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Written By:
Date Posted: January 24, 2001
Hot off the success of the Athlon Thunderbirds, Advanced Micro Devices began to feel the heat from chief competitor Intel. Although in the Thunderbird was able to keep up, if not surpass the performance of higher clocked Pentium 4s, it was only a matter of time before clock speed would make a difference. Compounded with the fact that As Thunderbirds got faster, be it by design, or by overclocking, they got hotter. As many should know, heat becomes a factor as the clock speeds increase, which ultimately caps a processor from reaching any higher.
Truth is, it wasn't just the heat, but the fabrication process needed an overhaul, and the architecture of the Athlon wasn't suited to reach such high clock cycles. The main difference between the two rivals, was AMD's Thunderbirds employ shorter pipelines, whereas Intel Pentium 4s used longer ones. I'm not going to get into specifics, since it's been drummed to death all over, but Pentium 4 CPUs can scale to higher frequencies then Thunderbirds.
Of course, knowlegable computer users understand that clock speed is not always indicative of performance. Unfortunently, the majority of shoppers don't know this. For one thing, Intel does have a lot of brand recognition, and it's likely Joe ComputerUser has heard of Intel, and not AMD. Secondly, and this is an opinion alert (!), AMD tends to sell their CPUs much cheaper than Intel does, thus giving it the appearance of a 2nd class processor. if Joe walks into a shop, and sees an Athlon 1.4GHz system for 600$, and an Intel 1.4GHz system for 800$, chances are, he'll "think" something must be wrong with the 600$ system, since they're both 1.4GHz. Finally, it's the clock speed issue. In most benchmarks, the Thunderbird 1.4GHz can more or less keep pace with the 1.7GHz P4. Sometimes AMD wins, other times Intel wins. Joe, on the otherhand, doesn't really care about benchmarks, and sees one is 1.4GHz, and the other is 1.7GHz, therefore the P4 is 300MHz faster.
AMD needed to find a solution(s) to the clock speed race. They needed to also do something to inform and educate the computer public that it isn't always clock speed that matters. The result? AMD introduced the Palomino, aka Athlon 4/MP/XP. The Athlon 4 is the mobile version, the MP is the workstation version, and the XP is the desktop version. Today, we're going to take a look at the Athlon XP 1800+ (1.53GHz).
Specifications
Manufactured: Fab 30 in Dresden, Germany
Process Technology: 0.18 micron copper process technology
Cache Size: L1 - 128KB
L2 - 256KB
Voltage: 1.75v
Die Size: 128mm2
Number of Transistors: 37.5 million
Infrastructure: Socket A
QuantiSpeed" Architecture for enhanced performance
Nine-issue superpipelined, superscalar x86 processor microarchitecture designed for high performance
Multiple parallel x86 instruction decoders
Three out-of-order, superscalar, fully pipelined floating point execution units, which execute x87 (floating point), MMX" and 3DNow!" instructions
Three out-of-order, superscalar, pipelined integer units
Three out-of-order, superscalar, pipelined address calculation units
72-entry instruction control unit
Advanced hardware data prefetch
Exclusive and speculative Translation Look-aside Buffers
Advanced dynamic branch prediction
3DNow!" Professional technology for leading-edge 3D operation
21 original 3DNow!" instructionsthe first technology enabling superscalar SIMD
19 additional instructions to enable improved integer math calculations for speech or video encoding and improved data movement for Internet plug-ins and other streaming applications
5 DSP instructions to improve soft modem, soft ADSL, Dolby Digital surround sound, and MP3 applications
52 SSE instructions with SIMD integer and floating point additions offer excellent compatibility with Intels SSE technology
Compatible with Windows® XP, Windows 98, Windows 95, and Windows NT® 4.x operating systems
266MHz AMD Athlon" XP processor system bus
Source synchronous clocking (clock forwarding) technology
Support for 8-bit ECC for data bus integrity
Peak data rate of 2.1GB/s
Multiprocessing support
Support for 24 outstanding transactions per processor
The AMD Athlon" XP processor with performance-enhancing cache memory features 64K instruction and 64K data cache for a total of 128K L1 cache. 256K of integrated, on-chip L2 cache for a total of 384K full-speed, on-chip cache.
Socket A infrastructure designs are based on high-performance platforms and are supported by a full line of optimized infrastructure solutions (chipsets, motherboards, BIOS).
Available in Pin Grid Array (PGA) for mounting in a socketed infrastructure
Electrical interface compatible with 266MHz AMD Athlon XP system buses, based on Alpha EV6" bus protocol
*whew*, now that the manufacturer specifications are out of the way, let's take a closer look at the key features...
The Athlon XP and PR
 
Code named"Palomino", the name was changed to the Athlon XP upon release. The definition of "XP" is eXtreme Performance. Say what you want about the name, but there isn't much doubt that an extreme performer, it is. It also happens to be a coincidence that Microsoft released their current desktop operating system, also called XP, around the same time.
