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GNR

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Today I got the Phenom 2 940 and said I should try it first on my M2A-VM mobo instead of buying a 790GX mobo just for a new upgrade "am2" cpu.

Phenom2 works fine on this board although it is not officially supported and it showed as "unknown processor" in the bios.

In the beginning I saw some awful benchmarks compared to various reviews I found online. Thankfully I fixed those. There were 2 reasons the performance was pretty bad compared to the reviews:

First the mighty Cool n' Quiet. With that enabled, single threaded benchmarks were around 40% slower than the reviews. I know that Phenom1 had that bug and Phenom2 has fixed it, but it apparently needs official support with BIOS or something. Anyway CnQ = Disabled.

The second reason was more sneaky. In Wprime and various Sandra tests I had around 20% lower scores. I though that was my slow memory (I have 4x2GB 800mhz kingston value with 5-5-5-18) but it wasn't. A new option appeared in the bios with this CPU (X2 6000+ didn't had it) named "Unganged Mode". It was in unganged mode by default and once I switched to Ganged all the scores were almost the same with the reviews. For a strange reason I had better results than the reviews on memory bandwidth benchs even though I have pretty low end ram modules.

Anyway in some benchmarks slightly lower and in some slightly higher than the high end hardware reviews. Pretty good results if you ask me.

Now with overclocking, I wasn't expecting much from this board. I managed to boot into Vista x64 with 3.6Ghz and 1.5v, but once I started a benchmark I BSODed after a while. Apparently my motherboard couldn't keep the voltage stable at 1.5v. Before BSODing I could see the voltage drop to 1.4. Finally I settled with 3.2ghz and 0.05 CPU Volt increase just for safety. I tested the power consumption and it seems the same with the X2 6000+ @ 3.3ghz that I had before upgrading. I was running that for a year so I feel pretty safe with the 3.2Ghz on the P2 for everyday use.


So for anyone that has some old AM2 motherboard that at least supports X2 6000+ 125w, and hopefully has that "ganged mode" option, phenom 2 is a great upgrade. I wouldn't recommend the black 940 for use on those motherboards though as you can't get so great overclocks. I think a p2 920 will easily reach 3.2ghz without multiplier and from my experience this was the max stable oc on my budget board.
 

medjohnson77

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That is interesting, when I first got my 9850be I tried putting it in my Asus M2N32 sli wi/fi deluxe 590 chipset, before they had the bios update for the 9850be and I ran into all kinds of problems. I posted on here about it, had a lot of people dogging me about dropping it in before the bios came out to support it. Other people I talke to dropped it in before bios updates and some got a 3.1ghz over clock stable.

I have since upgraded to the 940 dragon and also upgraded my mother board up from a Jetway HA04 extreme 600sb to a Asus m-79T with the 750sb. Much better overclocks with 750sb chipset. So I might just take my 6400+be out of the M2N32 and drop the 9850be in again and see what happens. I have updated the bios way back so it should run, maybe I will drop the new 940 dragon in there and see how it benchs...
 

sandeepb

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I've managed to get the Phenom 940 up to 3.8Ghz with a voltage of 1.45v. I think I'm quite happy with that and will be keeping it. I have been running a whole day with this set and there's no stability issues.

Finally a phenom I bought that overclocks! :) (my previous 9850BE couldn't hold 2.6Ghz)
 

medjohnson77

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Sandeepb,

How long did you wait before you started overclocking it if at all?? I have not overclocked mine yet, still running at stock. Not sure if it matters or not, but we will see what she can do in a few days maybe. Nice over clock btw, I hope mine will hit that a those volts, did you change any other settings?? NB volts other things? What are your temps, and what kinda of cooling are you running?
 

jimmysmitty

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Yea but she is a low power girl. I think they will have to release a sub 65w TDP quad for her to get one.
 

GNR

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Ok guys finally I settled with 3.3ghz on the Phenom 2 with a +100mv. 5 hours prime stable, so everything seems good to me. It is funny that this Phenom2 behaves exactly like my previous X2 6000+ that I also had oced at 3.3ghz with +100mv. And it also seems to have exactly the same power consumption. Phenom2 temperatures are lower though.

Anyway here are some screenshots from CPUz and some benchmarks so you can compare the performance of AM2 vs AM2+ motherboards.











 

sleekgtz

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Hey GNR, thanks for the great info! Getting the Phenon would save me money instead of upgrading the whole machine.

I also have the M2A-VM motherboard, I was wondering if your mobo has the HDMI option. I'm planning to get the P2 920 like you said, instead of the 940. My ram is currently 2gb but I'll update that soon to 4gb. Right now I'm running XP Pro, is it worth it to upgrade to Vista 32/64?

Thanks!
 

GNR

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sleekgtz, yes you should get the 920 it is a very good upgrade. Basically you will have a high end system with a cheap mobo. I don't understand why Asus hasn't officially supported Phenom2 on this board because the power requirements are lower than the 6000+ and 6400+ that work great on this board.

Anyway just a reminder once you get it:

Disable Cool n Quiet
Enable Ganged mode on RAM
And have the latest bios (2201)
 

sleekgtz

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What a bummer, my M2A-VM motherboard is toast!!!

