by Ilya Gavrichenkov
06/20/2005 | 01:46 PM
It is now perfectly clear that Intel’s NetBurst architecture didn’t turn out to be as successful as intended. Although Intel’s engineers aimed at frequencies up to 10 gigahertz as they were designing the Pentium 4 processor series, the practical implementation of these plans proved to be impossible. They just couldn’t keep the processor’s heat dissipation acceptably low at such high clock rates. As a consequence, Intel officially dumped its NetBurst products with frequencies above 4GHz. It’s good for Intel that desktop processors then took a different way of development. Instead of intensively increasing the clock rate, the CPU manufacturers chose the extensive approach by increasing the number of computation cores. If things remained unchanged, the Pentium 4 would lose its competitiveness against the rival products, but even now the senior processor models from AMD beat Pentiums 4 in a majority of tests.
<%BANNER[article]%>Anyway, the suddenly exposed deficiencies of the NetBurst architecture, namely high heat dissipation and power consumption of processors based on it, don’t mean Intel has no good CPUs in its product range. Climbing ever higher operational frequencies, Intel didn’t abandon the development and production of processors of the previous, Pentium III architecture. Even though Pentium III processors had been withdrawn from the desktop market, another suitable niche was soon found for them. CPUs that are architecturally similar to the Pentium III came to mobile computers. A perfected tech process and additional improvements for less heat and more performance rejuvenated the Pentium III which was reborn as Pentium M.
Pentium M series processors have had a great appeal for PC enthusiasts since their arrival. Besides low heat dissipation these processors boast a very good performance thanks to which Pentium M-based notebooks have won universal recognition. Unfortunately, it was impossible to use this highly promising CPU in desktop computers until recently due to the lack of appropriate chipsets. Some time ago a few mainboard makers overcame Intel’s opposition and released several platforms that permitted to install a Pentium M in a desktop computer. These platforms were somewhat ill-targeted, however: based on the same chipsets for notebooks, they were not quite appropriate for desktops due to their limited functionality and performance. For example, take their single-channel memory controller – only the cheapest desktop computer systems of today offer single-channel memory access.
Fortunately, another opportunity for crossing the Pentium M series with desktop computers was found. Despite its close relation to the Pentium III, the Pentium M uses the Quad Pumped Bus, and the engineers from ASUS developed a special adapter that allows installing mobile CPUs of the Pentium M class into ordinary mainboards for Pentium 4 processors. We’re going to check this prodigious gadget in this review and see what performance the Pentium M can offer to you if used in a desktop PC. We will start with a short description of the Pentium M architecture.
So, what is the Pentium M processor? Intel isn’t very talkative about the architecture of this product. The official documentation describes its formal characteristics and names just a few of its distinguishing features: a mobile PC oriented architecture, a dedicated stack manager, micro-ops fusion technology and Enhanced Intel SpeedStep technology. This description doesn’t clarify anything about the internal structure of the Pentium M. So, Intel doesn’t seem to want to disclose detailed information on the Pentium M and must have some reasons for that. Why?
The thing is the Pentium M represents a slightly improved P6 architecture that had previously been employed in CPU models from the Pentium Pro to Pentium III. Thus, the Pentium M looks like a step backward against the widely advertised NetBurst architecture. Yet you stop to regard the Pentium M as such after examining its internal structure closely. Taken as a whole, the Pentium M is better than the Pentium 4 in more respects than one! And please do not forget that the P6 architecture is among the best architectures Intel has ever developed – just think how long this architecture has been on the market in its various incarnations. So why can’t the Pentium M – the next incarnation of the Pentium III – become successful like the others?
Let’s first see which improvements were added by Intel to the good old Pentium III to transform it into the much-promising Pentium M.
