As you surely remember from our previous Athlon XP 2200+ Review, these processors couldn't boast very good overclocking potential. Our Athlon XP 2200+ working at 1.8GHz actual core frequency and using 133MHz FSB allowed increasing the bus frequency only up to 142MHz. This way the maximum core working frequency we managed to achieve then made only 1917MHz. In other words, Athlon XP 2200+ allowed only 6.8% frequency increase over the nominal, which is definitely not enough to reach the speed of Athlon XP 2400+. Nevertheless, as we see, AMD didn't have any difficulty announcing a new Athlon XP 2400+, as well as Athlon XP 2600+, which core frequency is much higher. How on earth did the engineers manage it?
The answer is very simple: to find it just take a closer look at the results shown by wcpuid utility, which displays the info about the CPU in the system. The screenshot below was taken from the older (here we mean not outdated, but the previous) Athlon XP 2200+:
And this is a screenshot I took on a system with a new Athlon XP 2600+:
So, the first thing I would like to draw your attention to is the fact that new Athlon XP have a new core stepping. If the first Athlon XP based on Thoroughbred core had 0 core stepping, then the new processors feature core stepping equal to "1". Of course, the processors of the new core stepping are designed to allow new Athlon XP CPUs to work normally at higher core frequencies.
It's true, in this case it is all about Thoroughbred core redesign, which allowed AMD to increase Athlon XP core clock frequencies much more. When the company shifted from Thunderbird to Palomino core, they have already done something like that, however, this was not the only measure undertaken, as they also introduced a few changes to the processor fie architecture. Now the architecture remained unchanged. AMD has simply optimized its Thoroughbred.
Speaking more precisely I would like to point out that the mentioned above redesign added a new metallic layer to the processor die reducing the spurious capacitance. Moreover, the core structure got special decoupling capacitors responsible for combating electromagnetic interference. Also some changes were made to the positioning of the components on the die surface. As a result, AMD managed to retain the same architecture, and at the same time make it possible to increase the core clock frequency as well as reduce the heat dissipation of Athlon XP on Thoroughbred core quite tangibly.
The next table allows you to compare the features of the new and the old core:
Athlon XP 2200+
Thoroughbred, stepping 0 Athlon XP 2600+
Thoroughbred, stepping 1
Core frequency 1800MHz 2133MHz
Bus frequency 266MHz (133MHz DDR)
Technology 0.13micron
Cache size L1=128KB, L2=256KB (384KB total)
Nominal Vcore 1.65V 1.65V
Die size 80sq.mm 84sq.mm
Number of transistors 37.2 million 37.6 million
Socket Socket A
Max. core temperature 85oC 85oC
Max. heat dissipation 67.9W 68.3W
Typical heat dissipation 61.7W 62.0W
As you can see, the new core is slightly bigger. However, if the core frequency grows up a lot, the heat dissipation increases just a tiny bit, which is very important. This way the redesign proved highly efficient, no doubt.
Another change introduced in the Athlon XP family together with the launching of the new Athlon XP 2400+ and 2600+ is made to the formula used to calculate the processor performance rating. In fact, there is nothing to be surprised at. Athlon XP processors get their rating basing on their performance in some reference benchmarks (the list of these benchmarks is available on AMD's site). Of course, as the frequency grows up the performance gain cannot remain constant. Since the CPU is not working with other system components any faster, because the processor bus frequency remains the same, the performance gain provided by the same repeating increases in the core frequency gets smaller and smaller. That is why on making new Athlon XP processors AMD discovered that 66MHz frequency growth is not enough to increase the CPU rating by 100. That is why the old formulas showing the dependence of the rating on the frequency do not work any more. To make things clear to you I would like to suggest looking at the table below, which illustrates the dependence of the performance raying of the contemporary Athlon XP processors and their core clock frequency:
CPU Frequency, MHz
Athlon XP 1500+ 1333
Athlon XP 1600+ 1400
Athlon XP 1700+ 1460
Athlon XP 1800+ 1533
Athlon XP 1900+ 1600
Athlon XP 2000+ 1667
Athlon XP 2100+ 1733
Athlon XP 2200+ 1800
Athlon XP 2400+ 2000
Athlon XP 2600+ 2133
It's true that if the frequency had been calculated with the older formula, then Athlon XP 2400+ worked at 1933MHz, for instance. However, its actual frequency appeared higher. As for Athlon XP 2600+, its frequency could make only 2.067MHz if calculated with the old formula. In reality the working frequency for this processor is 2133MHz. Well, a really pleasing trifle I should say :)
Rating Frequency, MHz Thoroughbred core, stepping 0 Thoroughbred core, stepping 1
Vcore Max. heat dissipation Typical heat dissipation Vcore Max. heat dissipation Typical heat dissipation
1700+ 1467 1.5V 49.4W 44.9W - - -
1800+ 1533 1.5V 51W 46.3W - - -
1900+ 1600 1.5V 52.5W 47.74W - - -
2000+ 1667 1.6V
1.65V 60.3W 54.7W 1.6V 61.3W 55.7W
2100+ 1733 1.6V 62.1W 56.4W - - -
2200+ 1800 1.65V 67.9W 61.7W 1.6V 62.8W 57W
2400+ 2000 - - - 1.6V
1.65V 65.3W
68.3W 59.3W
62W
2600+ 2133 - - - 1.65V 68.3W 62W
New Thoroughbred core will be used not only in Athlon XP 2400+ and 2600+, but also in the previously launched Athlon XP 2200+ and 2000+. Unfortunately, there are no evident differences in the marking between the CPUs based on the older and the newer core, even despite pretty noticeably differences in terms of overclocking and heat dissipation. However, you still can easily distinguish between the CPUs on the old Thoroughbred core and a new one with the help of a few additional tricks. The table below contains electrical and thermal specs for the existing Athlon XP CPUs based on different steppings of the Thoroughbred core:
As you can see, there will be only two models based on different cores: Athlon XP 2200+ and 2000+. Moreover, most Athlon XP 2000+ and 2200+ processors built on the new core stepping will boast lower nominal voltage (Vcore=1.6V). These CPUs should be your choice once you decided you might be willing to do some overclocking one day. The nominal Vcore can be easily read from the CPU marking:
In conclusion to our story about the peculiarities of the new Thoroughbred core with 1 stepping, I would like to stress one more fact. New Athlon XP 2400+ and 2600+ support 15x and 16x clock frequency multipliers respectively. Unfortunately, now not all mainboards know to recognize this clock multiplier correctly, so I suggest checking if your mainboard can work with a processor like that or not, before buying yourself a new CPU. As for us, we ran the tests of the new Athlon XP processor on EPoX EP-8K3A+, which proved excellent. So, this is the first mainboard that for sure works fine with the newcomers.
