October 9, 2001

Review: AMD Athlon XP 1800+ (1.53GHz)

Author: JT Smith

- By Jeff Field -
A few years ago, Cyrix, now part of VIA, released a line of CPUs called the 6x86. Cyrix claimed that these CPUs were equivalent to Intel CPUs of a higher clock, and labeled them as such with "performance ratings," PR ratings for short. Cyrix was criticized for this, because the CPUs didn't really outperform higher clocked Intel CPUs. We have been without PR ratings from the major CPU makers for the last few years, but now again we find them in use, with the new Athlon XP line of CPUs.

PR ratings: The next generation
The first time PR ratings were used, by Cyrix, they were somewhat fair -- the CPUs beat or equaled Intel CPUs some of the time, and were in other ways slower. However, since the release of the Pentium IV, AMD has had a problem. AMD's CPUs easily matched or beat Pentium IV CPUs at higher clock speeds. However, Intel had the upper hand in marketing. You see, the average consumer doesn't understand latency, pipelines, and other things that determine the speed of a CPU. For the most part, most consumers cling to a principle that just doesn't work anymore -- higher clock speed is faster and better. If one chip runs at 1530MHz, and another runs at 1800MHz, most of them will pick the higher clocked CPU. This put AMD at a disadvantage in the minds of consumers.

In order to fix this problem, AMD has chosen to make the move back to PR ratings for its CPUs. This latest AMD CPU, the Athlon XP 1800+, runs at 1.53GHz, yet it performs much faster than a Pentium 4 at 1.7GHz. So its fair game to label it an 1800+, because it really does perform that well, and is in fact a bonus to consumers, rather than burden -- because by purchasing an AMD processor they can, in most cases, save money, and get better, or at least equivalent, performance.

PR ratings aren't the only new marketing devices AMD has chosen to use with the Athlon XP. The name itself is a take on Microsoft's latest version of its flagship operating system. The Linux user in me thinks this is pretty annoying, and yet the reporter in me knows that this move is very good for AMD on the marketing front. If the average user's computer will run Windows XP, and he sees an Athlon XP, he's going to make the connection. NewsForge night editor David Graham came up with one solution -- "I can't believe they called it the Athlon XP. I say we call kernel 2.6 Linux XP" -- an interesting solution, although I think Microsoft might have something to say about it.

The chip
As far as the internal difference between the Athlon XP and Thunderbird 1.4GHz, they are the same as the differences between the Duron Morgan and Spitfire cores, which I explained in my Duron Morgan review. The XP, based on the Palomino core, adds hardware prefetch, which enables the processor to attempt to figure out what data it will need next, and grab it from memory, so the data is already waiting in the chip's faster cache memory. It also adds 3Dnow! Professional and SSE support. SSE is Intel's SIMD instruction set, which is supported by many applications. By including these instructions and setting the bit that identifies the Athlon XP as an SSE capable processor, AMD has enabled the Athlon XP to better run software optimized for SSE. In some operating systems, you must reinstall in order for SSE to be detected, if upgrading from a non-SSE chip. In the case of Linux, however, this is detected automatically, as can be seen by doing 'cat /proc/cpuinfo' at a shell.

The CPU core, as a result of the addition of SSE and hardware prefetch, grows by 500,000 transistors, to 37.5 million. Also, there are differences in packaging between the Athlon XP and the Thunderbird-based Athlons. The new Athlon XP uses what AMD calls an organic pin grid array, which uses fiberglass, similar to that used on printed circuit boards. Using this packaging lowers impedance and costs less to manufacture. It is also noticably thinner and lighter than the ceramic used in the Thunderbird-based Athlons.

System Specifications
AMD Athlon 'Thunderbird' 1.4GHz or AMD Athlon XP 1800+ 1.53GHz
256 Megs PC2100 DDR SDRAM from Crucial.com
Gigabyte 7DXR motherboard
Western Digital 7200 RPM 10.2 Gig Hard Drive
3Com 3C905TX-C 10/100 NIC (PCI)
400 Watt ATX 2.03 Power Supply
Gigabyte GF3000 GeForce 3 64MB AGP

Slackware 8.0 with Kernel 2.4.9 and XFree 4.1.0

Pentium IV Configuration, same as above except:
Pentium IV 1.7GHz (Socket 423 Model)
512MB RDRAM Memory from Kingston
Gigabyte 8TX Motherboard

Kernel compiles
In order to test both the board's stability and speed, I ran three sets of Linux kernel compiles on this board. One is a normal, "uniprocessor" make, or make -j1, which is the default. This uses one process, and does not always maximize system usage. I then did make -j2, which spawns a second process. The last test I run is with make -j3, spawning two extra processes. I do this for several reasons -- to find the "sweet spot" for the board/CPU, as well as to stress the system
as much as possible when trying to rate its stability. Also, the kernel is extremely useful as a measure of integer performance. In order to compile the kernel, I untarred kernel 2.4.6, ran "make config" and used the default values.