Pipeline and execution core: The Pentium M is based on the same RISC architecture as Pentium III series CPUs, and there’s little difference in the execution cores of these processors. For example, they each have five execution units in total. But in the execution pipelines of these two CPUs there are already certain differences. While the Pentium III had a 10-stage integer pipeline, the pipeline of the Pentium M is somewhat longer. Of course, we don’t mean the Pentium M has a pipeline comparable in length to the one of Pentium 4 CPUs, but Intel’s engineers actually pursued the same goals when adding extra stages to the Pentium M’s pipeline. As you probably know, making the pipeline longer helps to lift the operational frequency of the processor up but the processor’s heat dissipation and power consumption grow up proportionally to the pipeline’s length which is especially important with mobile CPUs. So, judging by the available empirical data, the pipeline of the Pentium M processor is 12-14 stages long, i.e. a little longer than the Pentium III’s pipeline. Besides pushing the frequency bar higher, the longer pipeline was necessary due to the implementation of micro-ops fusion technology in the Pentium M. We’ll talk about it shortly.
Besides higher heat dissipation and power consumption, a longer pipeline in a modern superscalar processor capable of out-of-order execution leads to other negative effects. First of all, it is the performance hit occurring when the pipeline is refilled after an incorrect branch prediction. In many cases the developers try to reduce this negative effect as they add more stages to the execution pipeline. So, we should next dwell upon the improvements in the branch prediction unit they implemented in the Pentium M.
Improved branch prediction and hardware data pre-fetch: The purpose of the branch prediction logic is to minimize situations when the processor has to flush its pipeline because it has begun to execute a wrong program branch. The branch prediction logic of the Pentium M has considerably improved since the Pentium III. In fact, the Pentium M predicts branches much like the Pentium 4 does.
The branch prediction unit of the Pentium M is similar to the same unit of Prescott-core processors. It has additional logic for identifying loops and for predicting indirect branches. That is, the Pentium M considerably differs from its ancestor and is even more advanced than pre-Prescott Pentium 4 models in terms of branch prediction. Of course, it was impossible for the Pentium M to go far from the classical statistical branch prediction based on the branch history table. But Intel’s engineers managed to increase the prediction accuracy of the Pentium M by 20% over the Pentium III by adding a few innovations.
The first innovation is the loop recognition logic. With the ordinary statistical approach, branch predictions for end-loop conditions are always wrong. Of course, it is possible to enlarge the buffers that store the information about branches, but this would bring about long latencies necessary for all this info to be analyzed. So, the Pentium M uses a slightly different approach: independent logic identifies loops in the code and gathers information about the number of iterations made in the given loop. This greatly improves the prediction accuracy for end-loop conditions.
The second improvement is the indirect branch prediction logic. An indirect branch is a branch the branching address of which is not known at the time of compilation but is determined by the status of a particular register during execution of the program. The standard statistical prediction with a branch history table and a branch address table yields rather poor results here: no more than 75% of right predictions. That’s why the developers added a new table into the Pentium M which stores information about branching addresses of this type.
As the result of these two improvements, the execution units remain idle less often because of pipeline refills. Thanks to them, the performance of the Pentium M grew by about 7% above the performance of the Pentium III working at the same frequency.
Along with the improved branch prediction unit, the Pentium M features new logic for hardware data pre-fetch from memory to cache. The new algorithm employed in the Pentium M is more efficient than its analog from the Pentium III and is similar to the hardware data pre-fetch algorithm of Prescott-core Pentium 4 processors.
