Thanks TONY - drive strength helps coldbug

[mike]

Here is what Tony wrote in the RDX thread:

Cold bug

As you chill a cpu the drive strength from the memory controller increases, so you start overdriving the memory.

So, you have to weaken the drive, you can ONLY do this on the motherboard. You have to switch in resistors that alter the drive weaker or stronger depending on the resistance used. This is also one of the ways you tune a motherboard to clock ram well or a specific type of ram..IE...TCCD etc.

Now its not a full on cure to the cpu overdriving the ram, but if tweaked correctly it will allow a higher fsb to be reached.

So...Cold bug is not a serious issue, its just because the cpu's are not designed to run -50 from the onset, but to say nothing can be done on the motherboard is not true....the only way to even half fix the issue is with tweaks on the motherboard or design the cpu to run at -50 or lower.

Testing at ATI of Gruper and halibut proved this theory correct, if it didn't work we would not have designed it into the board. It won't work for everyone as every cpu is different, but it will help.

Any further explanation should have to come from Tony - as far as my knowledge to this goes would be totally insufficient.

All I can share is one of my many experiences of struggling with the coldbug that gives a secnario of where Tony's advise worked

I received from our XXX-IP Steven a X2 4600+ that had no coldbug - no coldbug insofar that it would not crash at a certain temperatures as most AMD will. I could pull the core temperatures down to -100C ( the container bottom temps ~ -160C) and it wouldn't crash.

But my OCs would be almost on the same level as running on cold water.

Trying lots of various things in fighting to get the clocks up I often would set all the ram settings to default - which would often even worsen things I decided to go back to Step 1 and slowly work my way down in temperatures.

I don't really remember the real settings but from my memory it was like that:

1) Air (~ 40C core)
with Drive Data strengths 7/4 - CPU clocks ~2.8GHZ

2) Single Stage Phasechange ( ~ -15C core )
with Drive Data strengths 7/4 CPU clocks ~2.8GHZ
with Drive Data strengths 7/2 CPU clocks ~3.1GHZ

3) Dry Ice (~ -40C core)
with Drive Data strengths 7/4 CPU clocks nothing - lol
with Drive Data strengths 7/3 CPU clocks ~2.8GHZ
with Drive Data strengths 5/2 CPU clocks ~3.3GHZ

4) LN2
with Drive Data strengths 7/4 - CPU clocks ~2.8GHZ

haven't gotten around to run it yet again - but hopefully I'll get to 3.6GHZ on the dual core X2 this time around with better settings
Again I don't reall remember the right settings clocks - but this should help to get an idea...



In the past I had rigged the perfect ram and system settings on air - so that under cold I could only focus on finding the propper vcores and mhz.
Turns out that the ram timings - in particular the drive and data settings can vary greatly under different temps. The settings might only need a slight shift - again in particular the data and drive strength - that can turn a perfect rig into no boot and vice versa. The window is VERY SMALL of good and bad ( crash). The colder it gets then narrower the range gets.
This small range of good and bad - often made me stop early in the quest of combatting the Cbug - espcially when running tube ( dry ice / ln2) your exploration of the ram sttings seems too tedious of a task and I have that feeling more than a few people have run into similar problems like that.

Recently, by pure laziness - or axiousness to find out what the max is before I even know the cpu - I had been prepping my rigs under cold for the first boot and realized that my OCs started to get better and better than other peeps - especially with weeks of CPUs that weren't supposed to be doing too well under cold...

All this and many other experiences helped me to see the value in what Tony had said above. Hopefully Tony can elaborate some more on his findings.