What's better, low latency or high bandwidth? My non-scientifical thinking is, high bandwidth is good. Mo bits, mo betta! But some folks apparently think quicker bits, mo betta. So I guess the question is, when you're pushing the envelope, do you go for more bits (high bandwidth), or faster bits (low latency)?

Foxie3a · Feb 10, 2005

FSB is better in pretty much everything I'd say. Lower latency seems to work better with Athlons and FSB seems to work better with P4's.

You have a 3.8ghz P4 with RAM at 3-3-3, and you're worrying about latency. It looks like you love games, so I would recommend putting all of this effort into looking into a better Vcard. I dont know what a 9550 is exactly, but the **50's are crappy for ATI and good for Nvidia, so I can only guess it's a worse than 9500 or pro.

{AG}Sgt.Stryker · Feb 10, 2005

Foxie3a said:
I would recommend putting all of this effort into looking into a better Vcard. I dont know what a 9550 is exactly, but the **50's are crappy for ATI and good for Nvidia, so I can only guess it's a worse than 9500 or pro.

Funny you should say this. I just ordered a BFG GF6800 Ultra OC, thinking the 9550 was a bottleneck. I picked up the 9550 for cheap in a clearance sale and didn't research it beforehand. It replaced a GF4600Ti and was only a slight improvement (about 500 3D Marks).

Great minds...!

TimoneX · Feb 10, 2005

Sandra doesn't show much of a dropoff with increased latency settings on the A64, but real world apps do in general. I posted these results I received a few days back, forgive me if you've seen them already. I think it makes it pretty clear that lower latency settings are more important than some would like you to believe. The results are all compared to 200x10@2-2-2-6 1T.

http://www.ocforums.com/showthread.php?t=364207

{AG}Sgt.Stryker · Feb 10, 2005

Hey thanks, Timo. I had seen the start of that thread but I hadn't been back since you posted the results. Very interesting!

TimoneX · Feb 10, 2005

TY and I've been adding to the discussion as I analyze the results further and add to them so make sure you check back.

Lifthanger · Feb 10, 2005

this article is a very interesting read : link

it was done with an A64 system s939.

bottom line pc3000 at 2-2-2 is not much slower than pc4700 3-4-3, while pc 3500 2.5-2-2 is even faster.

My personal conlusion: A64 with dual channel isn't able to make use of more bandwidth at a certain point. My coming A64 system will be mounted with cheap twinmos speed premium that will probably run between 225 and 240 MHz 2-2-2..
Sandra bandwidth is nice, but has no real use for real world performance.
I personally don't get the drooling about >9000MB/s , when 6000MB/s at tighter timings produce higher fps.

TimoneX · Feb 10, 2005

Agreed. Now if I could just locate someone guaranteeing winbond UTT on TMSP 512Mb modules.

NinjaZX6R · Feb 10, 2005

TimoneX said:
Agreed. Now if I could just locate someone guaranteeing winbond UTT on TMSP 512Mb modules.

My cousin just ordered the Speed premiums from newegg. He got the one gb kit for $140. I will let you know if they have the UTT chips. I think it is pretty likely they will, since that is all twinmos is using now. So, unless you get an older set, it's a good chance!

-Collin-

TimoneX · Feb 10, 2005

Got some TMSP on Tues that was PSC. VILE performers. I'll probably have another go at it though. One more set of duds and I'll just go with OCZ voltage extreme. Yeah lemme know. That's the TMII kit? Lemme know what speed rating the chips are too if you'd be so kind.

Lifthanger · Feb 10, 2005

If you're from germany: cheeep

they're advertising TMSP with winbond chips. 150€ for 1GB this is 80€ less than VX.

They should arrive 'til monday and I'll tell you what they are able to do. (with 3V max of course

)

NinjaZX6R · Feb 10, 2005

TimoneX said:
Got some TMSP on Tues that was PSC. VILE performers. I'll probably have another go at it though. One more set of duds and I'll just go with OCZ voltage extreme. Yeah lemme know. That's the TMII kit? Lemme know what speed rating the chips are too if you'd be so kind.

Oh CRAP! That is probably what my cousin is going to end up with! And here I am making him get a booster!

-Collin-

Latencies vs. FSB

{AG}Sgt.Stryker

Member

dropadrop

Member

NinjaZX6R

RAM Junkie

Rumrunner

Member

Foxie3a

Normal Member

{AG}Sgt.Stryker

Member

Foxie3a

Normal Member

{AG}Sgt.Stryker

Member

TimoneX

Closet Elitist Member

{AG}Sgt.Stryker

Member

TimoneX

Closet Elitist Member

Lifthanger

Member

TimoneX

Closet Elitist Member

NinjaZX6R

RAM Junkie

TimoneX

Closet Elitist Member

Lifthanger

Member

NinjaZX6R

RAM Junkie

Similar threads