The Centrino platform has just received a major revision. Tim Dean peers inside Sonoma and takes a look at what we can expect.
The Centrino was an interesting departure from Intel's normal marketing modus operandi. Instead of promoting the CPU, chipset and networking hardware under discreet monikers, the Centrino was an umbrella term that applied to a whole bundle of individual components. Assemblers could choose to mix and match components, but they would only be able to display the Centrino logo if all three elements were present: processor, chipset and wireless module.
Intel is continuing this trend with the recent launch of the next generation of the Centrino platform, codenamed Sonoma. More than just a slight update, Sonoma includes revisions to all the core components, and adds some new features on top.
The brainsAt the core of the Sonoma platform is the Dothan Pentium M processor, which was launched as a part of the Centrino package mid 2004. The Dothan represents a moderate update over its predecessor, the Banias, and will be the last of the single core mobile CPUs. The Dothan is manufactured at 90nm, compared to the 130nm of the previous generation Banias. A die shrink is always a good thing, especially for a mobile processor, as it reduces power consumption as well as heat generated. Dothan also includes Enhanced SpeedStep to further conserve power by using constant minor voltage adjustments to give the CPU only as much power as it needs at any one time. It also supports a Deeper Sleep mode when idle which consumes very little power. Intel claims these features, along with the die shrink, mean the Dothan consumes the same amount of juice as the Banias, even at higher frequencies.
Another significant change with the Sonoma chipsets is an increase in bus speed from the 400MHz of the Centrino up to 533MHz. The front side bus speed, and its corresponding influence on memory bandwidth, was one of the areas where the Centrino and the Pentium M were being left well and truly behind by the desktops, so this increase in speed is quite significant. The increase in front side bus speed also comes along with the addition of dual channel DDR2 533 support. This will make the Sonoma a better performer in memory intensive applications, such as games, but also in highly multitasking environments.
Some versions of the new Dothan will also sport the XD, execute disable protection, which works with a compatible OS, such as Windows XP Service Pack 2, to prevent buffer overruns (see Tech Horizons, September 2004). Buffer overruns are a popular exploit used by virus writers to infect your system, and XD is now becoming a standard part of many processors, including the Pentium 4 and AMD's Athlon 64.
Otherwise, besides the obligatory increases in frequency, up to 2.26GHz, the Dothan is very similar to its predecessors, although it will likely be the last of its kind, with Intel going down the dual core route with the upcoming Yonah, which is expected some time late 2005 to early 2006.
The glueOne of the main features of the Sonoma is a chipset upgrade, called Alviso, bringing it in line with the latest desktop features. The Alviso is based on the desktop 915 chipset, with three versions available depending on what features are built in. At the top end is the 915GM, which can handle both 400MHz and 533MHz front side bus speeds, along with dual channel 533MHz DDR2, and has integrated graphics running at a variety of speeds up to 320MHz. Furthermore, if you don't want the integrated graphics, the 915GM has a PCI-Express x16 slot for a discreet graphics card. The 915GM is intended for large form factor desktop replacements, where performance and features are more important than power consumption or battery life.
For small form factor systems, there's the trimmed down 915GMS, which forgoes the PCI-Express slot in favour of the integrated graphics, and only supports a 400MHz front side bus speed and single channel 400MHz DDR2. However, it comes in a smaller package size, measuring only 27mm x 27mm compared to the 37.5mm x 40mm of the 915GM, making it ideal for ultra portables.
The final iteration is the 915PM, which is identical to the 915GM except it doesn't have integrated graphics, requiring the assembler to add their own PCI Express x16 card. This option is for the vendors who want to include a high-performance mobile graphics chip, such as from ATI or NVIDIA, or they want to include another low cost module.
