ASUS M4A89GTD Pro/USB3 AMD 890GX Socket AM3 Motherboard Review

ASUS Features
As with all Asus motherboards, the M4A89GTD Pro/USB3 contains far too many features to discuss in a review.  This time I will highlight a really cool one that I haven’t seen  before.

Asus Core Unlocker:
If you weren’t aware, many AMD processors are merely higher series processors with various features disabled…for whatever reason, the CPU did not meet AMD’s standards for a particular model, but runs fine with certain features disabled, part of the L3 cache disabled, the clock speed lowered, etc.  AMD has been doing this for several years, their Sempron line has always been comprised of these CPUs.  It is a cool way for them to bring savings to their customers that don’t require the “top of the line” processor, and they get to recoup some of the cost rather than destroy these processors.

One of the possible “disabled features” is the disabling of one or more cores on their multi-core processors.  The Phenom II  X3 line is entirely made up of X4 CPUs with one core disabled, the Phenom II X2 line has two cores disabled.  The “Zosma” line of Phenom II X4s are actually Thuban X6s with two cores disabled.

Core unlocking was actually accomplished on earlier AMD chipsets with 700 series Southbridge which had ACC, or Advanced Core Calibration.  This capability wasn’t advertised, but I don’t suppose you could call it a “well kept secret”.  I guess I really didn’t pay attention, though I had a few 700 series boards but no processor that required unlocking. This capability was removed from the 800 series chipsets, much to the chagrin of those that had been aware of the capability.  (unlike most, I will not criticize AMD for that…they disabled the cores for a reason)

Asus has replaced ACC core unlocking with a new Hybrid feature called Core Unlocker.  Flip a switch on the motherboard, enable the feature in the BIOS, and you now have the capability of unlocking disabled cores.


Activate Core Unlocking by turning off the rig, flipping the Core Unlocker switch (located on the upper forward corner of the motherboard, it is the uppermost switch) and turning on the system.  An LED near the switch will light up when the Core Unlocker switch is activated.  Turn on the rig, and enable Core Unlocker by either pressing “4” during POST, or entering the BIOS and enabling it in the Advanced CPU Configuration submenu.

NOTE:  Be aware that core unlocking is very much like overclocking and should be seen as a plus rather than something that is expected.  AMD disables cores for a reason.  It is a subjective thing, not all processors will allow cores to be unlocked, and processors that will allow cores to be unlocked may not allow unlocking on all motherboards.

Unlocking a Phenom II X3 processor:
Unlocking a Phenom II X3 is a little less involved than the other models since you have only one core to unlock.  It is pretty much a matter of either it unlocks or it doesn’t.  The symptoms of a failed unlock are exactly like those of an unsuccessful overclock, ranging from failure to POST, to failure to launch Windows, to Windows launching but the system is unstable.  The tweaks are also exactly the same, raising VCore and CPU/NB voltage, and lowering the clock rate.

If Windows launches, you probably want to start the Task Manager to see if the unlocked cores are running.  CPUZ may call the processor by its locked name (i.e., Phenom II X3 720) or by an unlocked name (i.e., Phenom II X4)  You probably want to play around some to make sure the system is stable, do some benchmarking or serious gaming.  Running Prime95 overnight with small SSTs will usually find instability if it is there.

If the system will not POST, if the system does POST but Windows will not launch, or if Windows launches but is very unstable, you can do some tweaking to  try to get better results.  First, incrementally increase the Vcore.  Since the increments are so small with this board I’d probably do a couple of increments at a time up to the point of mere system instability.  Keep in mind that increasing the CPU voltage will heat up the processor, I highly recommend aftermarket cooling.  If you haven’t gotten results by the time you get to 1.4v, Vcore alone probably won’t do the trick.  (If your problem was failure to POST, you will need to turn off the Core Unlocker switch to get into the BIOS each time until the system will POST)

ASUS M4A89GTD Pro/USB3 AMD 890GX Socket AM3 Motherboard

So next, take note of what the CPU/NB voltage is, and incrementally increase it.  I’d probably back off the VCore to 1.375 or thereabouts. If you haven’t gotten satisfaction by the time you get to 1.25v-1.275v, you probably aren’t going to be able to unlock that particular CPU.  I was unable to unlock my Phenom II X3 720, only once did I get to the point of Windows trying to launch, every other time it bluescreened at the point of Windows beginning to launch.

Finally, I tried underclocking the CPU.  Yeah, I know, but an extra core is worth at least some underclocking.  After dropping the CPU speed a couple hundred mHz with absolutely no change, I decided that this core would not unlock.

ASUS M4A89GTD Pro/USB3 AMD 890GX Socket AM3 Motherboard

Unlocking a Phenom II X2 or Thuban X4 CPU (CPU Core Activation):
Unlocking Thuban X4s or Phenom II X2s are basically the same as the X3, excepting the fact that you are attempting to unlock two cores rather than one.  Normally that would mean an increased failure rate, but Asus already has the solution for that.  In the CPU Configuration menu in the BIOS, you also have a setting called “CPU Core Activation”.   This setting allows you to choose which cores you want activated…rather than being limited to forced unlocking of two cores, you can disable one and unlock the other, in other words a bad core will not prevent you from unlocking a good one.

ASUS M4A89GTD Pro/USB3 AMD 890GX Socket AM3 Motherboard

I would probably make my first attempt with all four (or six) cores activated.  If the system failed to POST or Windows failed to launch, I would use the CPU Core Activation to work on one core at a time, increasing VCore and CPU/NB voltage as necessary.

Again, core unlocking should be viewed as an added bonus rather than a guarantee, just like overclocking. If you are able to enjoy some unlocked core goodness, you are fortunate.  If not, you still got your money’s worth, because you paid much less for your processor than its unlocked core big brother.