A: Phenom is designed as a Socket AM2/Socket AM2+ chip and should, therefore, drop right into the majority of existing motherboards, provided the motherboard maker updates the BIOS—and didn’t screw up on the board design (see our sidebar).
A: No. AMD corrected the issue that limited the DDR2 Athlon 64s to whole-number RAM divisors. This, in essence, would force DDR2/800 RAM to run at DDR2/766. Phenom CPUs use a separate clock for the memory controller, so memory will run at its intended speed. Consequently, however, the memory controller no longer runs at the core’s speed. The memory controller on the 2.6GHz Athlon 64 FX-60 runs at 2.6GHz. On the 2.6GHz Phenom 9900, the memory controller runs at 2GHz and notches down to 1.8GHz for the 2.3GHz Phenom 9600. It’s not clear if or how this impacts memory performance; it’s still a good clip faster than what the memory controller runs at in competing Intel machines, where that part is located in the north bridge.
A: First, every CPU released, and probably every piece of silicon, has bugs. Companies call them “erratum.” However, there are bugs and then there are bugs. In the case of Phenom, a last-minute big mutha of a bug was found in the translation lookaside buffer (TLB), a small cache used by the CPU to manage memory. AMD says that under very heavy workloads, such as in virtualization, the TLB bug could cause the system to hard lock. The company initially said the TLB bug was the reason it pulled the 2.4GHz and 2.6GHz Phenoms from launch but later recanted the statement, citing the aforementioned yield and volume issues.
A: A fix can be made through the BIOS, and AMD has informed board vendors how to implement the workaround. How much the BIOS change affects performance is hard to say. We, unfortunately, could not test the TLB patch, as it’s unclear whether our BIOS had the workaround implemented (we suspect it did not). Furthermore, AMD is forbidding board vendors from letting users toggle the workaround on and off in the BIOS. The website Techreport.com tested boards with and without the patch and reported that, depending on the test, the performance decline with the patch was anywhere from 0 to 60 percent.
A: AMD says the bug is so esoteric that it is unlikely to lock the system. That’s why the company is pledging to let you toggle the patch on or off in a future update of the company’s Overdrive application. We must point out, however, that the bug is severe enough that AMD is reportedly delaying a ramp up of quad-core Opteron sales until it has a silicon-level fix, which won’t be until later this year. At that time, AMD will also release a 9550 and 9650 with updated silicon.
A: We don’t know. We can say that the first Phenom CPU we received ran at only a third of the performance of an equivalent Intel CPU. That chip eventually went back to AMD for examination and we received a second CPU that performed more to our expectations. We tested the chip at various clock speeds and did experience two hard locks that could not be explained. We can’t say if the lockups were related to the TLB bug or simply immature drivers and BIOS. It does make us wonder if this problem is more serious than AMD has stated.
A: As old Ben said: “That depends on your point of view.” Because the 2.6GHz Phenom 9900 won’t ship until the winter begins thawing out, AMD will have updated “B3” silicon in place, and the performance numbers you see for the current chip should be representative. Of course, if you bought the Phenom 9500 or 9600 the day they came out, the performance numbers you achieve will likely be out of sync with those in most reviews, which were likely conducted without the fix in place. If, however, AMD is right and it’s very difficult to run into problems, you can simply flip off the TLB fix (when the updated Overdrive app is available) and get performance closer to what you’re seeing in reviews for the 2.3GHz part.
A: You’ll have to read our final benchmark report for the full verdict on performance, but the short answer is no. While the chip was close in some tests, AMD’s fastest Phenom, which won’t even be available for another few months, generally lags behind Intel’s midrange 2.66GHz Core 2 Quad Q6700 chip. Mind you, that’s virtually the same CPU Intel released more than a year ago using its older process technology.
