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How do i unlock 4th core on Phenom II x3 720?

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March 16, 2009 5:37:03 AM

I heard it has to do with the motherboard's BIOs, so, here's mine:


GIGABYTE GA-MA790FXT-UD5P AM3 DDR3 AMD 790FX ATX AMD Motherboard - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

How exactly do you do so?

More about : unlock 4th core phenom 720

a b À AMD
a c 99 V Motherboard
a b K Overclocking
March 16, 2009 5:52:00 AM

I'm not sure you can. It takes a special bios, and I believe a board from Biostar. Not all boards will allow this.
March 16, 2009 5:54:04 AM

ahhh, that's ok... just wondering if i could.

is there some sort of list of boards said to support the unlocking of 4th core?
Related resources
March 16, 2009 6:21:26 AM

it would also depends on if that 4th core is really defective (hence it will never work), or if it was working, and just disabled to turn it into an X3.
a b V Motherboard
a b K Overclocking
March 16, 2009 11:45:24 AM

If you would have bought a Phenom II 920, I am pretty sure all 4 cores on them work perfectly staight out of the box.
a b À AMD
a c 99 V Motherboard
a b K Overclocking
March 16, 2009 1:08:30 PM

Yeah, but where is the fun in that?

March 16, 2009 2:07:49 PM

I can't guarantee anything, however:

From what I remember reading, most Gigabyte and Biostar 790 chipset boards worked in unlocking the 4th core using the ACC feature by setting it to Auto.

But if your disabled core is really defective, it won't do you any good.

As I also understood it, Asus boards would not unlock because their chipset/BIOS stuff was customized.

That's what I remember reading about. I can't verify any board except for the Biostar TA790GX 128M mobo I bought and it worked.

However, your results may vary and I can't guarantee anything.
March 16, 2009 10:03:44 PM

hmm, dunno if it's worth it, would my computer boot IF the 4th core was indeed defective? like, as in, the other 3 cores still run with the half-a$$ed core?
March 17, 2009 1:34:56 AM

You need a 790GX chipset and apparently the BioStars are the best for unlocking.

If your computer didn't boot you would just have to clear the CMOS and restore default BIOS.
March 18, 2009 1:10:41 AM

I think it's more dependent on your CPU. Some people are suggesting that fully functional 4-core phenom IIs were intentionally disabled to meet launch and could explained why initial responses were very positive. I don't know if that's true or not but it would be great if we could collect a comprehensive data base of build dates to find "stable" 4th core batches. :D 

I was one of the lucky ones to get a stable 4-core 720x3. I had all four cores up to 3.4 stable at one point with voltage adjustment but found the increase noise of my CPU fan a little too loud for my taste. :p  Less Noise > Marginal CPU gain.

BTW, I'm using a Asrock 790GX motherboard and it works great.
March 30, 2009 6:25:12 PM

jitpublisher said:
If you would have bought a Phenom II 920, I am pretty sure all 4 cores on them work perfectly staight out of the box.



Is the x4 920 a BE? Or AM3?
March 30, 2009 10:09:38 PM

X4 920 is not BE, and it's AM2+.

The AM3 versions should come out this April, i believe.
April 17, 2009 10:58:15 AM

It is AM3 but it also suit to AM2 :) 
April 18, 2009 11:11:37 PM

I've got a Biostar TA790GX Motherboard and a Phenom 2 X3 720 BE CPU. I had no asperations of trying to get a fourth core from the three core processor but after reading the article on Tom's Hardware concerning their attempts at unlocking the fourth core with limited success I decided to enable the ACC in my bios and instantly after rebooting I came up with what appears to be a stable fourth core. I ran Cinebench for establishing a bench mark between the two cores (three and four) and here are the results:

Three Cores:
Rendering (Single CPU): 3226 CB-CPU
Rendering (Multiple CPU): 8582 CB-CPU

Four Cores:
Rendering (Single CPU): 3177 CB-CPU
Rendering (Multiple CPU): 11533 CB-CPU

The change appears to be completely stable at this point but could someone suggest some other benchmark tests that would push the limits of the current four cores to check on it's future stability? I've never been one in the past to run benchmark tests on my new builds. Based on the article I'm not sure if the change from the three to four core processor provides me any added benefits but I'm tempted to leave as four if there isn't any stability problems. What do you think?


