nRiTeCh
Oracle

Attention !! All proud owners of AMD Phenom II X3 720BE
This article will definitely give you all the info about the X3 720BE processor and its mysterious 4th core mysteries, now solved and further to unlock the 4th core.
So you may already be enjoying your 720BE's rig overclocked either with default Tri-core or might have unlocked it to a magical Quad!
We have been constantly hearing about the secret 4th hidden core which many among us might have already successfully unlocked and enjoying the newly owned quad core processor at just fairly cheap price (as compared to quads), but many others are still out there having no idea what this tri-core could churn into ...
This guide is for everybody and especially for owners of AMD Phenom II X3 720BE which puts light on some of its interesting facts on unlocking the 4th core & some know hows. It will further help you choose the appropriate combo for getting that EXTRA advantage which none of us can really afford to miss out.
Every processor has got its unique Batch/Serial/Stepping no. for identification resembling its manufacture date/week/year and location.
After unlocking you can verify in CPU-Z, under specification tab it will show AMD Phenom II X4 20 Processor as against AMD Phenom II X3 720 Processor. Another interesting thing of this 720BE is if you view it in CPU-Z, under Code Name it will either appear as HEKA or DENEB.
Not much I can say about them except in pure lines, Heka is truely a Tri-core in pure form while Deneb is a Quad-core and results show there are less Heka 720s than Deneb and when you unlock the 4th core "successfully", it turns your Heka into Deneb. The good thing is that each 720BE processor has a disabled 4th core which can be unlocked.
You can go from this,

to this !!!

But certain things to worry about :-
- Only certain 720BEs's can actually run this enabled 4th core.
- The 4th core might get enabled on many motherboards but only some of them carries the ability to actually enable/use it and run the system as normal. Either on some motherboards it may get unlocked but the system wont boot (no display or might hang on bios screen). On some it may unlock and boot normally to windows & further but the system cannot be OCed.
- Only some handful of motherboards are able to unlock the 4th core and run it at stable stock speeds or at stable OCed speeds.
By unlocking the 4th core you're also unlocking its L1 & L2 caches, so there's no robbing of any sort, since L3 is shared between all cores. Also, the 4th core indeed provides a substantial performance boost and by unlocking it you'll basically get a fully fledged AM3 x4 processor which is IMHO a lot better than current AM2+ x4 920 & 940BE's.
Unlocking the 4th core sounds exciting and yes why not. Lets see it how -
Following are the CPU Serials/Steppings/Batches that can unlock the 4th core of the Phenom II X3 720BE and be stable been a Quad and speeds overclocked thereafter.

Some only succeeded on certain combos.
- 0849 CPAW
- 0851 FPAW
- 0851 FPBW
- 0903 GPMW
- 0904 BPMW 0243
- 0904 CPCW
- 0904 CPMW
- 0904 DPCW
- 0904 DPMW
- 0904 EPEW*2
- 0904 EPEW*3
- 0904 EPEW
- 0904 EPMW
- 0904 FPMW
- 0905 FPMW
- 0906 EPMW
- 0906 FPMW
It was found that 720BE's with serial 'MW' are favourites esp. 0904 EPMW, 0906 EPMW, 0904 DPMW, 0904 FPMW, 0905 FPMW, 0906 FPMW, 0904 EPMW & 0904 DPCW series has acquired highest success rates if paired with right motherboard combo.
Read on the stories in the end to know more.
To enable the 4th core -
In your motherboard BIOS, check for ACC-Advanced Clock Calibration control option and set it to "Auto" and then reboot and see whether the 4th core has been unleashed. It may happen you get the 4th core unlocked and running but it wont get recognize in Task manager, AOD, Everest, CPUZ, etc.
ACC option is available in different BIOS options & categories & depends on make/model of the board and BIOS version. Apparently you may try using AOD AMD utility to enable ACC. It has been found that currently only 790 chipset motherboards can unlock the 4th core.
Lets have a closer look further -
In Biostar, ACC can be accessed under T-Series section in BIOS.