A: AMD is spinning the Phenom story two ways: The first is that people need to stop thinking of CPUs as singular entities. Phenom, so it goes, is part of the Spider platform, which includes the quad-core CPU, AMD’s new 790FX chipset, and the Radeon HD 3870 GPU in CrossFireX mode—four cards running in tandem (see the sidebar below). Sure, AMD screwed the pooch getting Phenom clock speeds up and yields higher, but would you rather spend $2,000 on just a Core 2 Extreme and 2GB of DDR3 or a reasonably performing Phenom with four Radeon HD 3870 cards in it? Four!! AMD’s alternate spin is that, yes, it lags behind Intel today, but it’ll be back in the game eventually.
A: Until we actually test four Radeon cards in a box (no drivers were available to do so at press time), we can’t give you a definitive answer, but we’re not sure it’s actually enough to beat two GeForce 8800 Ultra (or even GTX) cards when combined with Intel’s fastest Core 2 Extreme CPUs. And in all things other than gaming, the Intel system will easily outclass the Phenom 9900. So we’re pretty skeptical about such a configuration outboxing an SLI/Core 2 Extreme box.
A: It will vary from chip to chip, of course, but Phenom is not shaping up to be a great overclocker today. We didn’t get very far with our engineering sample chip and few other reviewers have either. And when you look at how the thermals ramp up for relatively minor speed increases, it’s no wonder. Going from 2.3GHz to 2.4GHz takes the thermals from 95 watts to 125 watts. Going from 2.4GHz to 2.6GHz jumps it up to 140 watts. Older AMD and many Intel enthusiast parts have high thermal ratings but only because they’re anticipating users to overclock the hell out of them. We suspect that the increased thermals for the two faster Phenom parts are more related to AMD’s issue at the fab.
A: AMD tells us that it absolutely has not given up on the high end. Again, the company fully admits that it blew it on the Phenom clock speeds and yields, but says it is committed to turning the situation around. When that will happen isn’t known. It might take until the company’s 45nm process is online sometime this year or next to become competitive.
A: The tri core is being sold on the concept that if two is good and four is great, three is a perfectly attractive middle option. AMD’s tri core is primarily aimed at people who don’t want to pay for quad core but want some additional performance at a more affordable price. The CPUs are, as you might suspect, dies that won’t pass muster as quad cores but work fine with one core turned off. While some view this as selling defective chips, AMD says it’s business as usual. In the past, if a portion of a CPU’s 1MB L2 was bad, it could be sold as a chip with 512KB or 128KB L2, with the offending portion turned off. Like the higher-clocked Phenoms, the tri cores won’t be out until later in the year—they will carry model designators of 7 instead of 9. Since they’re the same chip as a quad core but with one core turned off, you can expect performance to fall in between their quad- and dual-core brethren.
A: If you’re a performance or overclocking freak, no. Intel is ahead and even AMD says so. But for folks with an existing AM2 board that supports Phenom (see sidebar), the CPU is a very easy, relatively inexpensive upgrade that gets you performance beyond Athlon 64. That should give die-hard AMD fans some solace. You might also be interested in Phenom if you buy into AMD’s Spider platform argument, but that’s unproven technology at this point.
A: AMD’s next stop is 45nm, which it says will be online at the end of this year. There’s likely to be a shrink of the Phenom core with some enhancements to get the performance up, but AMD’s CPU code-named Bulldozer will be the next chip to truly take on Intel. Bulldozer, which is due in 2009, will be a multicore design, but AMD hasn’t revealed very many specifics. The problem for AMD is that Intel is expected to make another jump forward with its chip code-named Nehalem, which will adopt AMD’s on-die memory controller and chip-to-chip communication techniques and feature four cores per die and an improved version of HyperThreading. With two quad-cores glued together under the heat spreader, a Nehalem would have up to 16 cores (eight real, eight virtual) available to the OS.
Comments are closed on this article
Kromaethius
February 10, 2008 at 9:48pm
Just built one and it's noticeably slower in all my tests against my Intel beastie. Yup, I'll stick with Intel's "True Power" vs AMD's "True 4 Core" any day.
dc10ten
February 19, 2008 at 12:12am
You may stick with "True Power" but intel is banking on "true 4 Core" Hence the reason they are moving it all on one die with Nehalm. Plus they are implementing a memory controller on the CPU. I wonder what other ideas intel has used from AMD...
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