AMD and Intel have recently launched faster frontside bus processors and paired them with dual-channel DDR. John Gillooly discovers what impact this will have on the ongoing performance war.
Atomic has visited the Athlon vs. Pentium 4 battle several times in the past as these CPUs evolved into the beasts they are today. Initially the Willamette Pentium 4 performed at a level much lower than the Thunderbird-cored Athlon, a gap increased by AMD when it released the Palomino and its PR rating scheme for CPU labelling. This was an attempt to blur the boundaries between the high frequency but relatively low performing Pentium 4 architecture, and the more frequency efficient Athlon architecture.
ABOVE: On top is ASUS' A7N8X Deluxe version 2 motherboard, which is based around NVIDIA's nForce2 Ultra 400 chipset. Below that is ABIT's IC7-G, which uses Intel's i875P chipset.
Intel struck back with the Northwood core for the Pentium 4, dropping the die to a 0.13-micron process and upping the L2 cache to 512KB. This allowed the Pentium 4 to leap ahead of the Palomino and following Thoroughbred cores of the Athlon. AMD recently released its Barton core, with the same 0.13-micron process and 512KB of cache that made Northwood so powerful.
Barton has culminated in a new 400MHz FSB model of Athlon XP, the Athlon XP 3200+, which operates at 2.2GHz. This is set to be the last major core revision before AMD debuts its much delayed Athlon 64 processor later this year. With the release of this chip we have taken the opportunity to get another snapshot of how the performance race between Intel and AMD is going, and see what effect the new generation of dual DDR chipsets has on performance.
This month's head-to-head is brought to you by dual-channel DDR, feature heavy motherboards and the number 200. Last month Intel introduced a 3GHz Pentium 4 running on a quad-pumped 200MHz bus (800MHz effective), and this month we see the Athlon XP 3200+ that uses a double-pumped 200MHz bus for an effective 400MHz FSB.
This has happened thanks to the gradual legitimising of DDR400, mainly through pressure brought by Intel to get the standard up and running without final JEDEC approval. Normally we would be reticent pushing a semi-official standard, the recent scaling back of 802.11g from 54Mb/s to 20Mb/s being a good example of changes that can occur at the last minute; however the sheer weight of Intel being thrown behind DDR400 means an almost assured success for the standard as it now stands.
These new CPUs have been performing at their peak thanks to some phenomenally fast chipsets. Intel launched its new flagship performer, the i875P and NVIDIA has launched a new nForce2 variant of sorts, the nForce2 Ultra 400. Both of these chipsets employ dual-channel DDR to maximise performance, however the theory behind dual-channel DDR varies for each platform.
Intel uses the technology to optimise the bandwidth of the P4's 800MHz bus. Two sticks of DDR400 running in dual-channel mode delivers the 6.4GB/s needed for the P4 to have maximum memory bandwidth.
The Athlon only has 3.2GB/s available bandwidth, which matches up with the 3.2GB/s delivered by a single-channel of DDR400 memory. This begs the question of why would bother with dual-channel DDR400 for the Athlon, when a single-channel will deliver all the bandwidth needed?
The answer is simple; it isn't just the CPU that needs direct memory access these days. Having an excess of memory bandwidth means that operations like texture access over the AGP port, and I/O operations requiring direct memory access will not compete with the CPU for memory resources, making for smoother system performance and higher benchmark results when the program is stressing multiple subsystems.
We have taken this into account in our testing. We've benched the 3GHz C model Pentium 4 against the Athlon XP 3200+ using a suite of benchmarks that can be split into two categories. The first is our usual CPU testing suite, and the second is a collection of game and application benchmarks designed to stress the system's memory bandwidth.
The Pentium 4 has been paired with an ABIT i875P based IC7-G motherboard, two sticks of Kingmax DDR400 and a GeForce FX 5800. For the Athlon XP 3200+ we have used the same RAM and video card, but we have chosen an ASUS A7N8X Deluxe version 2 motherboard based around the nForce2 Ultra 400 chipset.
For our CPU testing we have included results from the notoriously Intel-focused SYSmark2002, and the pure bandwidth testing of Quake 3: Arena. The results are included not only for consistency, but also to show that there are factors influencing system performance above and beyond simple CPU grunt. Both of these tests show clear victories for Intel, with a 26% lead over the Athlon XP in SYSmark2002 and an 18% lead in Quake 3: Arena.
However these trends do not carry over into actual system performance. 3DMark2001SE Pro shows the Pentium 4 system coming out 5% faster than the Athlon, which is the biggest lead that Intel has in the system wide tests. In Unreal Tournament 2003 the Athlon XP is neck and neck with the Pentium 4, a trend repeated in Codecreatures where there is less than a frame difference in each test.
SPECviewperf is a professional graphics benchmark and perhaps the best stressor of all the subsystems. In viewperf the results are generally consistent except for the vertex-heavy DesignReview viewset test (drv-08), where the Athlon XP leaps ahead.
Again we see despite the marketing and branding shenanigans, and the huge clock speed disparity, there is little overall difference between the high-end products from Intel and AMD. There are still architectural differences, and Intel would argue that the inclusion of Hyper-Threading is a performance booster, even though tangible performance gains are rare with this very young technology.
However for raw across-the-board performance the gaps just do not exist.In the past the decision between the two CPUs would have been a no-brainer. Historically AMD's top-end CPUs have been much cheaper than Intel's. However we did some searching around on prices, as the US dollar price in one thousand unit lots that is quoted by chip manufacturers is usually irrelevant when it comes to retail pricing. All the prices we saw had the Athlon XP 3200+ sitting at around $900 while the 3GHz C model Pentium 4s were sitting in the low $800 range. Intel has also flowed its 800MHz FSB on to slower processor models, while AMD were yet to have anything other than a 3200+ running on a 400MHz FSB.
Our current tip would be to search out a lower-end D1-stepping Pentium 4 with an 800MHz frontside bus. These low-end models are cheap and are found to be highly overclockable. Until AMD flows the 400MHz FSB down to the lower speed models Intel has the advantage.
Issue: 137 | June, 2012