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Well, processor overclocking has become very popular lately. Many users, who are willing to get a high-performance system without investing much money, prefer those processors, which can be easily overclocked. The one to unwillingly stimulate this process and turn it into a massive trend appeared Intel, when they launched their Celeron 300A CPUs. The processors from this family broke all possible and impossible overclocking records. They allowed increasing the frequency by 1.5 times and offered the performance not at all worse than that of Pentium II 450MHz solutions, which were in those times the fastest desktop processors available. It was exactly then that they started regarding overclocking as a great means of increasing performance. The mainboard manufacturers began to pay more attention to overclocking friendly functions of their products, and the entire computer community was watching all the CPUs carefully trying to find good pieces for overclocking needs.

If we try to analyze the history of well-overclockable processors, we will be able to single out certain tendencies. Usually good overclockability is typical of those processors based on the same core, which work at lower nominal clock frequency. This statement has a very logical explanation. The CPUs based on the same core feature almost the same frequency potential. As a result, the slower models have more room for frequency increase than their initially faster counterparts.

It is evident that the 0.13micron processors boast the highest overclocking potential today. Both leading CPU manufacturers, namely, Intel and AMD, have already learnt to use this technology and are now offering the whole families based on 0.13micron cores. In this article we will devote special attention to overclocking of the solutions manufactured this way. So far, there are three processor families based on 013micron cores: AMD Athlon XP, Intel Celeron and Intel Pentium 4. No wonder that each family has its best overclockable model. So, today we will take a look at all three solutions to find out which processors suit better for overclocking needs, what results can be achieved and which product will be the best choice from the price-to-performance point of view.

So, as I have already said, we will meet three CPUs, which have already deserved their legendary reputation among overclocking fans. They are:

  • AMD Athlon XP 1700+ based on Thoroughbred core;
  • Intel Celeron 2GHz based on Northwood-128 core;
  • Intel Pentium 4 1.8A GHz based on Northwood core.

Note that it doesn't make much sense to take the fastest models of the family for overclocking experiments. Their end frequency after overclocking will be no higher, because the limitations are all applied to the processor core. Besides, the faster models of the family differ from the slower ones based on the same core only by the clock frequency multiplier. Anyway, let's take a closer look at our testing participants.

AMD Athlon XP 1700+

Well, AMD Athlon XP processors haven't pleased us with any high overclocking potential lately. However, the situation changed for the better after they had moved Fab30, where AMD processors are produced, to 0.13micron manufacturing technology. It looked as if AMD decided to force the upgrade of the manufacturing equipment there, because even the slowest processor models are now based on the new 0.13micron Thoroughbred core. The CPU with the lowest nominal core frequency from AMD today is Athlon XP 1700+. The slower models have been discontinued, and if they are still shipping to the market, it is only because of very big remaining stock. However, you shouldn't forget that the same Thoroughbred core is now used in the fastest Athlon XP processors. Therefore, it would be logical to expect Athlon XP 1700+ to show really good overclockability.

But, nevertheless, Athlon XP 1700+ cannot reach the frequency of processor models rated as 2700+ and 2800+. The matter is that Thoroughbred core can be of two steppings: the slow "A" stepping and the fast "B" stepping. The core of the new "B" stepping features additional metal layers and additional capacitors reducing the EMI, which allows it to work at higher clock frequencies. The Athlon XP 1700+ processors selling in the today's market are based on the slower A core, which is also used in CPUs rated up to 2200+. This way it would be quite logical to suppose that the currently available Athlon XP 1700+ could be successfully overclocked up to the level of Athlon XP 2200+.

At the same time, AMD has already told us that very soon they would move all their Athlon XP processors to Thoroughbred cores of faster B revision. It means that we may see even mode overclockable Athlon XP 1700+ CPUs capable of working at the frequencies of Athlon XP 2800+. However, I have no idea when this is to happen.