Micro-ops fusion: The Pentium M, like the Pentium III or Pentium 4, is a RISC processor. It means its execution units deal with internal, simplified commands rather than with complex x86 instructions. It is easier and faster to operate with RISC instructions than with x86 commands that often have three or more operands. As a result, x86 commands can be replaced with one, two or even three micro operations after they pass through the decoder. For example, the commands for storing data in memory or processing data in memory are decoded into two instructions each. In the first case, this pair consists of commands to calculate the address and to store the data in the buffer. In the second case, we have a command to read data from memory and a command that operates on these data. Considering that all modern processors are capable of out-of-order execution of micro operations, the commands that are part of a single x86 instruction may come to the execution pipeline independently. If one such micro operation can be executed aside of the other one, there’s no problem at all. But in the opposite case, if it is necessary to know the result of one instruction to execute another, the pipeline may come to a standstill. Such standstills aren’t actually dramatic for NetBurst processors where there are rather many execution units, but they may affect the performance of a CPU like the Pentium M very negatively. Moreover, such standstills involve the processor wasting power which is unacceptable for a mobile CPU. That’s why Pentium M processors have micro-ops fusion technology which is intended to prevent the execution units from staying idle.
The point of this technology is very simple. For a certain subset of x86 instructions (Intel doesn’t explicitly name them) the decoder binds together the micro operations that result from decoding a complex x86 command. It’s clear that the subset consists of x86 commands that split into independent micro-ops. Although micro-ops fusion technology reduced the number of instructions executed out of order by about 10%, the performance did not degenerate. On the contrary, this technology increases the performance of the processor by about 5% with integer data and by about 9% with floating-point data.
So, these micro-ops sequences are bound together by the fusion technology for execution in a particular order, and they are regarded as a single command until actually executed by the CPU. This approach helps to reduce the power consumption necessary to execute complex x86 instructions.
Dedicated stack manager: Another innovation implemented in Pentium M processors is the so-called stack manager which should reduce the load on the processor’s computation units when executing stack-related x86 instructions. The point of the Pentium M’s stack manager is in identifying instructions like PUSH, POP, CALL and RET that come to the processor’s decoder and in pre-processing them before they even arrive to the execution units. The dedicated stack manager works with the stack pointer register which is not changed in the Pentium M by the integer execution units like in processors of other architectures. Since software uses the stack quite actively, particularly when calling subprograms, the introduction of the dedicated stack manager reduces the load on the CPU’s execution units. This ultimately leads to higher performance and lower heat dissipation of the processor. Particularly, the dedicated stack manager reduces the number of instructions processed by the integer execution units by about 5%.
Processor bus: Although the Pentium M architecture is based on the Pentium III architecture, the Pentium M uses a completely different bus. The system bus in the P6 architecture had a peak bandwidth of 1GB/s which is too low by today’s standards. It was considered inappropriate to use this bus in modern processors, and Intel’s engineers decided to use the Quad Pumped Bus for the Pentium M. This is the bus employed in Pentium 4 family processors. In fact, the Quad Pumped Bus is the only point of similarity between the Pentium 4 and Pentium M. Indeed, even this bus is slightly different in the Pentium M, lacking some features. For example, the frequency of the system bus of the Pentium 4 processor has reached 800MHz by now, while the bus of the Pentium M operates at 533MHz today. Then, the Pentium M’s system bus only supports 32-bit addressing. That is, it can address no more than 4 gigabytes of memory. And lastly, the Pentium M’s bus doesn’t support multi-processor configurations. These differences are of little importance, however, and the Pentium 4 and Pentium M are compatible on the interface level. So, the processor for mobile computers can theoretically work with desktops-oriented chipsets.
SSE2 instructions: All Pentium M processors support SSE and SSE2 extensions. So, the number of supported SIMD instructions was extended in Intel’s mobile processors since the Pentium III. Yet, the Pentium M does not support the SSE3 set which first appeared in the Prescott-core Pentium 4.
Power-saving L2 cache: One of the remarkable things about the Pentium M is its very large L2 cache. The size of this cache is 2 megabytes. Using such large amounts of cache memory helps to unload the system bus and the memory bus which ultimately leads to lower power consumption of the CPU. We should also note that the Pentium M uses a special technique for reducing the power consumption of the cache. Like in other processors from Intel, the cache memory of the Pentium M has eight associativity sets. These sets are further divided into four quadrants in the Pentium M, each of which is accessed independently. As a result, Intel managed to considerably reduce the power consumption of the L2 cache (almost in four times). The downside of this solution is that the latency of the L2 cache has increased by 1 cycle if compared with the latency of the L2 cache of Pentium III processors.