I already got the latest bios 2201 installed. Then I tried to update it again with the same 2201 version but with a different boot image using MyLogo2, that worked. But then I tried to change my image again using the same process and my machine just hangs on the boot image, nothing happens! I tried various things and also did the hard reset for my CMOS but that didn't work.

Oh well, lessons learned. I just ordered a new motherboard from newegg that will support AM2+. :D

 

pmc650r

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I too noticed slow-down with Cool N Quiet enabled on my new Phenom II (720). With CNQ enabled, single process client VM performance is WORSE (much worse) than with the Athlon 5200 (also with CNQ enabled) it replaced. CPU-Z shows that the CNQ driver isn't smart enough to trigger the next higher performance state, even when it's really needed. With CNQ disabled, performance is great, but, the system uses 23 more watts while idling (106 vs 83).

According to multiple web sites, this appears to be a problem specific to XP. Vista has a built-in performance state driver that reportedly works better, I haven't seen it for myself though.

I found a few people with the same problem, but no good solution, so, I decided to write my own CNQ driver (actually, it's a service). I've been very happy with the performance so far. Maybe it will work for you too. The source and executable may be found here: http://home.comcast.net/~pmc650/site/?/page/CNQ_Phenom_II_WinXP32/
 

Potato_Peeler

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GNR: Thank-you! On the strength of your post/thread, I got a Phenom II 920.

Questions:

Unganged vs. Ganged. You said that you saw an entry for Ganged vs. Unganged in the BIOS and were able to change it to Ganged. I don't see such an entry. I should say that I've got a 2 x 2GB Kingston DDR-800 and 2 x 2GB Kingston DDR-667, so I'm not sure if mixing 2 types of DDR affects "ganging" or not. Also, I'm using the onboard video. Also not sure if this prevents the option of ganging showing up as an option or not.

BIOS and CPU recognition: I'm using the lastest on the Asus site for the M2A-VM: 2302, dated Feb 16, 2009. But during the POST, I still get: AMD Processor Unknown. Digging into the BIOS (which as all settings on Auto), I see that it has figured out that it's a 2800MHz chip. I was hoping this latest BIOS would support it (or at least recognize the PH2).

Not 100% bootup. Not sure if it's power supply related but when I first powered it on, the PC didn't boot. The fans came on but just a black screen, no POST, no beep. I thought, darn it's not compatible. But a subsequent power down/up and it booted ok. I was able to Memtest it for a few minutes with no problem. Does your PC reliably boot every time? My concern here is that it's a server and upon the return of power from an outage, I'd like it to always boot up.

 

Potato_Peeler

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I snooped around on the Internet for Ganged vs. Unganged information.

It seems that:

1) it doesn't matter much for everyday use
2) for multithreaded usage, use UNganged
3) for max single threaded performance, use Ganged
4) difference is like about 1% or less.

I am thus no longer worried about Ganged vs. Unganged and am leaving it UNganged because I'm using my 920-pumped up ghetto box for virtualization, which is sort of multithreaded.

Reference links I found useful:

http://ixbtlabs.com/articles3/cpu/amd-phenom-x4-9850-ganged-unganged-p1.html
http://www.overclock.net/amd-memory/324052-ganged-vs-unganged-mode-5.html
http://www.xtremesystems.org/forums/showthread.php?t=166222


 

GNR

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Potato I know that there is not great difference in unganged/ganged, but in that specific motherboard (M2A-VM) with the Phenom2 the performance difference with all benchmarks was huge because of some bug probably. I suggest you set it to Ganged. That and the Cool N quite to OFF, as this is bugged as well.

I no longer have that board with my Phenom 2 because I needed to build a second AMD system and I bought an Asrock 790GX, but for the 1 month that I used it that way I had absolutely no problems.

You can test easily if unganged is bugged in your motherboard. With the Phenom 920 the fast WPrime ( http://www.wprime.net/ ) score should be around 12-13 seconds. If you have something else your CPU is not working good.
 

garydale

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Thanks man. I saw a link to your post on the ASUS forums for the M2A-VM board. They've confirmed your report with other Phenom II processors. Apparently you do need the latest BIOS (2302) and may have to reset your CMOS, but apart from "unknown processor" report, it looks like the Phenom IIs work well.

I've been putting off upgrading from my old processor because I thought I'd need a new MB too. However it looks like the biggest headache is choosing which Phenom II to drop in. :)
 

light401

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Yea amdfangirl.

I have a M2A-VM here too, and i'm running my Phenom II X3 720 BE and it's working really great. No problems found. Just updated the bios to the latest, which right now is 2302 and threw the processor in.

I'm now running some tests to compare the phenom's performance in M2A-VM and then i will do the same in my M4A78 PLUS which is on its way. That will solve my questions about the HT limitting the phenom II performance. Some people say it does, some say it doesnt. For me, it does, otherwise amd wouldn't have any reason to increase it as they launch new sockets. And I also read in some review site that the faster the HT, the faster it will relate with the L3 cache and etc, so the HT of my M2A-VM must be bottlenecking it right now. I shall know the truth this monday or tuesday ;)
 

ralpha1961

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I installed the latest Athlon II x4 620 Propus 2.6Ghz on the M2A-VM and it works! Best bang for the buck on a two year old board. Good work AMD.
 
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