Biostar boards that unlocks the 4th core
- TA790GX3 A2+
- TA790GX 128M
- TA790GX 128M AM2+
- TA790GX XE
- TA790GX XE AM2+ (BIOS A78CM113.BST)
- TA790GX A3+
In Gigabyte, ACC can be accessed under MB Intelligent Tweaker(M.I.T) option in BIOS.

If you cant find ACC, then press 'Control + F1' keys on the MAIN Page after entering BIOS, the screen will flash, then go into the various sections to look for hidden settings. This trick only works on certain Gigabyte BIOS version like the F2D BIOS. Also, you may try updating your BIOS if none of the options work.
Gigabyte boards that unlocks the 4th core :
- GA-MA790GP-DS4H
- GA-MA770T-UD3P (F2C BIOS)
- GA-MA790GP-UD4
- GA-MA790X-UD4 (F2A BIOS)
- GA-MA790GP-UD4H (F1 BIOS)
- GA-MA790X-UD4P (F5/F5a BIOS)
- GA-MA790XT-UD4P
- GA-MA790FXT-UD5P (F3B BIOS)
DFI board :
- DFI LP DK 790FXB-M2RS
ASRock boards :
- AOD 790GX 128M AM2+
- ASRock M3A790GXH 128 AM3
Asus boards:
- Asus M4A79DX
- Asus M3A78-T (on BIOS ver. 'M3A78T-0023a.rom')
Many board manufacturers have removed or disabled the ACC option after pressure from AMD. AMD really don't want you to unlock that extra core, they want you to buy an X4. It may not even be possible with your board, but check out BIOS ver. to make sure. It might also happen that upcoming new 720BE's will have the 4th core permanently disabled.
As per VFM, Biostar is arguably the most preferred motherboard, a real VFM rich in features and having he highest success rates in not just unlocking but also running 720BE tri to a quad (either @ stock or OCed).
The stories & milestones so far - both successfuls & unsuccessfuls :
- 0849 CPAW Boot OK, and acts normal like Phenom X4.
- 0851 FPAW on ASRock AOD 790GX 128 AM2+,790GX/SB750 3.5Ghz 1.46v.
- 0851 FPAW 3.6Ghz on TA790GX 128M stable.
- 0851 FPAW n 0904 BPAW both on Biostar TA790GX A2+ (BIOS: 78DBA113) after turning ACC to Auto computer won't boot.
- 0851 FPAW on DFI 790FXB M2RS to 3.8Ghz going stable
- 0851FPMW can't enable the 4 core with DFI LP DK 790GX-M2RS.
- 0904 BPAW can't boot at all when ACC Enable, show F2 in debug card.
- 0904 BPMW the core unlocks but not stable at 2.8ghz.
- 0904 BPMW DFI 790FXB, enable to unlock the 4th core but can't get Prime stable.
- 0904 BPMW, Boot OK, detect as Phenom X4 and then stop, debug card shown 83 code.
- 0904 BPMW on stock 2.8Ghz Giga 790FXT F3B bios. Prime testing for more than 40min. in 4 cores @ stock.
- 0904 BPMW on Biostar TA790GX3 A2+ @ 3.2Ghz stable.
- 0904 EPMW on Asus M4A79DX @ 3.Ghz stable.
- 0904 EPMW on Biostar TA790GX XE (AM2+, 790GX/SB750) 3.5Ghz 1.45v. BIOS is A78CM113.BST stable.
- 0904 EPMW Biostar TA790GX 128M (AM2+, 790GX/SB750) 3.4Ghz 1.36v. stable.
- 0904 EPMW on Biostar TA790GX XE (AM2+, 790GX/SB750) 3.5Ghz 1.45v. BIOS is A78CM113.BST stable.
- 0904 EPMW Biostar TA790GX 128M (AM2+, 790GX/SB750) 3.4Ghz 1.36v.
- 0904 EPMW Asrock AOD790GX/128M (AM2+, 790GX/SB750) 3.5Ghz 1.4375v.
