Intel takes the wraps off the latest version of the Pentium M, previously codenamed Dothan. This new design moves the Pentium M to 90-nanometer manufacturing process, pushes up clock rates, and doubles the L2 cache. While none of the changes in Dothan can be called revolutionary, it appears that Intel has improved key areas of the original Banias design from lessons learned in the field.
What is L2 Cache? (Level 2 Cache) - A piece of fast memory that sits between the L1 cache of the processor and main memory. It is usually larger than L1 cache, and the L1 cache checks the L2 cache before going to main memory for data (unless the L1 and L2 caches are unified--see unified cache). Nowadays L2 caches are almost always on the same die as the processor, but they can be off-chip. An on-die L2 cache is a faster alternative to an SRAM cache, particularly as CPU clock speeds continue to increase.
The most important entries here are the changes in the L1 and L2 cache sizes, where the L1 is 4X bigger and the L2 doubles in size. In fact, the doubling of the L2 cache probably accounts for much of the 81% increase in transistor count. Dothan also offers about an 18% higher peak clock rate, as well as a lower thermal envelope, thanks to the move to Intel's 90-nanometer manufacturing process.
The biggest new feature in Dothan is the big L2 cache, which is the same size as that found in Intel's Pentium 4 Extreme Edition.
The two test systems
Dell Latitude D600 IBM T40
CPU 1.4GHz Banias with 1MB L2 and 8KB L1 caches 1.7GHz Dothan with 2MB L2 and 32KB L1 caches
Chipset Intel 855 chipset Intel 855 chipset
Memory 512MB 512MB
Graphics ATI Mobility Radeon 9000 GPU ATI Mobility Radeon 7500 GPU
Hard Drive Hitachi HK80; 40GB; 5400RPM; 8MB buffer Fujitsu 40GB; 5400RPM; 8MB buffer
Operating System Windows XP Pro with SP1 Windows XP Pro with SP1
Hard drive performance can often be a factor in testing and because laptop hard drives tend to have lower spin-rates, they can often be one of the factors gating performance. Given that the two systems' hard drives have identical spec's (5,400RPM, 8MB buffer), we believe the performance delta is due in large part to the 2X larger L2 cache. On certain tests, the bulk of the workload can sit in the L2, which minimizes system memory touches. Again, considering that we were testing the entry-level 735 model, and that the top-end 755 model will offer up 18% more clock speed, this bodes very well for content creators looking to go mobile and still get some work done.
Given the Dothan system's 21% clock advantage, the 18% performance gain seen here is actually quite impressive. When changing just the clock rate (and not the amount of L1/L2 cache), it's pretty rare to see performance scale linearly with clock speed. While Dothan didn't scale point-for-point versus its clock advantage, it did come awfully close.
While the business application scaling was interesting, the real eye-opener was the performance delivered on content creation apps. The Dothan CPU holds a 21% clock advantage versus the Banias test system, but we saw better-than-linear scaling on Content Creation Winstone. The Dothan system finishes with a 24% performance advantage.
What about game performance? We didn't run game tests on these systems because the Dothan system, an IBM ThinkPad T40, came with a GPU that's three-generations old. For corporate road dogs, the Mobility Radeon 7500 represents a perfectly competent graphics solution. But for anyone looking to play 3D games, this past-its-prime GPU isn't up to the task of running many current titles. We look forward to systems from the likes of Dell, VoodooPC, HP, and Gateway (Hey!!! Forget them ...we have it now!!!) that are more consumer-focused and use more robust mobile GPUs like nVidia's GeForce 5700 Go and ATI's Mobility Radeon 9700. Given the Dothan CPU's performance on media applications and its ample L2 cache, we believe it will be a solid gaming CPU.
