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Unique Sandy Bridge Question - Curious

post #1 of 6
Thread Starter 
As many of you know, I had a lemon of a motherboard (or processor), and I never got to pinpoint which it was. I got to return both for a 100% refund. But out of pure curiosity, I'm trying to figure out what it was which was causing my issue. The system never crashed, and it seemed like whatever my problem was, was a built-in feature which shouldn't have been there in the first place (yet it was).

On the Sandy Bridge 2600k, the bus speed is supposed to remain at a constant 100MHz. The multiplier is then altered to get your desired overclock. With my old Asus Pro 1155 board, no matter what was done, if an overclock was attempted without the turbo boost on, the max clock speed was 3.4GHz (no matter what multiplier I set it would stop at 34x once booted up, while in the bios it'd show a multi of 42x if I wanted 4.2GHz). If I turned turboboost on, and I attempted an overclock through the base clock or the turbo clock, the multiplier would go to the desired amount, and the bus speed would intelligently downclock itself to ensure my max clock speed remained at 3.4GHz even if the multiplier was 42x. If I set everything to stock, the turbo boost would kick in, and in fact my multiplier would hit 38x as turbo boost was supposed to go to, but my bus would downclock subsequently. The highest my bus speed would ever reach was 95MHz, and lowest it went was about 60MHz. Sometimes it would spike to 200MHz and the multiplier went down to 16x (who knows why). I can assure you that I know exactly what I was doing with my motherboard settings, and I tried various options (with the stock BIOS and the updated BIOS). I tried clearing the cmos, switching RAM, and taking the motherboard battery out. I tried manually setting my bus speed via BIOS, and that did nothing. Believe me, something was wrong.

But the weird thing to me (the reason I'm curious) is that this seemed like a built in feature. Think about it: The max clock speed kept itself at 3.4GHz no matter what, and would intelligently downclock my bus speed to ensure this would happen. My computer functioned properly and never crashed either. I could run Prime95 in any way, I could run SC2, I could run all the different benchmarks, and I had no problems whatsoever. But the bus speed was fluctuating.

I have done research and can't find a single person who had this issue with my older motherboard which I returned. I had the bus speed set to 100MHz (I also tried "auto"), and under both settings the bus speed would fluctuate when everything was booted up.

So I wonder what was the problem, and why something so odd happened. Normally one would expect such a problem to cause crashes and warrant a definite need for replacement. But in this situation, everything worked... it's just turbo boost wasn't working properly, overclocking didn't work, and the bus speed wouldn't hold still. Again, I'm only curious because:
A) The system was stable, and;
B) The system seemed to intelligently clock the bus speed to maintain a consistent core clock, which is nothing anyone has ever heard of on the 1155 socket
Edited by PaulWog - 1/20/11 at 5:28pm
    
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post #2 of 6
Strange, mine flactuates to 99.8
post #3 of 6
the base clock was never at 200 nor 60, that is CPU-Z as the problem no reporting correctly, it seems like ONLY on ASUS boards does the bus speed fluctuate. Probably a BIOS thing, and teh turbo thing is there so it kinda sucks.
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post #4 of 6
Thread Starter 
Quote:
Originally Posted by Sin0822 View Post
the base clock was never at 200 nor 60, that is CPU-Z as the problem no reporting correctly, it seems like ONLY on ASUS boards does the bus speed fluctuate. Probably a BIOS thing, and teh turbo thing is there so it kinda sucks.
Hmmm still though, why would it be reporting the correct multiplier and the incorrect bus speed? I had the multplier set to 54x once, and I was stable... meaning if the bus speed really was 100MHz, then I was running 5.4GHz at 1.3v, which I highly doubt was the case (since I was stressing it with prime95).

You sure the bus speed couldn't have been fluctuating? I mean something obviously wouldn't let me hit the multipliers I set (I tried all different settings).
    
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post #5 of 6
yea you can't do 5.4ghz on 1.3v LOL

yes that board is very weird. No the bus cannot be 200mhz, because everything else on the bus would be at 200mhz and that won't ever happen. Try it yourself try setting 107blck see if you can even do that. To high or too low the buss speed is tied to so many things in the processor, the ringbus that basically runs off the 100mhz bus cannot do 200mhz or 60mhz
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post #6 of 6
Thread Starter 
Quote:
Originally Posted by Sin0822 View Post
yea you can't do 5.4ghz on 1.3v LOL

yes that board is very weird. No the bus cannot be 200mhz, because everything else on the bus would be at 200mhz and that won't ever happen. Try it yourself try setting 107blck see if you can even do that. To high or too low the buss speed is tied to so many things in the processor, the ringbus that basically runs off the 100mhz bus cannot do 200mhz or 60mhz
I know 5.4GHz at 1.3v cannot be done. I was simply expressing a point about what was going on, and that if I attempted to do so, it would run stable (meaning it wasn't hitting 5.4GHz).

Well, I think I'll stop looking into the problem now. I am picking up my new processor today, I already have my new motherboard (sig), so I should be good-to-go. I'm looking forward to seeing if someone else one day has this same problem and comes here asking.
    
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