As for the L1 cache, it is 64 kilobytes large (32 kilobytes for each code and data). This is two times the size of the Pentium III’s L1 cache. Another point of difference between the cache memories of the Pentium III and Pentium M is that the cache line of the latter is longer, 64 bytes. This change helps to work more efficiently with data structures of modern applications.
SpeedStep III technology: The Pentium M is intended for mobile computers, so it was equipped with additional power-saving technologies, SpeedStep III being the main one. According to available empirical data, the power consumption of processors depends linearly on the frequency and load of the CPU and quadratically on the CPU voltage. The developers have long been considering the idea of reducing the power consumption by reducing the frequency and voltage of the processor when it is not required to work at the full capacity. For example, the CPU load is far from 100% in a majority of office applications which are the most popular applications running on mobile computers. So, the frequency of the CPU can be reduced in such cases without compromising the user’s comfort. Besides the frequency, it is also possible to reduce the CPU voltage, and this is the point of SpeedStep technology.
The first implementation of SpeedStep in Pentium III-M processors offered two CPU modes: performance (or standard) and economical (with a lower frequency and voltage). The computer would enter the economical mode when the battery charge was below a certain level or when the CPU was idle. The second version of SpeedStep, implemented in mobile Pentium 4 models, added a third, adaptive mode. In this mode the switching between the max performance and reduced power consumption modes was performed dynamically, depending on the CPU load. That is, the CPU by default worked in the reduced-consumption mode, but could deliver the maximum performance as soon as a resource-consuming application was launched. The third version of SpeedStep technology, available in the Pentium M, features a more flexible adaptive mode. Pentium M processors have up to seven different states with reduced frequency and voltage each of which can be activated any time depending on the CPU load. Thus, SpeedStep III is a highly flexible technology that helps to reduce greatly the power consumption of the processor without any discomfort for the user.
CPU core: Pentium M models now available on the market are based on the
The table below compares the characteristics of the Pentium M on the
Pentium M | Pentium 4 Extreme Edition | Pentium Extreme Edition | Pentium D | Pentium 4 6XX | Pentium 4 5XX | |
Processor core | Dothan | Prescott-2M | Smithfield | Smithfield | Prescott-2M | Prescott |
Socket | Socket 479 | LGA775 | LGA775 | LGA775 | LGA775 | LGA775 |
Number of cores | 1 | 1 | 2 | 2 | 1 | 1 |
Core frequency | Up to 2.26 GHz | 3.73 GHz | 3.2 GHz | Up to 3.2 GHz | Up to 3.6 GHz | Up to 3.8 GHz |
Bus frequency | 533 MHz | 1066 MHz | 800 MHz | 800 MHz | 800 MHz | 800 MHz |
Production technology | 0.09- micron, strained silicon | 0.09- micron, strained silicon | 0.09- micron, strained silicon | 0.09- micron, strained silicon | 0.09- micron, strained silicon | 0.09- micron, strained silicon |
Transistors | 140 mln. | 169 mln. | 230 mln. | 230 mln. | 169 mln. | 125 mln. |
Die size | 84 sq.mm | 135 sq.mm | 206sq.mm | 206sq.mm | 135sq.mm | 112sq.mm |
L1 data cache | 32 KB | 16 KB | 2 x 16 KB | 2 x 16 KB | 16 KB | 16 KB |
L1 instructions cache | 32 KB | 12000 uops | 2 x 12000 uops | 2 x 12000 uops | 12000 uops | 12000 uops |
L2 cache | 2048 KB | 2048 KB | 2 x 1024 KB | 2 x 1024 KB | 2048 KB | 1024 KB |
L3 cache | - | - | - | - | - | - |
SIMD-instructions | SSE2/ SSE | SSE3/ SSE2/ SSE | SSE3/ SSE2/ SSE | SSE3/ SSE2/ SSE | SSE3/ SSE2/ SSE | SSE3/ SSE2/ SSE |
EM64T | - | + | + | + | + | Optional |
Hyper-Threading | - | + | + | - | + | + |
Execute Disable Bit | + | + | + | + | + | + |
Intel Enhanced SpeedStep | + | - | + | + | + | - |
So, Pentium M processors use a Quad Pumped Bus analogous to the one employed by Pentium 4 CPUs. What prevents the users from installing the Pentium M on desktop platforms, the marketing restrictions put aside?
