Setting the correct FSB X Multiplier

[Vijay]

I have an Asus a7v8x-x Mother Board with an AMD 2600+XP cpuand I have installed PC2100 256 X2 DDR ram.

The present setting are 12.5 Multiplier and 166/33 for the FSB.

Could you tell me if these are the optimal setting I can have with the present set up and also how I can overclock-and to what extent and yet not damage the Comp

Thanks

Vijay

[Austin]

Well first be careful as your RAM is only rated for 266mhz (PC2100) not the 333mhz (PC2700) you're currently running it at. Be sure it is stable, you can higher the RAM timings if it isn't. You have a KT400 mobo which a very decent performer, but like most non-nF2 you are almost certainly limited to 12.5x max multiplier. That leaves the FSB, KT400 were designed for 333FSB operation and use an automatic 1/5 divider to make the PCI/AGP/IDE run at the normal speed. You will likely find the BIOS allows you to go to 400FSB BUT that is NOT likely to work unless you magically have a 1/6 divider (as found on the KT600) needed for 400FSB. So you should find 360FSB (2x180 due to DDR FSB) the maximum as 36mhz is in spec for the PCI but some AGP or IDE devices may not like, even some PCI devices may not like 36mhz. As usual just go up in small steps testing thoroughly for stability at each setting. When you find your limits you may need to raise the CPU voltage (TbredB 1.70-1.75v absolute max IMHO) if you are 100% certain cooling is not the thign holding you back. You could find your cooling limiting but PC2100 is almost certainly the most liekly hinderance ... anyway XP2600+ is hardly bad eh?

[Vijay]

Thanks Austin,

If I read you right I should change the Ram to PC2700/3200.to improve on performance.With PC3200 what would be the max I could go to (theoretically that is?

Regards.

Vijay

[Kezzer]

a FSB speed of 400MHz overall with PC3200 RAM but then sometimes you can push it a little farther.

It all depends but PC3200 theoretically runs at 400MHz, mine does it fine.

[johnyhy1]

i am using a kt400 m/b and my ram will only run @ 333 and its 400fsb i think its something to do with my chip running @166fsb

[Vijay]

Thanks for the info.It seems I need to change the Ram and fix the FSB speeds accordingly.

One other point-could you guys please go through what is being reported by the Asus probe and tell me if I have cause to worry:-

CPU Temp 57C/34F
MB Temp 40C/104F
CPU Fan 4383
+12V 12.608
+5V 4.919
VCore 1.696

AMD CPU is supposed to run at 1.6V if I am not mistaken.

There is a difference in the tempratures reported in the CMOS and those by the probe , the former are about 10 degreesC higher.Which one should I trust?

[Austin]

When running at a FSB speed you should almost always run the RAM in sync (same speed), usually there's only an option to run the RAM faster NOT slower and the perf hit is usually large for slower ... and faster has minimal gains if any. So...

266FSB (2x133 due to DDR) you should use DDR266 (PC2100).
333FSB (2x166) you should use DDR333 (PC2700).
400FSB (2x200) you should use DDR400 (PC3200).

KT400 are not designed for 400FSB, just 333FSB max but you can o/c, 360FSB is the safest max speed. You should find PC2100 can actually run faster than 266mhz esp if you use slower (higher) RAM timings. Same goes for PC2700 going higher than 333mhz and PC3200 higher than 400mhz, since you're o/c'ing it there are no guarantees and you MUST ensure you are 100% stable if you run it faster than it's rated for. Exactly how fast a given spec RAM can run varies, buying a good brand like Crucial or TwinMOS is well worth it though. So I would suggest buying PC3200 as that is guaranteed up to 400mhz and although KT400 won't hit that reliably it does mean it won't limit your FSB o/c to around 360mhz.

The temps reported are a rough guide only, your mobo BIOS is the most accurate place to look closely followed by specific mobo sw, rem temps go up when your system starts doing stuff though. Generally AthlonXP dislike going above 60'C but as said the readings you get are VERY approximate more useful for monitoring the diffs in temp you get from a new case fan or HSF. The normal voltage for AthlonXP depends upon its core; 1.50v, 1.60v and 1.65v are usual and it's normal for the mobo to use slightly higher values to enhance stability and o/c'ing. 0.05v extra gives off a lot more heat, many CPUs can be undervolted, I run my BartonXP2500+ (1.8ghz) at 2.00ghz most days as I can undervolt it to 1.55v (from 1.65v) and run my £15 Volcano11+ at only 2200rpm. Your voltage rails usually fluctuate whatever you do, run or buy, if you're stable then you're stable so don't worry too much. IIRC 10% variance (5% either way) is perfectly within the operating specs.

[Vijay]

Thanks Austin,


"You should find PC2100 can actually run faster than 266mhz esp if you use slower (higher) RAM timings."