The integrated graphics in the 915GM and 915GMS, called the Intel Graphics Media Accelerator 900 (GME 900), has also received an update to bring it closer in line with the latest desktop offerings. Primarily this means including DirectX 9.0 support, which is up from the DirectX 7.1 support of the last generation 855GME chipset. Pixel pipelines have also been increased from one to four, memory bandwidth is up from 6.4GB/s to 8.5GB/s, and support has been added for hardware Pixel Shaders 2.0, although Vertex Shaders are still handled in software, which is considerably slower than a hardware implementation. This should make the GME 900 a slightly more viable proposition for gaming, although by specs alone it should fall well short of powerhouse discreet chips from ATI or NVIDIA when it comes to 3D.
The ICH6-M I/O chip packs in PCI-Express and Serial ATA interconnects, bringing it up to date with the latest in desktop technology. While there aren't many peripherals and hard disks for the mobile platform using these interconnects, the technologies are rapidly maturing in the desktop space, and we can expect to see them very soon for portables. As such, we should start seeing an even faster migration away from the old PCI and parallel ATA to PCI-Express and Serial ATA in the near future.
As the chipset is based around the 915, it also includes the 915's Intel High Definition Audio (HDA), which replaces the ageing AC'97 specification. HDA includes 32-bit multi channel output, along with nifty features like port retasking, so a single port can be used for different outputs depending on your configuration.
One of the primary features of the Centrino was built in wireless, with the original Centrino sporting 802.11b support, with 802.11a and 802.11g coming later down the track. One issue that Intel had in motivating notebook assemblers to keep the triumvirate of Centrino components together was the lack of a single combined 802.11a/b/g module up until the end of last year. If an assembler wanted to provide comprehensive wireless support, it was forced to use a third party wireless chip, which would forfeit the chance of using the Centrino moniker. The Sonoma uses the same PRO/Wireless 2915ABG Network Connection that was introduced for the Centrino in October 2004.
Smaller and smallerOne interesting feature to be included in the Sonoma is support for the new ExpressCard format. ExpressCard is similar to PC Card technology, and has been developed by many of the member companies of the PCMCIA (Personal Computer Memory Card International Association) standards body. So, while it's not an official PCMCIA standard, it's sure to gain widespread acceptance in the market, especially as it's now being built in to Sonoma notebooks.
ExpressCard has a couple of key benefits over PC Cards. First off is the size. The smallest module, called ExpressCard/34 as it's only 34mm wide, is nearly half the size of a PC Card, and is ideal for simple peripherals, such as network adapters. There is also a larger size, the ExpressCard/54, which is the same width as a PC Card, although it's still slightly shorter. This form factor is for applications that require a physically larger interface, such as media card adapters as well as micro hard drives.
The other main benefit of ExpressCard is that it connects to the PC either through PCI-Express or USB 2.0, depending on which interface is the most appropriate. PCI-Express offers higher performance, while USB 2.0 is a simpler and cheaper interface. Both are hot swappable, and all ExpressCard slots will support either interface seamlessly.
Mobile to desktopIn an interesting twist of fate, some of the innovations that have taken place on the mobile platform are actually moving back up the chain to the desktop arena. Usually cutting edge technology is developed for the desktop first, then adapted for mobile products. In this case, however, some of the same challenges that have always faced mobile systems, namely heat and power consumption, are starting to become significant issues for desktops.
As such, Intel will be brining the Enhanced SpeedStep technology to the 6xx series of Pentium 4 processors. These CPUs will have a 2MB L2 cache, and will also be the first desktop chips to use the EM64T 64-bit memory extensions, allowing them to access more than 4Gb of RAM. However, Intel has identified that power consumption, and the subsequent heat generation, are getting to be significant issues.
The idea is that Enhanced SpeedStep technology, which constantly adjusts the voltage depending on processor load, will reduce power consumption, and as a consequence the system should also be quieter due to the fact that less active cooling fans will be needed. This doesn't mean the processor will have insufficient cooling if it's running at full power for a length of time, just that variable speed fans will throttle down in all but the most intense circumstances. We can also expect Enhanced SpeedStep to work its way through the rest of Intel's portfolio of processors in coming years as well.
Issue: 133 | February, 2012