April 19, 2009 9:50:14 PM

run prime95
April 19, 2009 11:18:46 PM

Quote:
run prime95


Thanks jjbtexas for the suggestion. I came across Prime95 (Win 64 bit) this morning and ran it for about 9 hours with the new unlocked CPU passing every test so I guess that puts a dent in the comments I read about the X3's being built from defective X4's.
April 20, 2009 8:31:01 AM

but, why would AMD deliberately disable good functioning cores and sell it as a cheaper 3-core? Don't they make more money in the first place by selling a AM3 Phenom II quad?
April 20, 2009 11:06:19 AM

they don't, all of them are slightly defective, except one batch which was to meet demand.

and don't forget the 720 is in a fairly high demand due to being better and cheaper than the e8400.
April 20, 2009 11:26:47 AM

so, there's this particular batch of good quads that went on to sell as triples? Dunno if mine's one of them...
April 20, 2009 11:28:19 AM

it was in late february/early march so I doubt you have one
April 20, 2009 11:33:35 AM

lemme see my order date... i ordered mine on March 4th... That counts as early march... but then again it's luck of the draw.
May 13, 2009 11:21:23 PM

MykC said:
You need a 790GX chipset and apparently the BioStars are the best for unlocking.

If your computer didn't boot you would just have to clear the CMOS and restore default BIOS.


how exactly do you clear the CMOS and restore default BIOS?
May 14, 2009 12:28:15 AM

successful_troll said:
Cheater...

:heink:  ???
Cheating at what? was there a point to your post? It does not make any sense!

anybody respond on how to restore CMOS and BIOS in case it was unsuccessful?
May 14, 2009 10:12:14 AM

on some mobo's there is a cmos restore switch.
May 29, 2009 7:36:38 AM

are the 720s the only ones that can be unlocked? I have a 710...
May 29, 2009 8:10:56 AM

kal20mx said:
are the 720s the only ones that can be unlocked? I have a 710...

both of them can be unlocked, they're both quads with one core disabled anyway... only difference is that the 710 is basically a locked, lower speed version of the 720.
June 3, 2009 8:59:46 AM

go into bios press Ctrl + F1 go into overclocking tweak at top you will see ACC( advance clock calibration set to hybrid and all cores.you will have 4 cores on reboot...
June 3, 2009 1:03:10 PM

Same game as the ol celeron proc. Defective math-co. No prob we will lock it out and sell it in a Dell... lol
June 3, 2009 6:13:06 PM

extremebadass said:
go into bios press Ctrl + F1 go into overclocking tweak at top you will see ACC( advance clock calibration set to hybrid and all cores.you will have 4 cores on reboot...
]http://valid.canardpc.com/cache/banner/578355.png


I thought you set them to "auto"? Are u sure you have the same mobo as me? (GIGABYTE GA-MA790FXT-UD5P)

oh wait, you have the UD4P one, but they both should be similar, i guess... anyway...

What clock speed and voltage was the tri-core at before you enabled the ACC option? I want something to start off from, since i have it at 3.2 Ghz at stock voltage, do i have to up the voltage to unlock it?
June 6, 2009 10:29:17 PM

I'm ordering a 720 right now for my first computer build.

Would you recommend trying this? Does it void the warranty? Does is reduce the CPU's lifespan?

I'm very leery of overclocking, and even more leery of enabling a "defective core."

I don't want to fry my first CPU within a year or two, because I do not have the money to buy another.
June 6, 2009 11:22:09 PM

trust me, the 720 is very cool, especially when overclocked, even on the stock cooler.

mine's at 3.4 Ghz, with a 1.350 voltage, which is only a tick above normal. I'll say 3.4 Ghz is where it is at, you can go higher, but i'll recommend a better cooler. For stock, it's 30C at idle and 45C load (playing FSX, the most CPU intensive game i have)

but still, i'm on the fence about unlocking it, even though i bought it when it first came out (higher chance of success), but still... you never know, and taking apart the case and hitting the CMOS switch is a PAIN IN THE ASS if that's the worst-case scenario.
June 8, 2009 7:16:16 AM

alright, thanks for the info on unlocking, but i'm still scared about doing it...