I am confused please could you explain what Slower (higher) ram timings are?


Vijay

[Austin]

The CL rating (Cas Latency) is usually quoted with the designed speed fo the RAM's (eg 333mhz for PC2700) but this and the numbers which (should) follow can be daunting.

RAM is effectively arranged in rows and columns (much like a spreadsheet) so then CAS is Column Address Strobe, RAS is Row Address Strobe. The RAS, CAS and the RAS-to-CAS latency are basically the time spent waiting to locate, read or write a given area of memory but if a consecutive block of memory is needed the significance of any latency is pretty minimal, so latency is of greatest importance when using memory randomly.

The problem is all that's often quoted about latency or RAM timings is the CL number, it's the most important but less than 1/5th of the story. If you line the timings all up you can state a more complete picture. You should get quoted CL2.0 as being 2-2-2-5 (but could also be 2-3-3-7) and CL2.5 as being 2.5-3-3-7. The 1st number is Cas Latency, 2nd RAS Precharge, 3rd RAS-CAS, 4th Act Precharge (IIRC). BIOS' may use diff notations but that's basicly the principle and lower is always faster as it means less waiting. Other things to look out for are Command: T1 (faster) or T2 (normal) and Bank Mode: off, 2 (fast) or 4 (faster). Anything to do with Memory holes, caches (not L1 or L2), shadowing and the like should be disabled. AGP Aperture is best at 256MB but there isn't (technically) really a perf hit in going lower, it's only assigned if the system has it free and your gfx card's own RAM 'runs out'.

As always there are many factors, CL2.0 is NOT 25% faster in real world performance, even when you isolate the RAM in a test. When you o/c, you can raise some of these 'latency' settings in order to run at a higher mhz. So you may prefer 2-3-3-7 400mhz over the default 2-2-2-5 333mhz for example.

These figures are based around KT333 type era but should still be accurate, if anything it's lower now as most of what Dual CHannel does is reduce latency esp on SktA. Anyway at the same clockspeed 2-2-2-5 is rougly 1.5% faster in Sandra's RAM Benchmark than 2.5-3-3-7. It does depend on what you do with the RAM as to the exact perf diff. Sysmark2000 shows a 4% improvement. Quake3 & 3Dmark2001 show 3% improvement. 2-3-3-7 gives pretty much the same perf as running 2.5-2-2-5.

If adding a new DIMM to an existing DIMM rem that the limit and timings are dictated by the slower DIMM. 256MB DDR333 CL2.0 coupled with 256MB DDR266 CL2.5 will both effectively be limited to DDR266 CL2.5. Cas Latency should be selectable in the BIOS, SPD is automatic, if you don't find many settings for latency then try the latest BIOS or CTRL+F1 in the BIOS on Gigabyte mobos.

I'm not saying any of the above is 100% definitive by any means, just what I've gathered from notes I've made coupled with experience.

So bottom line slower RAM timings relate to the higher numbers (more waiting) which you can find in your BIOS under 'Cas Latency', 'RAS-to-CAS' etc. It can be helpful for o/c'ing your RAM (and hence CPU, FSB etc) to use higher numbers and disable things like Bank=4 as although they increase perf a tiny amount they may hold back your system's o/c which should hold bigger gains anyway. The other popular way to make your RAM run at a higher mhz is to overvolt. Overvolting makes the internal signals stronger but seriously stresses your RAM a lot more and will produce a lot more heat too.

[Vijay]

Thanks Austin,

Thank you for the post.Will study it and, if I may, get back to you later after changing my Ram.

Regards,

Vijay

[shamus21]

austin you sure know your tech, do youu work in the computer business.

[Austin]

Originally posted by shamus21
austin you sure know your tech, do youu work in the computer business.

Ah that would be telling wouldn't it .... at the mo much of my time's spent looking after my wife and children and their medical needs. Nice to spend the time with them (and escape to the forums now and then)!

[Vijay]

Austin Sorry for the delayed reply but I was out of town and just got back. The ram is expected shortly and will post once it is.

Thanks Guys

Vijay

[Vijay]

Hi,

Just got the Pc2700 ram and installed it.

Haven't changed any settings and am running it at12.5x and the fsb at166/33.

The comp is noticeably faster and possibly there is no need to overclock it but will experiment over the next few days.

Thanks all for the help& advice,

Vijay

[Vijay]

Help,

See my post about Temps.Cant seem to figure out why it is running so hot compared to temps others MB show.

Any suggestions?

Vijay

[Austin]

Is it running stable? If so don't worry too much about the reported temps as they are a rough guide only esp when using Windows programs. If you are running hot then you should look at voltage, HSF, compound (too little, too much, poor quality etc), case ventilation and case airflow.