The Phenom 9600 Black Edition has been knocking around in Damage Labs for a while now, and I’m afraid I haven’t done it justice. The Black Edition is an intriguing product in a number of ways, because it’s a relatively affordable quad-core processor with an unlocked upper multiplier for easy overclocking. AMD has had its share of trouble with the Phenom, from delays to the clock frequency problems to the infamous TLB erratum, but the Black Edition is a very nice olive branch that AMD has extended to enthusiastsand it may warrant your consideration, especially if you’re already running a Socket AM2-based system.
My original plan was to publish a full-blown review of the Black Edition, complete with a full set of benchmark results for the processor both with and without the TLB erratum workaround enabled. As I’ve noted elsewhere, though, that’s actually happened already, since I included those numbers in my Skulltrail review. What you’ll find there are scores for the Phenom 9600 at stock speeds with and without the TLB workaround, along with our first power efficiency tests for the Phenom with Cool’n’Quiet dynamic clock throttling working properly. The results confirm our initial impressions of the TLB workaround’s impactit’s sometimes quite devastatingand illustrate that the workaround can degrade performance in games, as well. Even with the workaround disabled, the Phenom 9600 at stock clock speeds can’t quite keep pace with its most direct competitor, Intel’s Core 2 Quad Q6600, in terms of overall performance.
So we already have the stock performance picture for the Phenom largely covered. The Phenom 9600 Black Edition, though, remains one heckuva playground for tweaking and tuning. Let me briefly share with you some of my experiences with it, including my overclocking exploits.
OverDrive or BIOS?
If you’re using a motherboard based on AMD’s 790FX chipset, tweaking the Black Edition will probably start and end with AMD’s nifty OverDrive utility, although you may take a few detours in between.
The first thing most folks will want to do with OverDrive is disable the TLB erratum workaround. As we’ve explained elsewhere, AMD says the possibility of the erratum causing a crash doing the kinds of things that desktop PCs tend to do is very remote, and we believe them. If you’re already accustomed to risking some possible system instability by overclocking your CPU, you’re probably a good candidate for, uh, going commando and running without the TLB workaround. And, in truth, you’re not going to want to buy a Phenom right now, prior to the arrival of new chips with a proper fix for the erratum, unless you’re willing to run without the workaround. The Phenom’s performance with the workaround enabled just isn’t attractive.
AMD has recommended that PC vendors enable the workaround by default, which it surely felt obligated to do because consumers (rightly) expect “100% stability” out of a processor. The firm has also recommended that motherboard makers update their BIOSes to include the TLB workaround with no option to disable it. But AMD has left a loophole in its OverDrive utility, the one officially sanctioned place where users can disable the workaround.
Unfortunately, they’ve left it almost entirely undocumented. The button for disabling the TLB workaround sits in the top right corner of the utility’s main window with no labeling unless you hover the mouse pointer over it. Then you’ll see what’s shown in the picture to the right: “When this button is yellow or red, your system enters into boost mode.” That’s all you get. AMD tells us that what’s happening is this: whenever the button is yellow or red, the TLB workaround is disabled. When the button is red, the utility also disables a power management option on the CPU, which can boost performance a little bit more.
I don’t understand AMD’s approach here. If they’re going to provide a means of disabling the workaround, I’d think they’d want to be entirely clear with users about what the utility is doing and what the risks are. Heck, the rest of OverDrive’s tweaking options are incredibly detailed and clearly labeled, right down to the most obscure memory timing options.
I ran into another issue with OverDrive’s TLB workaround switch. I hesitate to mention it simply because I haven’t had time to investigate it fully, but it merits a mention. I tried using OverDrive to disable the TLB workaround during some of my performance testing, using Vista x64 and an MSI K9A2 Platinum motherboard, and I found that the switch didn’t always seem to work as advertised. Disabling the workaround via OverDrive generally yielded performance below what I could get by using a BIOS that didn’t include the workaround. In some cases, performance didn’t improve at all with the “Turbo” button in OverDrive set to yellow.
The good news is that mobo makers seem to be engaging in a bit of civil disobedience with regard to the erratum workaround. Asus provides a clearly labeled option for enabling and disabling the workaround in the M3A32-MVP Deluxe BIOS, and in the version of the BIOS I tried, the workaround was even disabled by default. Intriguing. On the MSI board, I completed my performance testing simply by flashing back to an older BIOS without the workaround. Later, I was able to hunt down a beta MSI BIOS on the Internets that includes a workaround switch, as well. Given everything I’ve seen, I think using a BIOS-based switch is the best means of disabling the workaround.
That’s especially true, of course, if you have a Socket AM2 motherboard that’s not based on an ATI/AMD chipset, since OverDrive won’t work on those boards. Since the Phenom’s launch, the upgrade prospects for current owners of AM2 motherboards have been cloudy, to say the least. As I write, AMD’s motherboard compatibility list for the Phenom includes 17 motherboards, and only five of them are based on Nvidia chipsets.
To test the waters, I flashed the BIOS on my Asus M2N32-SLI Deluxe motherboard, a mobo based on the nForce 590 SLI chipset that does not appear on AMD’s Phenom compatibility list. Asus has released a BIOS intended to support the Phenom, and for me, it worked like a charm. Interestingly, Asus did not include the TLB workaround in the version of the BIOS that I used. Also, for what it’s worth, this Socket AM2 board ran the Phenom 9600’s north bridge clock at 1.8GHzjust the same as on the AM2+ boards I’ve used.