When you will look for an Athlon XP 1700+ with intention to overclock it later on, you should keep in mind that there are still some older processors based on the 0.18micron Palomino core. That is why you have to make sure beforehand that the CPU you are getting is based on the new Thoroughbred. In fact, the exteriors of Palomino and Thoroughbred do differ quite a lot from each other: Palomino die is much bigger and is shaped as a square, while the Thoroughbred core is rectangular.

And now the most important thing. Athlon XP 1700+ based on Thoroughbred core costs less than $60, which may make this processor one of the most popular overclocking choices for those who prefer better value solutions (if the performance proves appropriate, of course).

Well, let's now turn from our scholastic discussions (in the positive meaning of this word) to actual practice. For our investigation we got an Athlon XP 1700+ based on Thoroughbred rev. A core.

The actual clock frequency of this processor makes 1466MHz. the nominal Vcore equals 1.5V.

Our CPU was marked as:


If we read this marking, we will understand that the CPU was manufactured in November 2002, i.e. it is quite "fresh". At the same time I would like to say that Athlon XP 1700+ processors based on Thoroughbred core differ from their Palomino based fellows by their marking as well. The 0.13micron core is indicated in the marking by the first 4 "AXDA" letters.

Bearing in mind that the maximum clock frequency of revision A Athlon XP CPUs on Thoroughbred core is 1800MHz (this is the clock frequency of Athlon XP 2200+), the top frequency for Athlon XP 1700+ after we overclock it will lie somewhere close to this value. And our predictions came true. We managed to overclock our Athlon XP 1700+ CPU up to slightly above 1.9GHz. This is exactly the average overclocking potential of Thoroughbred based Athlon XP 1700+ processors.

However, we would like to point out one peculiarity of the new Athlon XP 1700+. Namely, many of these processors available in the today's market do not have a locked clock frequency multiplier. In other words, any overclocker will be able not only to change the FSB frequency, but also to adjust the CPU clock frequency multiplier without any additional effort on his part, i.e. simply by using the overclocking friendly feature of his mainboard. Keeping this in mind, and also knowing that the increase in the FSB frequency also provides a certain performance improvement, we reduced the multiplier to 9.5 and raised the FSB frequency up to 200MHz. in this mode our CPU worked at 1900MHz. To ensure stable functioning we raised CPU Vcore from the nominal 1.5V up to 1.65V. In this mode the system stability appeared just excellent and we managed to run the whole set of tests without any problems.

As we see, the mainboard recognized this CPU as Athlon XP 2400+. Well, I agree with this completely. The performance of our Athlon XP 1.9GHz was just about the same level.

Speaking about the testbed, we have to mention that we overclocked our processor with EPoX EP-8K3A+ mainboard, which proved impressively stable with 200MHz FSB. Although it is based not on the newest VIA KT333 chipset, the use of this particular mainboard was absolutely justified. VIA KT333 performed not worse than VIA KT400, but boasted higher stability. It definitely can be explained by a better polished BIOS and simpler PCB layout. As for the memory, its frequency equaled 200MHz with 200MHz FSB that is why we used DDR400 modules from Corsair (XMS3200). The CPU cooling was quite common: CoolerMaster CP5-6J31C with a copper footing pad.

Intel Celeron 2.0GHz

The overclocking story of Celeron processors is completely different. Any of the processor cores ever used in the CPUs of this family had its overclocking records. It is mostly because Intel Celeron were always based on the same cores as the faster processor families, with that only difference that the L2 cache was twice as small, bus frequency was reduced and the clock frequencies were lower. As for the cache, there is no way to get its cut-down half back, however, in terms of frequencies, overclocking comes to rescue and allows speeding up the low-cost processors immensely. Not so long ago, following in the footsteps of Pentium 4, Celeron processor family acquired a 0.13micron Northwood core. The first Celeron CPUs based on it appeared Celeron 2.0GHz. As we have expected, they appeared very easy to overclock. Their core frequency can be raised up to that of the fastest Pentium 4 models, which is roughly 3GHz. And only the cut down 128KB L2 cache, prevents Celeron from beating all overclocking records.