First, the Pentium M is inserted into Socket 479 which is pin-compatible neither with LGA775 nor with Socket 478. It seems to be easy to remove this problem by simply adjusting the mainboard’s wiring. But the problem is the input/output buffers of the Pentium M use a different signaling voltage than ordinary chipsets. The I/O buffers of the Pentium 4 use the same voltage as the core, but the Pentium M’s buffers work at a voltage reduced by 1.05V. This is the reason for the Pentium M to be so poorly compatible with classic chipsets.
Anyway, this obstacle proved to be surmountable. Engineers from ASUS developed a special adapter for using Pentium M processors in Socket 478 mainboards based on i875/i865 chipsets.
The ASUS CT-479 adapter solves all the problems concerning the pin assignment differences between Socket 478 and Socket 479 and deals with the electrical compatibility issues. So, if the mainboard’s BIOS supports the Pentium M, you can use Intel’s mobile CPUs in desktop mainboards with the help of this adapter.
There not so many mainboards compatible with the ASUS CT-479, though. There are as yet five of them: ASUS P4P800 SE, ASUS P4P800-VM, ASUS P4C800-E Deluxe, ASUS P4GD1 and ASUS P4GPL-X. These mainboards contain Pentium M-related microcode in their latest BIOS versions which ensures their compatibility (through the ASUS CT-479 adapter) with Pentium M and Celeron M processors based on
The processor installed via the adapter is powered through the mainboard’s standard voltage regulator – the CPU doesn’t “see” the adapter at all. That’s why the ASUS CT-479 does not support Low Voltage and Ultra Low Voltage processors: the power converter of Socket 478 mainboards cannot output the voltage required for them. Besides that, the users have to sacrifice Enhanced Intel SpeedStep technology if they use the adapter – the Pentium M installed into a Socket 478 mainboard via an ASUS CT-479 does not vary its default frequency.
The installation of the converter into the system is simple and intuitive. After you attach it to the mainboard’s Socket 478, you must select the bus frequency of the Pentium M processor (400 or 533MHz) with the jumpers and attach additional power to the converter. The ASUS CT-479 comes with a special cooler for Pentium M processors. This cooler can be mounted on Socket 478 mainboards using the enclosed fasteners.
There’s nothing exceptional about this cooler: it consists of a rather small aluminum heatsink and an 80mm fan with a maximum rotational speed of 3000rpm. Being originally a notebook-oriented processor, Pentium M doesn’t dissipate too much heat and is quite satisfied with such a simple cooling system.
So, the advantages of the ASUS CT-479 are obvious: this adapter allows using Pentium M processors in ordinary Socket 478 mainboards. It means desktop systems with this processor will be able to benefit from a dual-channel memory controller and a full set of additional controllers available on advanced Socket 478 mainboards from ASUS. But you have to sacrifice Enhanced Intel SpeedStep technology to use the adapter.
This review was planned to be a comparison of Intel’s Pentium 4 and Pentium M architectures. To meet this goal we took senior CPU models from both families. The fastest in the Pentium M series is the Pentium M 770 model with a default clock rate of 2.13GHz. But we learned that Intel was going to announce an even faster CPU in this series, with a rating of 780. We were lucky to get a sample of the Pentium M 780 and so we performed our tests on this processor.