- 0904 EPMW Biostar TA790GX XE (AM2+, 790GX/SB750) 3.5GHZ 1.45vcore. BIOS is A78CM113.BST
- 0904 EPMW Biostar Tforce TA790GX 128M.Had to increase the voltage on the northbridge to resolve errors in Prime95 with large FFT's, Stable at 3.4ghz, 1.36v.
- 0906 EPMW on 3.5Ghz GA-MA790XT-UD4P stable.
- 0904 CPMW 4th core unlocks, but is unstable at any voltage.
- 0904 CPMW unable to load windows with 4th core enabled.
- 0904 CPMW on Asus M3A78-T/bios mod hangs.
- 0904 CPMW @ 3.5GHz stable.
- 0904 CPCW on GA-MA790GP-UD4H. It's been 30 minutes running OCCT stable at 3.6Ghz.
- 0904 DPCW GIGABYTE GA-MA790GP-UD4H rev. 1.0 BIOS ver. F1 @ 3.2Ghz stable 1.344v, stock volts, stock cooler. nice working.
- 0904 DPCW running all four cores. So far i'm at 3.2Ghz. Motherboard is a Gigabyte DS4H with F2 Bios.
- 0904 DPCW on Biostar 790GX @3.3 stable.
- 0904 DPCW, GIGABYTE GA-MA790GP-UD4H (AM2+, 790GX/SB750) 3.2Ghz 1.325v, rev 1.0 BIOS ver. F1.
- 0904 DPMW @3.8ghz 4 cores Prime 32M & 1024M on GA-MA790FXT-UD5P AM3.
- 0904 DPMW on Gigabyte MA4790FXT-UD5P @ 3.6 stable.
- 0903 GPMW GIGABYTE GA790FXT-UD5P @ 3.6 stable
- 0904 FPMW Biostar TA790GX A3+ @3.2 stable
- 0904 FPMW 3.6GHz TA790GX A3+
- 0904 FPMW Biostar TA790GX A3+ @3.6 stable
- 0905 FPMW 3.7 GA-MA790X-UD4P
- 0905 FPMW 3.7 stAble on Gigabyte GA-MA790X-UD4P with BIOS F5/F5A (they are the same).
- 0906 FPMW 3.7 stable on ASRock M3A790GXH/128M
- 0906 FPMW 3.7 ASRoCk M3A790GXH/128M
- 0906 was able to unlock the 4th core with the Biostar 790GX. Ran Prime95 for 7 hours on "Blend" and everything passed.
- 0907 unable to unlock on DFI JR 790 board with bios R7JD225A.
All 720BE users do post your configs and results here in following manner no matter if you have been successful or not. We can come to know more about the combos and batches.
Model: X3 720
Serial: 0906EPMW
Unlocks 4thcore: Yes
Is it stable: Yes (11 hours 30 min on Prime95 stock clocks, and gaming TF2)
Max stable OC as X3 with Volts: 3.4GHz @ 1.325V with 6 hours on Prime and few hours TF2 stable
Max stable OC as X4 with Volts: 3.2GHz @ 1.3V --11 hours 30 prime95
Temps load/idle: 60c/44c
Cooling: Noctua NH-U12P
Board: GA-MA770T-UD3P (Bios F2C)
Model: X3 720
Serial: 0904EPMW
Unlocks 4thcore: Yes
Is it stable: Yes
Max stable OC as X3 with Volts: Not attempted
Max stable OC as X4 with Volts: 3.4GHz, all 4 cores at 3.4 stock volts
Temps load/idle:
Cooling: Stock
Board: GA-MA790X-UD4P
and this one by far the greatest achievement :

You can add more to the list only if you find something really different, thus avoiding duplicates and keeping this thread clean.
Ref : Before starting, I referred many websites but cant put each of its names here but I do thank them all without which it wouldnt had been possible to write this article. Whatever info I have given here is to the best of my knowledge and so also of the websites referred and thus data collected and arranged here.
To name a few, I will thank Google, XtremeSystems.org and overclock.net.