Phenom X4 9850

Josh Collins wonders whether Phenom’s finally come of age.

The last time we took a look at a quad-core from AMD it was the Phenom X4 9900. Coincidentally, that chip never actually made it to the retail public circulation, and neither did the X4 9700. So, with the X4 9600 sitting at the top of AMD’s pile for some time, trotting along at a rather disappointing 2.3GHz and being eaten alive by the majority of Intel’s offerings, there wasn’t much to make it attractive. Being based on the B2 stepping with the Translation Lookaside Buffer (TLB) erratum – commonly referred to as erratum 298 – there wasn’t a whole lot to feel thrilled about in the Phenom corner. Hell, the whole AMD camp was looking lacklustre.

This month sees something of an AMD rebirth, or at least a string of new releases hitting with a bit more oomph than we’ve seen in the past 12 months, with the refreshed B3 Phenom X4 quad-core processors, newly released Phenom X3 triple-core processors, nForce 780a based motherboards, AMD 780G based motherboards and the new Athlon X2 4850e. It’s an all round AMD lovefest.
So what’s new? That is, other than the new products themselves.

Well, first up, the B3 stepping refresh fixes erratum 298 for the Phenom X4 range. This is denoted in the model number scheme by a five in the tens column; i.e. 9850. As was predicted back in our X4 9900 review in issue 85, this refresh has hit on time in Q1 of 2008.

Next is a speed increase. Although we saw the X4 9900 part running at a stock 2.6GHz, the new X4 9850 that has been publically released operates at a stock 2.5GHz frequency. This may be 100MHz less than the X4 9900 but it also has a stock TDP of 125W – that’s 15W lower than the 140W TDP of the unreleased X4 9900.

As the new top dog, and like the unreleased X4 9900, the X4 9850 sports a system bus frequency of 4000MHz, compared to the 3600MHz frequency of the second in line X4 9750 and old top chip the X4 9600.

What’s also new is the overclocking capability of the B3 chips. It appears both from our own testing, as well as perusing the overclocking results on HWBot, that these chips are allowing up to an extra 100MHz to 300MHz headroom over the maximum overclock compared to B2 chips. While the direct difference in final overclocks between our X4 9900 and X4 9850 sample was only 100MHz (3.15GHz compared to 3.25GHz), the effort taken to achieve the overclock has been vastly improved. In the past it was like pulling teeth – thank god it’s better now.

For starters, we started by simply raising the multiplier, as in our last round with the X4 9900 proved this to be the best overclocking method rather than raising the HTT frequency. Doing so, we got a stable 3.2GHz (200x16) before hitting a brick wall. The 16.5x and 17x multipliers resulted in either a BSOD or an endless BSOW (Black Screen of Wait for those uninitiated to Vista). Still, the system felt like there was more left; all we had to do was find it.
So we gave HTT overclocking a go. Interestingly, we ended up with a maximum HTT frequency of 263MHz – a marked improvement on the 235MHz max of the X4 9900. Settling on 260MHz HTT with a 12.5x multiplier for the max outright frequency, we still found the previous max of 3.2GHz (200x16), using purely the multiplier, to be more stable.

At the end of the day, it feels like there could be a reason to by an AMD Phenom X4-based system now. Ultimately though, the Core 2 Quad range from Intel still smashes the Phenom X4 range into submission. At least, now, you can be a fanboi with a little bit of pride.