Even more interestingly, although this wasn’t the case with our M2N32-SLI Deluxe, I understand Phenom support is a bit of a tricky affair in some Socket AM2 boards due to BIOS ROM size constraints. On some boards, Phenom support is possible, but the procedure for upgrading is to flash to a Phenom-compatible BIOS using an Athlon 64, shut down, and then install the Phenom. If you want to go back to the Athlon 64, you must first flash to an Athlon-compatible BIOS using the Phenom. Personally, I could probably live with that, but I have ready access to spare chips to swap in. Without that, this limitation really does raise the degree of difficulty for a CPU swap.
Cranking up the clocks
Once I was done futzing around with BIOSes and workaround stuff, I pretty quickly headed… well, right back to the BIOS for an overclocking attempt. I started out thinking I’d want to overclock the Black Edition primarily using OverDrive, since the utility has an auto-tuning feature that’s supposed to help seek out your CPU’s limits. However, after a number of system locks without making any real progress, I decided it was time to go old-school once more. I also decided to switch over to the Asus M3A32-MVP Deluxe motherboard for my overclocking attempts because its BIOS offered some options I wanted.
In this context, the OverDrive utility still proved quite useful thanks to its nifty built-in performance test that stress tests all four Phenom cores at once.
I’ve long used Prime95 for this task, because I like how it throws an error when it gets a wrong result, even if the error isn’t enough to cause a system crash. However, firing up four instances of Prime95 is a bit of a chore, and OverDrive makes it easy. You can even specify how long you want the stability test to run, which is nice. During the iterative steps of an overclocking attempt, just surviving a few minutes is good enough to confirm whether a particular setting is stable enough to justify moving on.
I started out using nothing more than a stock AMD cooler for the Black Edition. My first attempt was at 2.5GHz, or 200MHz above the 9600’s stock speed, with a stock 1.25V. The system would POST and boot into Windows at those settings, but quickly crashed. Bumping the chip up to 1.275V was all I needed to get the Phenom to pass a three-minute session in the OverDrive stability test, though.
So, I figured, it was time to move on to 2.6GHz. This is, after all, not unfamiliar territory. We have a Phenom engineering sample that will run fine all day at 2.6GHz. Surely this one would do the same.
The system would POST at 2.6GHz but hang before booting Windows. I tried upping the voltage to 1.3V and 1.325V, to no avail. At this point, frustrated, I began to doubt the ability of the stock cooler to do the job I was asking of it. Fortunately, I had the means to remove all doubt at my disposal, and so I did, by installing this:
That’s a Cooler Master Hyper 212, a cooler roughly the size of a human head.
Ok, maybe a smaller human’s head, not quite the equal of the jumbo-sized noggin on a hardware reviewer. But you get the picture.
I started with that cooler at 1.325V and still, the system hung shortly after POST at 2.6GHz. I tried raising the voltage as high as 1.3625V, but nothing changed. I even tried backing down to 1.3V and 1.2875V, hoping the additional cooling might work there, but no. This particular chip seems to have a pretty hard limit at 2.6GHz, unfortunately. I’m probably a wuss for not taking the chip to 1.4V and beyond, but I’ve found that increasing voltage usually only helps improve stability incrementally; this thing wasn’t even making it through the initial stages of the boot process.
I decided to call it good at 2.5GHz, and I took my official screenshot at that speed as incontrovertible proof of the clock frequency I’d achieved.
I wasn’t done there, though. As you may know from this page of our Phenom review, among other sources, the Phenom architecture’s memory access latency and overall performance is affected quite a bit by the speed of the chip’s L3 cache. That cache runs at the speed of the chip’s north bridge, not the CPU core clock, so there’s some real performance potential hiding in the Phenom’s north bridge clock. With just a little coaxing, I was able to get our Black Edition north bridge stable at 2.2GHz, or 400MHz above stock.
In order to demonstrate the impact of core and north bridge overclocking, I ran a couple of sets of quick benchmarks on the Black Edition: one with just the cores overclocked to 2.5GHz and another with the north bridge at 2.2GHz, as well.
So there you have it. At 2.5GHz with a 2.2GHz north bridge, the Phenom 9600 Black Edition is definitely more potent than at stock speeds, but the differences aren’t massive. Still, overclocking with an unlocked multiplier is dead easy, and when you’re finished, all of the system’s HyperTransport, PCI, and other clocks are still running at their stock, stable speeds.
Based on what we saw from our Phenom 9600 Black Edition, I wouldn’t expect to see astounding overclocks out of these chipsat least not all of them. Of course, overclocking headroom is never a sure thing, and you might have more success than we did. Never know.
I wouldn’t count on it, though.
With the apparently limited headroom in the Phenom at present, having an unlocked multiplier isn’t exactly a huge advantage. Happily, however, AMD isn’t charging extra for the Black Edition, and street prices between the vanilla Phenom 9600 and the Black Edition are roughly equal at around $259. Heck, the Black Edition is down to $239 at Newegg. Given that, if you’re going to buy a Phenom, this is definitely the one to grab.
Here are the things on my wish list from AMD: more clarity on how to disable the TLB workaround if you want to and broader, better-documented Phenom support for legacy Socket AM2 motherboardsespecially those based on Nvidia chipsets, which are almost surely the majority of the enthusiast-class motherboards in existing systems. I’d also like to see a utility for disabling the workaround that would work with non-AMD-chipsets. If we had those things, I think the Black Edition could be a tempting upgrade for a lot of Athlon 64 X2 owners who don’t want to bother with the hassle of a motherboard swap or an OS installation in order to get quad cores. Without them, today’s Phenoms are in a tough spot in a tremendously competitive environment.