Perhaps the most controversial aspect of the XP is the return of the performance rating. Collaborating with Cyrix about 5 years ago, the two manufacturers lagged a little behind Intel in clock frequencies. The consumer back then, and this thinking hasn't really changed much today, would likely conclude that a higher clocked processor is faster, regardless of manufacturer. This "PR" system was introduced to make their own processors appear to be similar to Intel in terms of performance. Eventually, this scheme failed, as it wasn't really true. Learning their lesson, AMD dropped the PR system, and Cyrix eventually sold its assets to VIA. Why bring it back? Well, AMD made sure that it's processors were performing as their PR rating suggests. Before we continue, here's a rundown of their current PR system, and actual clock speed...
AthlonXP 2000+ = 1.67GHz
AthlonXP 1900+ = 1.60GHz
AthlonXP 1800+ = 1.53GHz
AthlonXP 1700+ = 1.47GHz
AthlonXP 1600+ = 1.4GHz
AthlonXP 1500+ = 1.33GHz
According to AMD, there are two factors in determining CPU performance, and that is the instructions per clock cycle (IPC) and clock speed... "Until recently, the IPC of most computer processors was identical, so clock speed alone was used to determine performance capability. In current processors, however, IPC is different for competing processors, so performance is defined using both IPC and frequency. The end result is that frequency alone no longer determines performance. As a result of its QuantiSpeed architecture, the AMD Athlon XP processor has an optimum balance of IPC and frequency to achieve high levels of real world PC application performance."
Now, unlike the past, where the PR was a rating compared to an Intel CPU, this is not the case now. It's a common misconception, but the PR rating does not compare an Athlon XP against a Pentium 4, but against a Thunderbird. Therefore, a 1.53GHz XP performs like an 1.8GHz Thunderbird. How did they come up with these numbers? Testing, and a lot of it. All the information is available on , and if you want to learn more about it, their on procedures and results are explained there.
Looks like a Thunderbird to me...
Actually, it's pin compatible with the Thunderbird motherboards, but of course, there's no guarantee that your motherboard will support it. Taking a closer look, there are actually quite a few physical differences with the Thunderbird...
To begin with, the CPU is now designed using the Organic Pin Grid Array. Unlike Thunderbirds, which were made of ceramic, the OPGA will allow for cheaper production costs, and by not being as electrically restrictive, this should allow for further scalability than before.
The capacitors which used to surround the core of the Thunderbird have now been moved to the bottom. I'm not sure of the reasons to be honest, but my guess is that it's more efficient. Bah! Who really knows? The likely reason is that the core of the XP is larger than the Thunderbird. Speaking of which, the core is still rectangular, but is now rectangular up to down, rather than left to right.
With the reshaped core, and OPGA packaging, the CPU is a little thinner than the Thunderbird. This may pose a problem with some heatsinks, whose clips have been specifically designed for Thunderbird weight specifications. It's best to peruse AMD's recommended heatsink list to make sure yours is compliant.
Another thing you'll notice is the L1 traces have been cut. It differs a bit from earlier Athlons, as this time, it isn't really easy to use the pencil trick on it. For those unfamiliar with this, by joining the LI traces, you can unlock your multiplier. Because the higher clocked Athlon XPs have such a high multiplier, overclocking via the FSB only makes stable overclocks harder than before. The reason the pencil trick isn't as easy anymore is not only is the L1 traces cut, but there are now small pits in between. These pits need to be filled in before joining the traces with conductive material. There are several guides available online demonstrating this, and sells a DIY unlocking kit for Athlon XPs.
The Athlon Technology
Other than the usual 200/266 FSB support, as well as DDR support, there is a lot going on in the Athlon XP, compared to the Thunderbird. I already listed the specifications at the beginning of the review, but the most notable features about the Athlon XP is the introduction of QuantiSpeed Architecture, and 3DNow! Professional.
QuantiSpeed Architecture
The key features of QuantiSpeed are as follows:
Nine-issue superpipelined, superscalar x86 processor microarchitecture
Multiple parallel x86 instruction decoders
Three out-of-order, superscalar, fully pipelined floating point execution units
Three out-of-order, superscalar, pipelined integer units
Three out-of-order, superscalar, pipelined address calculation units
72-entry instruction control unit
Advanced hardware data prefetch
Exclusive and speculative Translation Look-aside Buffers
Advanced dynamic branch prediction
Basically, QuantiSpeed will allow for more operations per clock cycle. Its floating point unit is a lot beefier than the Thunderbird, and at the same clock speeds, the QuantiSpeed will be able to handle more instructions faster.
One of QuantiSpeed's key features is the advanced hardware prefetch. What this does is that it allows the CPU to anticipate, or guess, what will be done next and move that information to the cache for faster access. Say if you're working on a word document. The processor follows you as you work, and predicts what you're going to do next. Say that you plan to check for spelling. If the processor guesses correctly, your spell check will open a lot faster. Of course, if it guesses wrong, the cached data is discarded. Thanks to the shorter pipeline, this isn't as noticeable as it would be for the longer pipelined Pentium 4.
3DNow! Professional technology
21 original 3DNow!" instructions
19 additional instructions to enable improved integer calculations
5 DSP instructions
52 SSE instructions
Think of it as 3DNow! on steroids. Outside of the original instructions, 3DNow! Pro introduces 19 new integer instructions for accelerating speech and audio encoding, as well as improving your 'net experience. Intel promises similar things with it's Netburst architecture.
