Don't trust "Auto" settings on memory!!

[aelfwyne]

I have 2 sticks of Patriot PC4000 DDR. Rated at 250mhz. Asus A8V, Opteron 170. I figured, "Okay, as long as I'm not overclocking the memory beyond 250mhz, then it should be okay at Auto, as that'll set it to whatever the SPD specifies, right?".. WRONG.

I kept having stability problems.... I was having to set dividers down extremely low, as pushing past 200mhz at all would cause a crash.

Turns out, that my motherboard's "Auto" settings were only setting SOME things according to the SPD... A couple of values weren't being set, as I discovered with A64Info and RightMark Memory Analyzer. Even though the SPD specified values for tRC and tRFC at 200 and 250mhz, the values my system was actually using with "Auto" were MUCH lower than had been specified by the SPD.

I bumped the values up to what is recommended by SPD, and while all my problems with memory haven't gone away (it still will not hit its rated 250mhz), it HAS become much more stable.

I still can't get the memory to go much over 200mhz - but with those values "fixed", my stability at 2.7ghz has become much better....

Now, if I could just figure out what voltage I'm actually running.... A64Info reports one thing, ASUS PC Probe reports something else (much higher!!!)... Since I doubt I'm doing 2.7ghz at 1.3v, I suspect the PC Probe is more accurate. Very annoying that A64Info was wrong, as I'd used it to set my voltage to 1.5, and apparently it was running at 1.7 according to PC Probe!

Anyway... those are my adventures... And a lesson - don't depend on a motherboard to even set the memory values according to the SPD.

 

[sygyzy]

What does SPD mean? The speed of the memory? How does that "recommend" settings? I am confused here.

 

[cmdrdredd]

basically setting SPD on the mobo will read the chips on your memory and set the timings by default according to whatever speed it's running at. Each memory stick is programmed with certain parameters as default, the mobo reads this and sets accordingly.

 

[Regalk]

But not every bios can read the programmed settings correctly especially the high end "o/clocked" ram - spd or auto settigs works most of the time but not always - OCZ was a good example of this in the past but things have changed for the most part and generally Auto or SPD (Serial Presence Detect) should work. Whenever ther is boot, cold boot or similar 9 times out of 10 it is Ram th eother being user error

 

[myocardia]

You never once mentioned any specific memory timings. Did you run that RAM at 3-4-4-8 @2.7v, when seeing how high it would go?

 

[dennilfloss]

Mine is set to auto.

 

[Stumps]

mine ain't...SPD timings are too slow for my likings

 

[aelfwyne]

Originally posted by: myocardia
You never once mentioned any specific memory timings. Did you run that RAM at 3-4-4-8 @2.7v, when seeing how high it would go?

3-4-4-8 is the rated timing for 250mhz on this memory, yes. I had tried that and it didn't work. It turns out that it wasn't setting the tRC or tRFC settings correctly. At 250, they should be around 13.75/17.5, and it had them both under 10. Settings those settings up, it was a little more stable, but not completely so...

I still have been unable to get the memory even close to 250mhz. I also tried 2.8volts which is the highest my board will go (Asus A8V)

 

[tempoct]

I just have totally opposite experience on this. Auto is fine on mine but manual setting cause me some memtest error.
SPD supposes to be stable at stock. One thing Auto might not set right is the mem voltage. I'm pretty sure that the timing will be more stable (read less aggressive) timing than your own.
My thread on the issue;
http://forums.anandtech.com/messageview.aspx?catid=28&threadid=1961450

 

[aelfwyne]

Well, that's the whole point..... Auto was setting a couple of the values WAY more agressive than even the memory's own SPD recommended. Apparently this motherboard doesn't use the SPD values for everything, which was making the memory less stable when using auto. I used RightMark Memory Analyzer to find the full SPD values (most programs only show some of these not all), and entered the values specified by the SPD in manually, and it was more stable.

 

[SparkyJJO]

In my case my mobo was setting the memory looser than it should be. It stuck it at 3-3-3-7 when it is supposed to be 2.5-3-3-6. All of it is on manual now, also because when overclocking my system I needed to loosen some minor timings.

 

[n7]

Auto or SPD settings have never been something i'd recommend using.

If you are building your own PC, i do not believe it's that hard to learn what TCL - TRCD -TRP - TRAS do, or how to set them.

Or, if you are too lazy to learn what those settings do, then at least be smart enough to realize things may not run as they should.

SPD is merely designed to get you into the bios off the first boot IMO.
Then you can change vdimm & timings accordingly.

 

[Malk]

I experienced the same thing on my P5B Deluxe, it booted fine with RAM clocked to 840 Mhz, but when i set it to "Auto" it set the divider so the RAM only ran 640 MHz, and it would not boot.

 

[tempoct]

Originally posted by: Malk
I experienced the same thing on my P5B Deluxe, it booted fine with RAM clocked to 840 Mhz, but when i set it to "Auto" it set the divider so the RAM only ran 640 MHz, and it would not boot.

uh, I should be clear. Auto I set if for timing only, the DDR speed is best set manual.