All 0.13micron Celeron processors on Northwood-128 core available in the today's market feature B1 core revision. This is a "lite" analogue of Northwood B0 core used in Pentium 4 processors up to 2.53GHz core clock. However, bearing in mind the fact that Celeron features fewer transistors than Pentium 4 because of the smaller L2 cache reduced from 512KB to 128KB, the peak frequencies for Celeron processors lie far beyond the notorious 2.53GHz bar. Celeron 2.0GHz, which promises to be quite a good option for overclockers, costs around $90. It is not as inexpensive as in case of Athlon XP 1700+. However, you can achieve much higher frequencies here.

For our experiment we took the regular Celeron 2.0GHz CPU:

As we see, the CPU really does feature 128KB L2 cache and is designed to work with 400MHz bus. Keeping in mind that the clock frequency multiplier of all Intel processors is deadly locked, this bus frequency gives us a lot of room for increasing the FSB frequency. The nominal Vcore by this CPU equals 1.525V.

As you can notice from the picture above, S-Spec of our processor is SL6LC. This particular S-Spec is typical of all Celeron 2.0GHz processors, if we take the info on Intel's site for granted. However, you still can come across some Intel Celeron 2.0GHz CPUs with SL6HY S-Spec. Unfortunately, as the practical reports show, these CPUs get overclocked a bit worse than their counterparts. Therefore, if you are selecting a Celeron 2.0GHz for overclocking needs, we would recommend the one with SL6LC S-Spec.

Practice proved that many Celeron processors based on Northwood-128 core, especially those with SL6LC S-Spec, can easily overclock up to about 3GHz. Our investigation added more evidence to that. When we overclocked our CPU, we managed to raise the FSB frequency up to 150MHz, which did provide the clock rate of exactly 3GHz with the locked 20x frequency multiplier. To ensure appropriate stability, the Vcore was set to 1.65V, although we have to admit that the increase in Vcore doesn't tell on the overclockability of these processors that much. Unfortunately, further overclocking led to system instability. However, the 1.5-time frequency increase and nevertheless smooth functioning of the system can hardly be called a poor result.

To overclock our Celeron 2.0GHz processor we used MSI 845PE Max2 mainboard based on i845PE chipset. The AGP/PCI bus frequencies were locked at 66MHz/33MHz respectively, and to clock the memory bus we used 5:4 divider. As a result, we managed to overclock the memory bus up to 187MHz by increasing the FSB frequency up to 150MHz. Therefore, we can say that we used DDR375 SDRAM in our testbed. As for the memory modules, they were the same as those we used for Athlon XP 1700+ overclocking: Corsair XMS3200. We used no special cooling in our system, and the CPU was equipped with a standard boxed cooler.

Intel Pentium 4 1.8A GHz

When Intel launched its first Pentium 4 processors based on 0.13micron Northwood core, their clock frequencies started from 2GHz. However, a bit later they introduced processor models based on the same core but working at 1.6GHz and 1.8GHz. Of course, these processors were the ones to please the public with their overclocking potential. At first, Pentium 4 Northwood 1.6GHz appeared the most popular overclocker's solution. However, they have almost disappeared completely from the market by now. So, we have every right to regard Pentium 4 Northwood 1.8A GHz as the today's eldest Pentium 4 processor (by the way, the "A" letter indicates that this CPU is built on 0.13micron core with 512KB L2 cache). Of course, we will perform our overclocking experiments with this particular CPU.

0.13micron Pentium 4 1.8A GHz processors are now available in two versions differing by the core stepping: the earlier stepping - B0, and the later stepping - C1. Nevertheless, almost all the currently selling CPUs are built on B0 core stepping. The C1 core stepping has just appeared, and is still quite hard to find. But even the B0 core is very well overclockable. The B0 Northwood core is used in Pentium 4 processors with up to 2.53GHz core frequency. This gives us to understand that B0 cores still have quite sufficient potential. Speaking about C1 stepping, we should say that these cores are used for Pentium 4 processors with up to 3.06GHz core frequencies. Moreover, they feature slightly smaller die size and are manufactured with 300mm wafers. However, all these things do not give us the right to state that Pentium 4 1.8A GHz based on C1 core stepping will overclock better than the same CPU based on B0 core stepping. It looks as if Intel were sorting out dies specifically for work at higher clock rates that is why it might be a really hard task to fins a low-frequency processor, which could get overclocked over 3GHz. Unfortunately, the statistics available today doesn't allow us to find that particular criterion, which could help us distinguish between the well-overclockable and the poorly-overclockable processors.

