AMD's SB750: Enabling Higher Phenom Overclocks?
by Gary Key on July 23, 2008 12:00 AM EST- Posted in
- CPUs
Testing the Theory - Does it Overclock Any Better?
We started by getting a reference overclock out of one of our Phenom processors, in this case a Phenom X4 9850BE. We picked this processor as it has difficulties clocking past 3.1GHz. In fact, this processor seemed to hit a wall around 3.0GHz and changing the HT Ref Clock past 200 just made matters worse as attainable clock speeds would actually decrease. Even then, we had to tune just about every setting in the BIOS to have a stable platform in the 3.0GHz range. Our initial results with this CPU matched the profile that AMD told us would probably benefit the most from ACC.
We will also provide results with our newly arrived Phenom X4 9950BE that seems to be the pick of the retail lot in early testing. For those of you with the earlier B2 stepping 9600BE, we hope to have results shortly. While ACC should provide benefits such as higher clocks or lower voltages, we were skeptical as to any benefits we would gain with a processor that does not seem to need any tuning. As it turned out, our intuition was almost on the money. We ended up with a 100MHz higher core speed but that was about it. Although not shown, the biggest improvement with ACC came in the 2.6GHz to 3.0GHz range where we could set NB speed to 2.6GHz with absolute stability. With ACC switched off, our NB speed dropped to 2.4GHz and processor voltage at 3.0GHz increased to 1.35V compared to the stock 1.304V.
| Phenom 9850BE - Highest Core Speed / Stock Voltages | ||||||
| Vista 32 | Core Speed | HT Ref Clock | HT Link Speed | North Bridge Speed | Memory Speed | CPU VID |
| Foxconn A79A-S ACC On | 3000 | 200 | 2000 | 2000 | 1066 | 1.312V |
| Foxconn A79A-S ACC Off | 2800 | 200 | 2000 | 2000 | 1066 | 1.312V |
| ASUS M3A32-MVP No ACC | 2800 | 200 | 2000 | 2200 | 1066 | 1.312V |
| . | ||||||
At stock voltages and stock HT/NB speeds, the highest our 9850BE sample would reach was 2.80GHz. This was true on both the ASUS M3A32-MVP as well as the Foxconn A79A-S. Turning on ACC let us hit 3.0GHz without adjusting the CPU's voltage at all. So far, so good.
| Phenom 9850BE - Highest Core Speed / HT Ref Clock | ||||||
| Vista 32 | Core Speed | HT Ref Clock | HT Link Speed | North Bridge Speed | Memory Speed | CPU VID |
| Foxconn A79A-S ACC Off | 3280 | 205 | 2050 | 2255 | 1093 | 1.4250V |
| Foxconn A79A-S ACC Off | 2870 | 205 | 2050 | 2255 | 1093 | 1.4125V |
| ASUS M3A32-MVP No ACC | 2970 | 205 | 2050 | 2255 | 1093 | 1.4000V |
| . | ||||||
This particular CPU acts really strange when trying to increase the HT frequency, anything over 205MHz usually meant decreasing clocks in a hurry, no matter voltages, NB speeds, or HT settings. We found it amazing that turning on ACC all of a sudden allowed a 410MHz increase on the Foxconn board and 310 compared to the SB600 board..all with a minimal increase in CPU voltage.
The CPU would not even post past 2970 on the Foxconn board, regardless of using the BIOS or AOD for clocking, we had to drop to 2870 for stability. On the ASUS board it was fine at 2970 but going over 3GHz meant locks or non-POST situation. There is a wall with this particular CPU and ACC does something for it... that was the one test that just amazed us.. the rest are semi-interesting.
| Phenom 9850BE - Highest Core Speed | ||||||
| Vista 32 | Core Speed | HT Ref Clock | HT Link Speed | North Bridge Speed | Memory Speed | CPU VID |
| Foxconn A79A-S ACC On | 3400 | 200 | 2000 | 2200 | 1066 | 1.4750V |
| Foxconn A79A-S ACC Off | 3100 | 200 | 2000 | 2200 | 1066 | 1.4375V |
| ASUS M3A32-MVP No ACC | 3100 | 200 | 2000 | 2200 | 1066 | 1.4250V |
| . | ||||||
If we simply push for highest core speed, ACC makes a 300MHz difference. Our 9850 could hit 3.1GHz on the two reference configurations, but 3.4GHz was possible on the A79A-S with ACC enabled.
Next we tried a retail Phenom 9950 BE:
| Phenom 9950BE - Highest Core Speed | ||||||
| Vista 32 | Core Speed | HT Ref Clock | HT Link Speed | North Bridge Speed | Memory Speed | CPU VID |
| Foxconn A79A-S ACC On | 3500 | 200 | 2000 | 2400 | 1066 | 1.4750V |
| Foxconn A79A-S ACC Off | 3400 | 200 | 2000 | 2400 | 1066 | 1.4750V |
| ASUS M3A32-MVP No ACC | 3400 | 200 | 2000 | 2200 | 1066 | 1.4675V |
| . | ||||||
Our latest retail Phenom X4 9950 Black Edition overclocks quite well, 3.4GHz isn't a problem. Here ACC doesn't make much of a difference at all, 100MHz is all we get.