Since the Pentium M 780 is a not-yet-announced product, here’s some info on it: the Pentium M 780 is based on the
Pentium M 780 | |
Frequency | 2.26 GHz |
Package | 478-pin PPGA |
Vcore | 1.287V-1.4V |
Bus frequency | 533 MHz |
Typical heat dissipation | 27 W |
Core stepping | C0 |
Max. typical case temperature | 100°C |
L2 cache size | 2MB |
Production technology | 90 nm |
Hyper-Threading Technology support | No |
Intel Extended Memory 64 Technology (EM64T) support | No |
Execute Disable Bit Feature (NX) support | Yes |
Enhanced Intel SpeedStep (EIST) support | Yes |
The Pentium M has a peculiar appearance: Intel’s mobile processors don’t have a heat-spreading cover that protects the die from damage. Mobile CPUs are seldom installed by the end-user, so this cover is not really necessary here.
The diagnostic utility CPU-Z doesn’t yet know about this processor and sticks a wrong rating on it.
But the rest of the information on the screenshots is perfectly true.
Pentium M processors were specifically developed for mobile computers, and low heat dissipation and power consumption were among the design priorities. For example, the maximum thermal design power of the Pentium M 780 is four times lower than that of the Pentium 4 670. But we are more interested in knowing the typical consumption of processors in real-life uses. So we measured the current consumed by the processor (which was running S&M 1.6.0) with the help of a clamp-on ammeter. The results are listed below. The numbers we got do not count in the efficiency of the mainboard’s voltage converter.
As you see, the Pentium M boasts a very low power consumption under high load. It is six times lower than that of senior Pentium 4 models but is also two times lower than that of the Athlon 64 on the new
Now let’s see what power consumption the Pentium M has in the idle mode. Note that we disabled Enhanced Intel SpeedStep technology for the time of our tests for all the processors, but Pentium 4 CPUs drop their frequency to 2.8GHz when idle by means of
The Pentium M is not an unrivalled leader here. The new processors of the Athlon 64 family on the
Before reporting on our practical overclocking experiments with a Pentium M, we want to say that even though we tested the senior model of the series, you should not think that the overclocking potential of this CPU is poor. The Pentium M is just targeted at the mobile sector of the market, and such products must comply with the strict heat dissipation requirements. That is, the frequency growth of the Pentium M series is limited by the maximum typical heat dissipation rather than by the architecture or the current tech process. In other words, the frequency bar of Pentium M processors may go much higher than the frequencies of the current top models of this series.
So, it’s the more interesting to find the frequency limit of the Pentium M. To do this experimentally, we assembled a computer with an ASUS P4C800-E Deluxe mainboard and an ASUS CT-479 adapter. Then, using the cooler enclosed with the adapter, we overclocked our sample of the Pentium M 780. We should note that the ASUS CT-479 somewhat limits the mainboard’s overclocking options. Particularly, the option of adjusting the multiplier coefficient vanishes from the BIOS Setup (this multiplier can normally be reduced below the default value for Pentium M processors that support Enhanced Intel SpeedStep). Moreover, some mainboards with an ASUS CT-479 installed refuse to change the CPU voltage. The ASUS P4C800-E Deluxe, however, was free from the latter disadvantage. The default frequency of the Pentium M 780 is 2.26GHz, and we first of all wanted to know the highest frequency of this processor without increasing the voltage of the core. The default FSB frequency of this processor is 133MHz; the CPU’s default multiplier is 17x.
The Pentium M 780 did permit to increase its operational frequency considerably. Steadily lifting the FSB frequency up, we found the limit at 160MHz. The FSB frequency being 160MHz, the processor worked at 2.72GHz. In other words, the default CPU frequency grew up by 20% at overclocking!