At the same time, almost every Pentium 4 1.8A GHz with the core of any stepping can be overclocked over 2.4GHz-2.5GHz. That is why you can simply get any Pentium 4 1.8A GHz for your overclocking needs. Nevertheless, it is quite easy to tell a B0 stepping processor from a C1 one with the help of S-Spec. The CPUs with the older B0 cores have the following S-Spec: SL68Q, SL66Q, SL63X, SL62R or SL62P, and the CPUs with C1 stepping -SL6S6 or SL6LA.

In fact, we are quite uncertain that there could appear better overclockable Pentium 4 1.8A GHz CPUs. Yes, C1 core revision will get more and more widely spread with the time, however, for the reasons mentioned above their overclocking future is still pretty vague.

As for the price, Pentium 4 1.8A GHz cost around $150, which makes them the most expensive solution out of the three considered here. However, it doesn't mean that Pentium 4 1.8A GHz is not a smart choice for an overclocker, which we will see later in this article.

So, for our investigation we got a Pentium 4 1.8A GHz processor based on the older B0 core revision proved by the CPUID F24h (the CPUs with C1 core feature CPUID F27h):

This processor works at the 100MHz FSB and feature a locked 18x clock frequency multiplier. The nominal Vcore equals 1.5V.

S-Spec of our processor was SL68Q. By the way, these CPUs are available only in Boxes and can never be received in an OEM version.

Having overclocked this processor we were pleasantly surprised. The CPU got suddenly capable of working at the frequencies lying far beyond 2.5GHz. As a result, we managed to increase the FSB frequency up to 160MHz with the locked 18x multiplier, which lead to the end frequency of 2.88GHz. So, our Pentium 4 1.8A GHz showed the best overclocking potential of all the processors reviewed here. As we saw, the clock frequency of this processor can be increased by the good 60%!

To improve the system stability during the work at non-nominal frequencies, we increased the Vcore up to 1.65V.

The testbed where we benchmarked the overclocked Pentium 4 1.8A GHz, was configured the same way as for Celeron 2.0GHz. We used MSI 845PE Max2 mainboard based on i845PE chipset. The AGP/PCI bus frequencies were locked at 66MHz/33MHz respectively, and to clock the memory bus we used 5:4 divider. As a result, the memory worked at 200MHz (400MHz DDR). Therefore, Corsair XMS3200DDR400 memory modules were just the right thing for us to use in this system. We used no special cooling in our system, and the CPU was equipped with a standard boxed cooler.

The table below sums up all the features of the CPUs tested:

Athlon XP 1700+
Pentium 4 1.8A
Celeron 2.0
Frequency 1466MHz 1800MHz 2000MHz
Bus frequency 266MHz
(133MHz DDR)
(100MHz QPB)
(100MHz QPB)
Manufacturing technology 0.13micron 0.13micron 0.13micron
Cache size 128KB L1
256KB L2
8+12KB L1
512KB L2
8+12KB L1
512KB L2
Nominal Vcore 1.5V 1.5V 1.525V
Die size ?
Transistors 37.2 million 55 million ?
Infrastructure Socket A Socket478 Socket478
Max. core temperature 90oC 68oC 68oC
Max. heat dissipation 49.4W 55.5W 70.4W
Typical heat dissipation 44.9W 41.6W 52.8W
Frequency overclocking 1900MHz 2880MHz 3000MHz
Frequency incrrase during overclocking 30% 60% 50%
Approximate pricing (01/01/2003) $60 $150 $90

Testing Methods

When we planned these tests, we aimed at determining, which CPU would be the best choice for an overclocker. Therefore, we decided to compare the performance of different processors after overclocking them. At the same time we have also included the results shown by the same CPUs working at their nominal frequencies.