Any successful unlocker, what was your Ghz speed and voltage before you unlocked it?

right now i have it at 3.4 Ghz on 1.35 volt... should i clock back to 2.8 and leave the voltage the same?
June 8, 2009 8:52:29 AM

Couldnt unlock my 4th core :( .. oh well i wasnt expecting it to when i bought the tricore. Still have my 710 clocked at 3.5 with 1.35 for a while but have it at 3.2 just to be safe.
June 8, 2009 7:23:33 PM

extremebadass said:
go into bios press Ctrl + F1 go into overclocking tweak at top you will see ACC( advance clock calibration set to hybrid and all cores.you will have 4 cores on reboot...
]http://valid.canardpc.com/cache/banner/578355.png

Hey extreme! I have the Gigabyte MA790GP-UD4H mobo with the F3A bios. I set to ACC hybrid and all cores and i couldnt reboot. Also tried per core and normal/auto, still no luck. Got my cpu in may so i am probly just one of the unlucky ones unless you have any suggestions for me. Thank you.
June 30, 2009 10:35:49 AM

I've used All cores and Auto.It actually works better on Auto more stable at high oc.On ALL CORES you can adjust the % of oc on each individual core. Wind down the 4th core if unstable..As for the bro with the 720 that crashes on boot with 4th core activated try cranking your vcore voltage up to 1.45 -1.5 and wind down your ram e.g if its 1600hz knock it back to 1333 if its 1333 knock it down to 1066 and make sure your ram voltage is set to ram specs not board specs.Same with your ram timings.At the moment ive got my ram set at 1.8 volts. 1333 hz 7,7,7,24.Corsair XMS3 1600 hz. Works best for gaming....Change your bios to F4 or f4g .Some bios don't work i've been told.I have tried these 2 and they work. :hello:  :sol:  :sol:  :sol:  :sol: 
July 3, 2009 3:38:56 AM

extremebadass said:
I've used All cores and Auto.It actually works better on Auto more stable at high oc.On ALL CORES you can adjust the % of oc on each individual core. Wind down the 4th core if unstable..As for the bro with the 720 that crashes on boot with 4th core activated try cranking your vcore voltage up to 1.45 -1.5 and wind down your ram e.g if its 1600hz knock it back to 1333 if its 1333 knock it down to 1066 and make sure your ram voltage is set to ram specs not board specs.Same with your ram timings.At the moment ive got my ram set at 1.8 volts. 1333 hz 7,7,7,24.Corsair XMS3 1600 hz. Works best for gaming....Change your bios to F4 or f4g .Some bios don't work i've been told.I have tried these 2 and they work. :hello:  :sol:  :sol:  :sol:  :sol: 


about the bios... does F3 work? if not, how do i do the Qflash trick? i would like to know... and is 1.4 volt ok for full unlocked processor?
July 4, 2009 3:09:44 AM

Have to say i was pretty sceptical about this but....It works!
I have the Gigabyte MA790GP-UD4H and using the f3 bios.
I set the ACC to hybrid and auto and when i rebooted it now says that its a phenom x4 20, now none of the temp monitor programs that i have will show a valid temp but i definately have four cores working and seemingly stable at 3.5gig (just changing cpu multi to 17.5) and no other changes at all!
July 4, 2009 11:43:03 AM

Well damn ! I have the same board and i cant unlock my 4th core. I must have one of the cpu's made after march 4th. I have tried just about everything. Hybrid ECC with auto ACC- all cores. per core. even tried going 0% up to +4 % down to -4%. I just got unlucky. Oh well. Im stable at 3.717Mhz at 1.408 voltage. Wish i could get that damn core to unlock though.
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a b K Overclocking
July 9, 2009 4:19:34 PM

MykC said:
You need a 790GX chipset and apparently the BioStars are the best for unlocking.