So, the senior model in the Pentium M series has a 20% reserve of frequency. It is natural with a mobile CPU, but it would be a sensation if a senior desktop processor were to show such a good overclockability.
Recalling that Pentium III processors used to overclock better at higher voltages, we decided to give more voltage to our Pentium M, too. Having increased Vcore by 0.1V above the default, we got some better results at overclocking: 166MHz was the maximum FSB frequency at which the processor was stable. That is, the highest stable frequency of the processor with 1.48V Vcore was 2.82GHz. This is 25% above the default frequency of this model!
So, it’s a rewarding business to overclock a Pentium M. Even senior models of this series are capable of working at frequencies high above their default ones.
Obviously, junior models of this family can please you even more at overclocking. A very nice thing about the ASUS CT-479 adapter is that it permits to overclock a Pentium M using almost all of the mainboard’s options. The adapter being absolutely transparent to the CPU and mainboard, you overclock your Pentium M just as you would a regular Socket 478 processor. Of course, the increased voltage and frequency of the processor result in higher heat dissipation and power consumption. For example, the Pentium M consumes as much as 40.8 watts under load if it is clocked at 2.82MHz. This does not fit into the standard thermal design power of this processor.
We can suppose that the overclocking results will be much better if the cooling system is more efficient, but unfortunately you can’t use standard Socket 478 coolers with the Pentium M if you use an ASUS CT-479 converter. So if you’re into serious overclocking, the main problem you’ll be facing is creating a unique and efficient cooling system.
One of the goals of this review is to determine the performance level of the Pentium M processor if it is installed into a desktop computer system by means of an ASUS CT-479 adapter. Considering that a senior Pentium M model and this adapter would cost about $700 together, we will compare the Pentium M 780 with top models from the following desktop CPU series: Pentium 4, Pentium D, Athlon 64, Athlon 64 FX, and Athlon 64 X2.
Even though you can now use the Pentium M in desktop mainboards for enthusiasts, there still remain certain limitations concerning the frequency of the memory subsystem. Particularly, the i875 and i865 chipsets that the mainboards compatible with the ASUS CT-479 are based on support only dual-channel DDR333/DDR266 SDRAM due to the fact that the system bus of modern Pentium M processors is clocked at 533MHz. This deficiency is not a catastrophe, though. Dual-channel DDR333 SDRAM’s bandwidth of 5.3GB/s is quite sufficient for feeding data to the Pentium M’s system bus which has a bandwidth of 4.3GB/s.
We built our test systems out of the following hardware parts:
* DDR400 SDRAM worked as DDR333 SDRAM on the Pentium M platform.
Two properties of the Pentium M processor make it a good runner of office applications. First, the Pentium M has a rather large, 2-megabyte L2 cache. Second, this is a low-latency cache – only 5 cycles. That’s why the Pentium M looks so confident in Business Winstone 2004 which benchmarks the performance of a CPU in such applications as Microsoft Access 2002, Microsoft Excel 2002, Microsoft FrontPage 2002, Microsoft Outlook 2002, Microsoft PowerPoint 2002, Microsoft Project 2002, Microsoft Word 2002, Norton AntiVirus Professional Edition 2003 and WinZip 8.1.
SYSmark 2004 isn’t that optimistic about the performance of the Pentium M in office applications, though. The scripts in this benchmark simulate the user working with several applications at a time. The Pentium M doesn’t have any multi-threading technologies like Hyper-Threading, and its results are consequently not very high.
The result of the Pentium M 780 is rather low, again. The digital content processing applications from this benchmark – Adobe Photoshop 7.0.1, Adobe Premiere 6.50, Macromedia Director MX 9.0, Macromedia Dreamweaver MX 6.1, Microsoft Windows Media Encoder 9 Version 9.00.00.2980, NewTek LightWave 3D 7.5b and Steinberg WaveLab 4.0f – support multi-threading and profit a lot from a high-speed memory subsystem. The system built around the Pentium M has neither.