5 Digital Sound Processor instructions are added, which should improve the experiences of the user with any communications software, such as modems, as well as sound applications.
In my opinion, the best part though is the added support for Intel SSE. Now the Athlon can gain extra performance in applications that natively support SSE, but not 3DNow!, which can only be a good thing.
One thing not mentioned yet is power consumption. According to documentation, the Athlon XP uses up to 20% less power than before. The core voltage is the same, but the amount of power needed has been optimized. Another key feature is the introduction of the internal thermal diode (yay!), which will give more accurate temperature readings, as well as provide greater security to overheating. This will be accomplished by throttling the clock speed, or shutting down when a temperature danger zone is reached. Unfortunently, there aren't a whole lot of motherboards that make use of this feature, and it's still not safe to run an Athlon without a heatsink. Why would anyone want to do that? Same reasons some people think kicking a PC will make it work, hence the term "percussive maintenance".
Performance
With all these whiz-bang features, just how fast is the Athlon XP? Plenty fast. It runs cool also. Before we get to benchmarking, I should mention that I tried the multiplier unlocking trick, but admittingly, my resources were limited. I wasn't able to unlock the processor, and was forced to overclock via the FSB. The average overclock I have been able to establish is 11.5x144, give or take 1MHz. If you read my Abit KG7-RAID or MSI K7N420 Pro reviews, I explain a little more there.
For testing, we're going to compare performance with an overclocked Thunderbird, which is officially rated at 1.4GHz, but which I boosted to 1.53GHz to match the Athlon XP 1800+. The test bed is as follows:
Athlon XP 1800+ (stock speed), 512MB (2 Dimms), Abit KG7-RAID, MSI StarForce GeForce 3, Windows 2000 Professional, Detonator 23.11, VIA 4 in 1 v4.35a
Athlon TBird 1.53 (11.5x133), 512MB (2 Dimms), Abit KG7-RAID, MSI StarForce GeForce 3, Windows 2000 Professional, Detonator 23.11, VIA 4 in 1 v4.35a
Benchmarks
 
Thunderbird 1.53 (left), and Athlon XP 1.53 (right)
 
Thunderbird 1.53 (left), and Athlon XP 1.53 (right)
For those of you still "stuck" with older Thunderbirds, my advice to you is to hold on to those babies, especially if you've gotten lucky with an AXIA core, or any overclockable core. Although the Athlon XP outscores the Thunderbird, it isn't a total blowout. That is, until we overclock it...
Athlon XP 1.53 (left), and Athlon XP 1.66 (right)
You can check our motherboard reviews for the gaming benchmarks, but I grabbed a couple of quick screenshots of the 3D Mark 2001 scores for you...
 
640x480 (left), and 1024x768 (right)
I wanted to add one more number here..., heat.
Using our beloved Swiftech MCX462, we maintained full load temps at about 38C. For the record, at the same clock speed, the Athlon Thunderbird hovered in the 44C to 45C range.
Final Words
Well, I think the benchmarks speak for themselves. AMD designed one heck of a chip. The Athlon XP, regardless of clock speed, easily outperforms the Thunderbird CPU. With the design changes, AMD should be able to keep up with Intel, and at the same time, leaving them with some headroom to grow. The performance rating is not my favorite thing, but I actually don't see this as a big issue.
There are a few things one should take note of. The CPU core is still extremely prone to cracking when improperly installing a heatsink. Some common sense, and it helps to have a well designed heatsink clip, will prevent this from happening. There is also no lack of XP support from manufacturers, but there doesn't seem to be much support for the thermal diode, which is a shame. For those of you with older motherboards, keep in mind that there is no guarantee that the XP will work. If you're lucky, a BIOS upgrade solves that problem, but don't be surprised if it doesn't work. Owners of most DDR motherboards should be ok. Finally, AMD has successfully prevented casual overclockers from even bothering to try their hand at unlocking. The hardcore guys will certainly continue to defy the man, but with the "cut and dug" bridges, it has gotten a lot tougher.
Other than the speed improvements, a lot will be happy to know that AMD's pricing strategy hasn't changed much, and they continue to have a more appealing price/performance ratio. For those of you with quality parts in your current AMD Thunderbird/Duron systems, there isn't much to do if you want to upgrade. Power requirements are equal, DDR support is there, and most heatsinks should work fine. It always helps to double check their site.
With the introduction of the Northwood, AMD better make sure they can keep pace. I have a feeling that Intel is going to start ramping up the clock speed, and the PR rating isn't going to look like much when the're stuck at 2500+ and Intel has 3.5GHz P4s running around. Out of the current crop of Athlon XPs, I think the 1800+ is the best buy, and it will look mighty fine powering your rig.
AMD:
90%
Pros: Great performance, decent overclocking potential, runs relatively cool, good pricing.
Cons: Lack of support for internal thermal diode, fragile construction, overclocking is harder than before.
Agree? Disagree? Discuss it in our forums.
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