We have included performance result screen shots in the following gallery.
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wingless - Wednesday, July 23, 2008 - link
"In the end, we know after a good 60 hours of testing, over 600 different settings, 400+ screen shots, and countless reboots that Advanced Clock Calibration works, yet we do not know anymore about ACC at this point from AMD than SpongeBob SquarePants."AMD does nothing but right their wrongs these days. The SB750 is gonna be big for them. I'm amazed that Anandtech went through so many combinations trying to bring this thing down. They have proven without a doubt that this technology works.
I also can't wait until next week. They have given us confirmation that 790GX and 790FX boards with SB750 will be coming out NEXT WEEK! Also they keep mentioning some part that they "dare not mention". WTF is that going to be? I thought 790GX+SB750 was going to be the big news. Theres something else? Next week will be exciting for AMD in all the GOOD ways.
ZootyGray - Thursday, July 24, 2008 - link
Yup - I come here to hear about the results of what I call "brutal testing" rather than read somebody's hype or bias or sloppy inconclusive testing. I am still fairly new here but I believe Anandtech is the real thing.I want that to be true, esp. after wasting my time at tom's bubblegum guide with there trash bias garbage misleading bullschtein socalled reviews.
These guys are working hard to get the real goods - and in contact with AMD, delaying reports promised 'tomorrow' - who cares - they are willing to go to amazing lengths to output accurate info after deeper investigation.
This is no kiddy's website - it's a hard read to get through it; and I know I am not the only one who will reread it to better comprehend what I missed the first time through. This testing is consistent with the articles on 'the 3 amigos' and the one about the recent additions to the AMD line, including the 9950. Take it apart, what makes it squeal.
Also, it seems there is something different about the 9950, and it's not just an oclok 9850.
Looking forward to more next week - and the ?? mystery ?? item????
Big change on the AMD scene - wow.
Calin - Thursday, July 24, 2008 - link
I've quit reading Tom's Hardware long time ago - when I think it was a good site. However, Anandtech was better overall, and one site was enough :)As for in depth reviews... this should qualify as an easy reading, look for the technology behind NVidia's 280 and 260 series GPU for a "transistor-oriented" article - that's a hard read indeed
Comdrpopnfresh - Wednesday, July 23, 2008 - link
I am really interested to see how an ASUS or DFI board with the new sb do in overclocking and performance. As mentioned this board is more of a feature-rich pick. And just looking at the charts of ACC off on the foxconn vs the ASUS with sb600, I hope there will be more of an improvement with a fresh sb750 variant.Interesting though about the pci-e 1.1 and lan choices by amd. Is it possible having those two remedied would hinder the improvement by ACC?
Really looking forward to new comparisons to Intel chips with the new change. Hopefully with 45nm parts and ACC, amd can have a good go.
One thing I would like to know though: What are the specs on the sb750 foxconn vs the asus sb600 in terms of the number of phases in power delivery?
Goty - Wednesday, July 23, 2008 - link
I think that there must be some underlying issue with either the chipset drivers or windows itself when it comes to differing final overclocks, as the CPU shouldn't necessarily be aware of what kind of software its running, other than the fact that a few more registers are being used. IS there any evidence that this is a Phenom-specific issue, or might it affect Athlon64's as well?Locutus465 - Thursday, July 24, 2008 - link
Quite honestly, either way I would run 64bit over 32bit any day of the week period... I'm sorry but the little bit of extra performance you get OCing really doesn't out weigh the many many advantages 64b vista has over the 32b variant (and over XP). Simply put, 32bit operating systems are all but done in my home... I do run 32bit vista on my laptop but only for the following reasons:HP put 32bit on here, and it seems to me all their custom drivers and software (which seem to be required to keep the system from crashing) are all 32bit... so oh well.
This is a budget laptop to begin with and it maxes out at 2GB RAM... The extra overhead of 64b would just be more of a performance killer than anything else.
No gaming will be done on this laptop (so no need to worry about future games needing more that 2GB for a process) and I have my desktop at home if I need to manipulate large flat files.
Now my desktop? Yeah...
Phenom 9850BE
4GB OCz DDR2
Radeon 3870...
It's getting the 64bit treatment all the way :)
CyberHawk - Wednesday, July 23, 2008 - link
... boy, I was waiting for this one :DFireTech - Wednesday, July 23, 2008 - link
So was I ;)It leaves me with more questions than answers though. Time to re-read and await further developements/articles.