If your computer didn't boot you would just have to clear the CMOS and restore default BIOS.


Umm.. 790GX is not a chipset, its the name of the northbridge / SB750 is what you need (ACC) in order to unlock and Biostars are not the best for unlocking.. To my knowledge they are low end boards.. The top unlockers are Gigabyte UD3P's/Asus M4A79/MSI 790FX-GD70....
a b V Motherboard
a b K Overclocking
July 9, 2009 4:23:42 PM

remotehugger said:
Well damn ! I have the same board and i cant unlock my 4th core. I must have one of the cpu's made after march 4th. I have tried just about everything. Hybrid ECC with auto ACC- all cores. per core. even tried going 0% up to +4 % down to -4%. I just got unlucky. Oh well. Im stable at 3.717Mhz at 1.408 voltage. Wish i could get that damn core to unlock though.


Well not all 720's will unlock the 4th core. Its basically a 50/50 chance as far as the 720's. The x2 550's have a higher unlocking rate 80-85%....
July 9, 2009 4:26:33 PM

I have the Gigabyte MA790GP-UD4H with the SB750 and i just didnt get lucky unless there are other things i can try. I havent looked at the manufacturing date of cpu so i dont know if its one of the few or not. But i have seen a few people with my board that have been able to unlock 4th core. I just dont think there is anything else i can try. I have the F3a bios. Is there a wasy i can knock it back to the F2 bios? I've seen people have alot of luck with that version.
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a b K Overclocking
July 9, 2009 4:33:21 PM

I dont think your 720 will unlock if you have already tried the F3a bios. Check to see if there is a new bios version and flash, thats all I can recommend for now.
July 9, 2009 4:41:02 PM

thanks OvrClkr. I will check for a newer bios. I think im just out of luck. Im sitting at 3.6 stable on 3 cores so im not too dissapointed right now.
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a b K Overclocking
July 9, 2009 5:05:13 PM

Dude, 3.6 stable (3 cores) what more do you want? Thats sweet... Dont worry about unlocking the 4th core. I bet you dont even max out those 3 cores unless you are doing some mad rendering or cinebench.

As far as gaming is concerned your 720 at 3.6 should be more than enough.
July 9, 2009 5:13:09 PM

That is all i do is gaming pretty much. A little bit of home movie making but not much else. Thank you . This is my first build so im pretty happy. I just found out that the EPP on my OCZ DDRII 800 memory lowered my timings to 4-4-3-15 and boosted it up to 412Mhz with no errors with 100% coverage on memtest too. Woohoo:) 
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a b K Overclocking
July 9, 2009 5:38:54 PM

That is correct, EPP in bios works wonders for gettin the most out of your ram. The only thing I would do as far as your ram is : go into Bios and change the 3 for a 4 meaning you should end up with 4-4-4-15. That should be the most stable setting as far as your OCZ ram goes....Let me know if you need any help....
July 9, 2009 5:45:21 PM

Thanks again. I will change it right now. Would 4 more gigs do me any good ? I was thinking about getting 2 more sticks. Or should i consider 1066 ram ?
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a b K Overclocking
July 9, 2009 6:00:00 PM

Ok so here is the deal, if your OS is 64 bit then YES you should upgrade to 8 gigs, if not then 4 gigs is basically the max you can use on a 32 bit system. As far as 1066Mhz ram, i would not invest 60-80$ just to bump my speed up a tad. 4 GB of 800MHZ ram should be fine. If you have the money to burn then go ahead but you wont see a night and day difference. I would save up for a future build and then get some DDR-3. I have 667, 800 and 1066 ram and I do see a significant difference when we compare 667 to 1066 but from 800 to 1066 you really wont be amazed at the speed diference.
July 9, 2009 6:05:22 PM

I do have Vista 64. And i can 4 more gigs of the same ram for 40 bucks. And a future build is definitely coming so i think i will take your advice. I have very much enjoyed the experience and am looking forward to building another. And everyone on Toms have been great with me from the begininng. I had some pretty noob questions when i started. Thank you for your input.
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