Bennett Ring has chipped away, and uncovered a couple of overclocking gems.
While AMD’s CPUs continue to plummet further into the realm of unoverclockability (yes, that is a word), Intel’s CPUs march ever-towards tweaking nirvana. Two new CPUs from Intel, the 2GHz Celeron and the C1-stepping Pentium 4, are shattering the notion that we shouldn’t expect much of an overclock from today’s 2GHz+ CPUs.
The C1-stepping of the Pentium 4 has been setting the world’s overclocking forums on fire, yet only those who understand what a CPU stepping is know what to look for. A stepping is basically a revision of a CPU, with changes to the mask that is used in the process of creating the processor. The C1-stepping uses an entirely new mask, which means that it’s a major revision to the Pentium 4, and it just happens to be an extremely sweet overclocker.
This doesn’t mean that the C1 is a whole new chip -- it’s just a P4 that has undergone a bit of a facelift. With a little motherboard voltage modding and some extreme cooling, many people have reported overclocking the 3.06GHz C1 Pentium 4 up to a whopping 4GHz and beyond.
For the sane rest of us, to whom the idea of pouring liquid nitrogen into a brass cup over the CPU seems a little insane, not to mention impractical, the lower speed 2.2AGHz C1 and above CPUs have been averaging a maximum speed of between 3GHz and 3.5GHz.
That’s a massive overclock of around 1GHz with standard air cooling -- provided you can get your hands on a lower-speed C1, which are rarer than a hot chick at a Counter-Strike LAN. Check out the C1 table (kindly supplied by the chaps at www.overclockers.com) to identify if the P4 you’re about to purchase is actually of the C1 variety. An easier way to tell is to check the core voltage of the CPU; if it defaults to 1.525 volts, you’ve got yourself on hell of an overclocker.
We managed to get our mitts on a 2.4B GHz C1 -- unfortunately we couldn’t find a C1 with a 100MHz frontside bus. Which is a pity, as the final overclock we managed to squeeze out of this chip could possibly have been limited by the maximum frontside bus speed of the motherboard we tested it in. So just how much free speed did we manage to wring out of the 2.4B GHz?
We tested using an ABIT BG7 i845G-based motherboard, with some scrumptious Corsair XMS3500 DDR-RAM (scrumptious due to its max speed of 400MHz). A RADEON 9700 PRO was also used to limit bottlenecking in the graphics card department. After a mere 15 minutes of tweaking we managed to get the chip to run at 2.91GHz, with a front side bus of 162MHz (with a locked multiplier of 18x). Voltage was increased to 1.7V to get it to run stably, which is about as high as you want to go in the juice department without extreme cooling on a 0.13-micron Pentium 4. While it wasn’t quite as high as expected, a free 500MHz is still a 20% overclock. Thanks Intel.
As a result of this overclock, we managed to increase the UT2003 CPU test (the Inferno DM map running at 640 x 480) score from 201 frames per second up to 240 frames per second -- an almost exact speed increase of 20%. SiSoft Sandra CPU test scores also increased by almost exactly 20%, with a Dhrystone ALU score of 7475MIPS, and a Whetstone FPU/iSSE2 score of 1705/3903MFLOPS. Not bad for a $400 CPU running at the same speed as a CPU that will set you back at least $1,000 (www.pricewatch.com.au).
If you thought that was a nice overclock, just wait till you see what we managed to push the 2GHz Celeron to. How does a free 800MHz sound to you? Yeah, we thought a 40% speed increase was quite impressive too. Thanks to its default 100MHz front side bus, we only needed to increase the front side bus up to 140MHz, well within the range that the BG7 motherboard is capable of. However, the lack of cache still hobbles the Celeron, even when it’s running within a mosquito’s pecker of 3GHz. In case you’d forgotten, the Celeron has a meager 128KB of L2 cache, a quarter of the 512KB on the full-blooded Pentium 4. This has a tremendous impact on the CPUs performance, as instructions need to be fetched from the main system memory more often to keep the cache filled with relevant data. As a result, the 2.8GHz can’t really compete with equivalently priced AMD CPUs, with the closest in price being the Athlon XP 2000+. Unfortunately we didn’t have a 2000+ for comparison, so we squared it off against the Athlon XP 1800+, which is around $40 cheaper than the Celeron. Even though the AMD chip is clocked at a meager 1.53GHz, it still stomped over the Celeron, with a UT2003 CPU result of XXX frames per second, as compared to the Celeron’s score of 105 frames per second. Even when the Celeron was cranked up to 2.8GHz, it only managed to reach 151 frames per second, which is still inferior to the Athlon XP 1800+. So even though the Celeron is great at overclocking, it still can’t keep up with the equivalently-priced AMD CPU.
It’s amazing how much the tables have turned over the last 18 months or so. While it’s increasingly difficult to get anything free out of AMD’s Athlon, the reverse has occurred with Intel chips. While the new Celeron offers up to 40% extra performance free, it’s still a crippled chip, so it’s the C1 Pentium 4s that keen overclockers should keep their eyes peeled for.
Issue: 137 | June, 2012