Halo : Combat Evolved - 1024 x 768
(Higher scores mean better performance)
Intel Pentium 4 3.2 GHz 26.7
AMD Athlon64 1.8 GHz 23.1
Intel Pentium-M 735 (1.7 GHz) 24.4
0 35
Unreal Tournament 2004 - 1024 x 768 - Rankin
(Higher scores mean better performance)
Intel Pentium 4 3.2 GHz 100.1
AMD Athlon64 1.8 GHz 84.9
Intel Pentium-M 735 (1.7 GHz) 99.4
0 125
PainKiller City Of Water - 1024 x 768
(Higher scores mean better performance)
Intel Pentium 4 3.2 GHz 72.2
AMD Athlon64 1.8 GHz 69.0
Intel Pentium-M 735 (1.7 GHz) 68.2
0 100
Graphics above: Game PC
GEN-X-PC Centrino Dothan with ATI Radeon 9700 M11 GPU
Majority of above verbage from: ExtremeTech.com
FAQ's
How do Intel® Centrino™ mobile technology-based systems deliver high performance, even at relatively lower frequencies?
There are many ways to influence a system's performance, one of which is the processor's MHz. Intel Centrino mobile technology benefits from a unique micro-architecture, optimized for the mobile segment, to deliver breakthrough mobile performance with low power characteristics through efficient execution and advanced power-saving techniques.
The design focuses on three main areas, efficient execution engine, enhanced data bandwidth and advanced power control. This combination delivers the outstanding mobile performance that you ordinarily might associate with higher MHz, but at much lower power consumption. MHz remains the relative measure of goodness within each architectural family.
Examples of 'Efficient Execution' include, Advanced Branch Prediction, Micro-Ops Fusion & Dedicated Stack Manager, 'Enhanced Data Bandwidth" includes Larger 1MB Cache, High Performance PSB, and Advanced Pre-Fetch Logic, while example of 'Advanced Power Control' include fine grain Aggressive Clock Gating, and Enhanced Intel SpeedStep Technology.
If Intel® Celeron® M processors and Intel® Centrino™ mobile technology are both part of Intel's mobility family, what are the differences?
Intel® Centrino™ mobile technology represents a combination of Intel's best mobile technologies (Intel® Pentium® M processor, Intel® 855 chipset, and Intel® PRO/Wireless 2100 network connection) delivering all four vectors of mobility: performance, integrated wireless, enables extended battery life, enables thinner/lighter form factors.
The Intel® Celeron® M brand represents only the Intel® Celeron® M processor. Designed for mobility, the Intel® Celeron® M processor delivers exceptional value with a balance of mobile processor technology enabling thinner and lighter systems.
What is the power-optimized processor system bus?
The power-optimized 400 MHz processor system bus remains powered down until it senses incoming data form the chipset, allowing to the processor to consume less power. In a typical microarchitecture, a processor has its bus turned on even when it is not in use. With the Pentium M processor and Celeron M processor, portions of the bus are turned on only when they are needed. Architectural and circuit innovations enabled this power-optimized processor system bus technology which lowers power through reduced voltage swing and tighter buffer management.
What is the large, power-aware 1MB Secondary Cache?
The Pentium M processor includes a 1MB secondary cache and Celeron M processor includes 512K secondary cache. The large cache allows a significant reduction in memory data latency providing a big performance improvement. The power-aware cache implements several features to reduce cache power consumption. Traditional microprocessors run the cache as fast as possible, the processor cache on the processor runs slightly slower to save energy and cut down on electricity leakage enabling longer battery life. Special circuit and micro-architectural innovations were implemented in order to reduce power consumption. For example the cache unit keeps track of the last entry that was accessed such that repeating accesses to the same location will not have to lookup the array, thus eliminating a high power operation.
What is Enhanced Intel SpeedStep® Technology with Multiple Voltage / Frequency Operating Points?
Mobile Intel Pentium 4 Processor-M supports Enhanced Intel SpeedStep® technology allowing the processor to switch between only two core performance frequencies.
Intel Pentium M processors add new capabilities to Enhanced Intel SpeedStep technology with multiple voltage / frequency operating points. This means that dynamic transitions will happen at smaller intervals between the Battery-Optimized mode (lowest voltage / frequency) and the Performance-Optimized mode (highest voltage / frequency), enabling higher performance and lower power for each workload. With dynamic switching capability mobile systems can switch between the multiple operating points based on CPU utilization, without user intervention. The result is that the user observes higher performance and extended battery-life automatically. Enhanced Intel SpeedStep technology with multiple voltage / frequency operating points enables optimum performance at the lowest power whether connected to AC or Battery Power, resulting in a better user experience with no battery life degradation.