We have already described the CPU frequencies and the testbeds configurations above that is why now we will just sum up everything in a brief list of hardware involved in this test session:

  • CPUs: AMD Athlon XP 1700+, Intel Pentium 4 1.A GHz, Intel Celeron 2.0GHz;
  • Mainboards: EPoX 8K3A+ (VIA KT333), MSI 845PE Max2 (i845PE);
  • Memory: 2 x 256MB Corsair XMS3200 (DDR400 CL2 SDRAM);
  • Graphics card: ATI RADEON 9700 Pro;
  • Hard disk drive: Seagate Barracuda ATA IV, 80GB.

The tests were run in Windows XP operation system. The memory timings were set to get the maximum performance.


First of all, we used the synthetic PCMark2002. This test serving to evaluate the system performance involves a lot of relatively simple algorithms.

The results show that all the three tested processors are equally fast in nominal mode. And after overclocking the victory belongs to the processor, which overclocks better. In our case it is Intel Pentium 4 1.8A GHz, which frequency got 60% higher. We would also like to draw your attention to the great results shown by Intel Celeron, which frequency rose up to 3GHz. The thing is that the algorithms used by PCMark2002 to measure the processor power do not involve big data packs, so that the small 128MB L2 cache appears quite enough for comfortable work. Unfortunately, this is a very rare thing in real applications, which we will see later on.

During the memory subsystem performance test carried out with the help of the same PCMark2002, the best results belonged to overclocked Pentium 4 and Celeron. This is absolutely not surprising: the bus bandwidth of these processors is much higher than that of Athlon XP.

However, the results obtained in SiSoft Sandra 2003 seem even more logical:

In nominal mode all the three processors show almost the same results, because the maximum theoretical bandwidth of the bus between the processor and the memory is about the same in all three systems. In an Athlon XP based system the data transfer rate from the processor to the memory is limited by the processor bus bandwidth. In systems built on Celeron and Pentium 4 the data transfer rate is limited by the DDR266 bandwidth.

After overclocking the picture turns completely different. The FSB frequency grew up to 200MHz in Athlon XP based system and the processor bus bandwidth increased up to 3.2GB/sec. However, the memory starts working at 400MHz in a Pentium 4 based system, and it manages to get the leadership here. The only explanation here is the fact that the processor bus bandwidth in the overclocked Pentium 4 system gets much higher and reaches 5.1GB/sec.

Well, now let's pass from the synthetic benchmarks to the real applications.

Business Winstone checks the average performance in the typical office applications, such as: Lotus Notes R5, Microsoft FrontPage 2002 SP-1, Microsoft PowerPoint 2002 SP-1, Microsoft Excel 2002 SP-1, Microsoft Access 2002 SP-1, Microsoft Word 2002 SP-1, Microsoft Project 2000, WinZip 8.0, Norton AntiVirus and Netscape 6.2.1. As we see, in the tasks of the kind, the Celeron processor suffers a lot from its small 128KB L2 cache. Even when overclocked up to 3GHz, this processor is slower than Pentium 4 1.8GHz equipped with a 512KB L2 cache. As for the leaders, the best result belongs to Pentium 4 overclocked up to 2.88GHz and Athlon XP working at 1.9GHz.

Content Creation Winstone measures the performance of platforms intended for digital content creation. This test package includes: Adobe Photoshop 7.0, Adobe Premiere 6.0, Macromedia Director 8.5.1, Macromedia Dreamweaver 4, Microsoft Windows Media Encoder, Netscape 6.2.3, LightWave 3D [7.5] and Sonic Foundry Sound Forge 6.0. NetBurst architecture shows its best in the tasks of the kind, so Celeron and Pentium 4 appear quite fast here. Pentium 4 overclocked to 2.88GHz is again ahead of the race, and Athlon XP working at 1.9GHz falls behind the 3GHz Celeron this time.