It’s all absolutely the same in SYSmark 2004.
The popular benchmark PCMark04 is rather skeptical about the Pentium M 780. Why? PCMark04 uses multi-threading but Intel’s mobile processors do not support it in their hardware. This is also why the Pentium 4 processors look so advantageous against AMD’s Athlon 64.
But the Pentium M 780 is among the leaders in 3DMark2001. Could games be this processor’s forte?
The Pentium M 780 is slower than its main rival in 3DMark05, however. We think this is due to our using an AGP graphics card in the Pentium M platform, while the Pentium 4 and Athlon 64 platforms worked with PCI Express x16 graphics.
Well, the Pentium M isn’t brilliant in the CPU tests, either. This time the explanation is simple: these tests perform shaders on the central processor and actively use the FPU which is rather weak in the Pentium M by today’s standards.
The performance of the Pentium M 780 in games is astonishing. The processor based on the Pentium III architecture and oriented towards mobile applications doesn’t just leave behind all the available Pentium 4 models but challenges the Athlon 64 4000+ which is one of the best processors for gamers! We think if the Pentium M had a faster bus and worked with dual-channel DDR400 SDRAM, it would be indisputably the best gaming processor of today.
However strange it may seem, the Pentium M 780 with slower DDR333 SDRAM outperforms the entire Pentium 4 line-up in WinRAR. Its large and fast L2 cache obviously helps a lot here.
Even though the Pentium M 780 is slower than any Pentium 4 at encoding audio into the MP3 format, it is faster than any single-core Athlon 64.
The Pentium 4 remains the best processor for video encoding, while the Pentium M fails in tasks of that type. The low performance of the FPU, the lack of Hyper-Threading and SSE3 all lead to the Pentium M being very poor in this test.
Well, it’s not so bad for the Pentium M 780 when we use certain codecs, like XviD in this example.
The Pentium M performs quite well in Photoshop and After Effects. This processor is on the same level as the senior Athlon 64 models, but is inferior to the Pentiums 4.
In Adobe Premier, however, the mobile processor from Intel fails completely.
The Pentium M performs quite expectedly in Sciencemark. This test relies heavily on the floating-point unit, and the Pentium M’s FPU is weaker than the Pentium 4’s, not to mention the Athlon 64’s.
Like in computational tasks, the performance of the Pentium M is very low at doing final rendering.
The ASUS CT-479 adapter we have examined today is a truly innovative solution. And it is currently the best solution for bringing Pentium M processors to desktop computers. This adapter is compatible with a number of Socket 478 mainboards from ASUS and allows using the Pentium M with dual-channel memory and all the additional controllers available on these mainboards. Besides that, the ASUS CT-479 does not prevent overclocking, but leaves the user with almost all the overclocking options implemented in the mainboards’ BIOSes.
On the other hand, it is hard to say a definite yes or no to the “desktop” Pentium M. The indisputable advantages of this series are very low heat dissipation and power consumption, which allows building quiet and economical systems around these CPUs. The performance of such a system would be quite high, but not the best available today.
The Pentium M architecture, a descendant of the Pentium III architecture, has certain drawbacks, too. For example, these processors work with a rather slow system bus, have a low-performance FPU, lack the support of SSE3 as well as 64-bit extensions to the x86 architecture. That’s why Pentium M processors cannot rival modern Pentium 4 and Athlon 64 models in many applications.
Games are where the Pentium M looks most impressive, of course. Thanks to its fast and large cache memory, this processor is no slower than the senior Athlon 64 models in gaming applications, and gamers might appreciate this.
Yet we wouldn’t recommend the Pentium M even to this category of users. Yes, the Pentium III architecture looks quite appealing, but it still needs some tweaking to be efficient in modern desktop systems. And fortunately Intel has some plans on making the Pentium M better: the dual-core processor codenamed Yonah and scheduled for the next year is going to have the improvements we have mentioned above.