Kernel 2.4.6 Compile Times (Minutes:Seconds)
Lower numbers are better
Board -j1 -j2 -j3
Athlon XP 1800+ 1.53GHz 3:26 3:24 3:28
Athlon Thunderbird 1.4GHz 3:37 3:48 3:41
Pentium 4 1.7GHz 3:47 3:40 3:38

Here we see even the "old" Athlon 1.4 beating the Pentium 4 in -j1, and the Athlon XP beating it by an even wider margin. Performance like this makes AMD's case for PR ratings clear. AMD's CPUs easily outperform higher clocked Pentium 4 CPUs in compilation.

POVRay benchmarks
POVRay is a multi-platform raytracing program. It is a floating point intensive task and serves well to help measure the floating point performance of a CPU. For more information on this benchmark, head to the official POVBENCH homepage. The command to run for this benchmark, once you obtain POVRay, you run povray -i skyvase.pov +v1 +ft -x +mb25 +a0.300 +j1.000 +r3 -q9 -w640 -H480 -S1 -E480 -k0.000 -mv2.0 +b1000 from the command prompt. Results are in seconds.

POVRay (seconds)
Lower numbers are better
Board Result
Athlon XP 1800+ 1.53GHz 15 seconds
Athlon Thunderbird 1.4GHz 16 seconds
Pentium 4 1.7GHz 23 seconds

Here we see, first of all, the SSE doesn't matter much to POVRay, as the Athlon/Athlon XP score only seems to gain from the increase in clock speed. Here we also see the poor performance of the Pentium 4 floating point unit compared to the Athlons, a real turn-around from AMD's K6 line, which were plagued by their FPU performance.

Distributed.net client benchmark
Distributed.net is a distributed computing network that works on various distributed computing contests. The contests use primarily integer numbers while performing their tasks, and therefore serve as an excellent benchmark for overall integer performance of properly optimized software.

Distributed.net Client Benchmarks
Higher numbers are better
CPU RC5 Core 6 OGR Core 0
Athlon XP 1800+ 1.53GHz 5,419,596 keys/sec 11,539,041 nodes/sec
Athlon Thunderbird 1.4GHz 4,967,963 keys/sec 10,500,867 nodes/sec
CPU RC5 Core 8 OGR Core 0
Pentium 4 1.7GHz 2,439,327 keys/sec 7,342,364 nodes/sec

While most people don't consider Distributed.net when deciding what processor to buy, it provides us with an interesting look into the performance of an Athlon versus a Pentium IV. The Distributed.net picked the best core for RC5 on the Pentium 4 and Athlons, and we see the Athlon/Athlon XP beating the P4 by about 100% here. However, direct comparison between cores may not be fair, which is where OGR is useful. The OGR core is the same for both CPUs, and we see the Athlons doing roughly 50% more nodes than a P4 which the same code, nicely illustrating the difference between the two.

The Athlon XP nicely does the job of being a successor to the very successful line of Thunderbird-based Athlon processors. While not a technological flying leap over its predecessor, it adds a few key features while retaining the performance and reliability of the Athlon. Combined with the right chipset, and DDR memory, the Athlon XP has killer performance, and at a low cost. It clearly outperforms higher clocked Pentium IVs, and will soon be available for prices much lower them after inevitable price drops.

The Athlon XP 1800+ is available in lots of 1000 for $252 per CPU, and should be available in single units for slightly more than that. For those who need to upgrade right now, I would suggest the Athlon 1.4GHz, still a great CPU and available through Pricewatch vendors for around $99. The price for the XP should drop fairly rapidly however, so I would suggest some patience for those who wish to upgrade without spending a few hundred dollars. Also available are the 1700+ (1.47GHz), 1600+ (1.4GHz) and 1500+ (1.33GHz) available in lots of 1000 for $190, $160 and $130 per CPU, respectively. The best deal out of the bunch may end up being the 1.47GHz Athlon XP 1700+, which is about $60 less than the 1.53GHz 1800+, and only 60MHz slower. Also, Pricewatch lists the 1800+, 1600+ and 1500+ at $225, $148 and $122. The 1700 was not mentioned.


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