During the sound files encoding into .mp3 format the overclocked Pentium 4 1.8A GHz again turns faster than the rivals. Well, this is the most expensive CPU of all our testing participants. More low-cost Celeron 2GHz and Athlon XP 1700+ fall only 10% behind the leader after overclocking.

The results obtained during video compression into MPEG4 format appeared very curious (we measured the time, each of the testing participants required). Celeron 2GHz and Pentium 4 1.8A GHz showed nearly the same performance. It looks as if the cache size doesn't matter that much for the video processing tasks. As for the overclocked up to 1.9GHz Athlon XP, it falls about 5-10% behind the leaders.

In data compression tasks, the L2 cache size on the contrary, matters a lot. That is why Pentium 4 with 512KB L2 cache is beyond any competition in WinRAR. Also, Athlon XP 1.9GHz outperforms the 3GHz Celeron, which is not at all surprising, even despite the gigantic clock frequencies difference.

Now, we are going to measure the performance of our overclocked platforms in 3D games.

In 3DMark2001 SE the picture is pretty common. Pentium 4 2.88GHz is the fastest, the second prize belongs to Athlon XP 1.9GHz, and the last one comes Celeron 3GHz.

In Return to Castle Wolfenstein game the overclocked Celeron processor appears a complete failure. Because of the insufficient cache memory, this processor falls not only behind the overclocked Pentium 4 and Athlon XP, but even behind the Pentium 4 1.8A GHz and Athlon XP 1700+ working at their nominal frequencies.

Besides, Celeron 3GHz is far from being fast in Unreal Tournament 2003. In general, we have enough facts to state that Celeron processor doesn't suit for games, even when overclocked. And Athlon XP 1.9GHz is quite OK in this test: it is only 0.3fps slower than Pentium 4 working at 2.88GHz.

We have also tested the processors performance in Doom3 alpha-version, which popped up in the web not so long ago. As you can see, the results are hardly very much different from what we have already seen in other games.

In conclusion we would like to offer you three more tests, where we measured the final rendering speed in popular 3ds max5 and LightWave 3D 7.5 test sets.

We have already pointed out several times that the computing power of AMD Athlon XP processor is higher than by Pentium 4. The final rendering speed in 3ds max 5 is another proof of the point. Athlon XP 1.9GHz and Pentium 4 2.88GHz coped with the reference scene equally fast. However, Celeron 3GHz is not too far behind: not more than 20%.

In Lightwave the rendering speed depends a lot on the scene type. If the result is influenced by the available cache memory in one case, in another case the clock frequency may be of no. 1 importance.


First of all, we would like to point out that overclocking all processors reviewed here allows increasing there performance quite tangibly. Bearing in mind that the CPUs discussed can easily overclock by 30%-60%, the performance achieved during overclocking can move the systems built on these processors from the budget segment into high-performance one without any additional expenses.

As for the question we asked in the very beginning of the article, namely, which processor of the three is the best choice for an overclocker, it appears really hard to answer it once and for all. As almost all the tests showed, the best performance belongs to Pentium 4 1.8A GHz overclocked up to 2.88GHz. However, this processor costs $150 and appears the most expensive overclocker's choice.

The better value Celeron 2GHz processor allows increasing its clock frequency by 1.5 times, but even working at 3GHz core clock rate it failed to impress us with its performance. In fact, only in content creation applications this processor proved really fast. In 3D games Celeron 3GHz appeared an outsider, which can hardly please dedicated overclockers.

The most balanced solution from the price-to-performance point of view turned AMD Athlon XP 1700+. Although this processor doesn't overclock as good as Intel solutions, its 1.9GHz are more than enough for almost any sort of tasks. Moreover, the price of Athlon XP 1700+ is much lower than that of Intel Celeron 2GHz and Pentium 4 1.8A GHz, therefore, this CPU seems to become the most popular overclocker's choice in the nearest future.

However, you, guy, are the only one to make the final conclusion here. We did our best to provide you all info you might need to answer this question for yourselves. Anyway, you should always configure the system depending on the tasks you will you it for. 

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