XScale
The XScale, a microprocessor core, is Intel's implementation of the 5th generation of the ARM architecture. It is based on the v5TE ISA without the floating point instructions. XScale uses a 7 stage integer and an 8 stage memory Superpipelined RISC architecture. It is the successor to the Intel StrongARM line of microprocessors and microcontrollers, which Intel acquired from DEC's Digital Semiconductor division as the side-effect of a lawsuit between the two companies. Intel used the StrongARM to replace their ailing line of outdated RISC processors, the i860 and i960.
All the generations of XScale are 32-bit ARM v5TE processors manufactured with a 0.18 µm process and have a 32 KiB data cache and a 32 KiB instruction cache (this would be called a 64 KiB Level 1 cache on other processors). They also all have a 2 KiB mini-data cache.
Processor Families
The XSCALE core is used in a number of microcontroller families manufactured by Intel, notably:
- Application Processors (with the prefix PXA). There are three generations of XScale Application Processors, described below: PXA210/PXA25x, PXA26x and PXA27x.
- I/O Processors (with the prefix IOP)
- Network Processors (with the prefix IXP)
- Control Plane Processors (with the prefix IXC).
There are also standalone processors: the 80200 and 80219 (targeted primarily at PCI applications).
PXA Family
PXA210/PXA25x
The PXA210 was Intel's entry level XScale targeted at mobile phone applications. It was released with the PXA250 in February 2002 and comes clocked at 133 MHz and 200 MHz.
The PXA25x family consists of the PXA250 and PXA255. The PXA250 was Intel's first generation of XScale processors. There was a choice of three clock speeds: 200 MHz, 300 MHz and 400 MHz. It came out in February 2002. In March 2003, the revision C0 of the PXA250 was renamed to PXA255. The main differences were a doubled bus speed (100 MHz to 200 MHz) for faster data transfer, lower voltage (only 1.3 V at 400 MHz) for lower power consumption and writeback functionality for the data cache, the lack of which had severely impaired performance on the PXA250.
PXA26x
The PXA26x family consists of the PXA260 and PXA261-PXA263. The PXA260 is a stand-alone processor clocked at the same as the PXA25x, but features a TPBGA package which is about 53% smaller then the PXA25x's PBGA package. The PXA261-PXA263 are the same as the PXA260 but have Intel StrataFlash memory stacked on top of the processor in the same package; 16 MiB of 16-bit memory in the PXA261, 32 MiB of 16-bit memory in the PXA262 and 32 MiB of 32-bit memory in the PXA263. The PXA26x family was released in March 2003.
PXA27x
The PXA27x family (code-named Bulverde) consists of the PXA270 and PXA271-PXA272 processors. This revision is a huge update to the XScale family of processors. The PXA270 is clocked in four different speeds: 312 MHz, 416 MHz, 520 MHz and 624 MHz and is a stand-alone processor with no packaged memory. The PXA271 can be clocked to 312 MHz or 416 MHz and has 32 MiB of 16-bit stacked StrataFlash memory and 32 MiB of 16-bit SDRAM in the same package. The PXA272 can be clocked to 312 MHz, 416 MHz or 520 MHz and has 64 MiB of 32-bit stacked StrataFlash memory.
Intel also added many new technologies to the PXA27x family such as:
- Wireless SpeedStep: the operating system can clock the processor down based on load to save power.
- Wireless MMX: 43 new SIMD instructions containing the full MMX instruction set and the integer instructions from Intel's SSE instruction set along with some instructions unique to the XScale. Wireless MMX provides 16 extra 64-bit registers that can be treated as an array of two 32-bit words, four 16-bit halfwords or eight 8-bit bytes. The XScale core can then perform up to eight adds or four MACs in parallel in a single cycle. This capability is used to boost speed in decoding and encoding of multimedia and in playing games.
- Additional peripherals, such as an USB-Host interface and a camera interface.
- Internal 256 KiB SRAM to reduce power consumption and latency.
The PXA27x family was released in April 2004. Along with the PXA27x family Intel released the 2700G embedded graphics co-processor.
PXA29x Monahans
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Toradex_Colibri_XScale_Monahans_PXA290.jpg/280px-Toradex_Colibri_XScale_Monahans_PXA290.jpg)
In August 2005 Intel announced the successor to Bulverde, codenamed Monahans. They demoed it showing its capability to play back high definition encoded video on a PDA screen. The new processor was shown clocked at 1.25 GHz but Intel said it only offered a 25% increase in performance (800 MIPS for the 624 MHz PXA270 processor vs 1000 MIPS for 1.25 GHz Monahans). An announced successor to the 2700G graphics processor, code named Stanwood, has since been cancelled. Some of the features of Stanwood are integrated into Monahans. For extra graphics capabilities, Intel recommends third party chips like the Nvidia GoForce chip family.
IXC Family
IXC1100
The IXC1100 processor features clock speeds at 266, 400, and 533 MHz, a 133 MHz bus, 32 KiB of instruction cache, 32 KiB of data chace, and 2 KiB of mini-data cache. It is also designed for low power consumption, using 2.4 W at 533 MHz. The chip comes in the 35 mm PBGA package.
IOP Family
The IOP line of processors is designed to allow computers and storage devices to transfer data and increase performance by offloading I/O functionality from the main CPU of the device. The IOP3XX processors are based on the XScale architecture and designed to replace the older 80219 processor and i960 family of chips. There are seven different IOP processors currently available: IOP303, IOP310, IOP321, IOP331, IOP332, and IOP333. Clock speeds range from 100 MHz to 800 MHz. The processors also differ in PCI bus speed, memory type, and maximum memory allowable.
IXP Family
The IXP line of processors is designed as a network and control plane processor. Its main applications include VoIP equipment, network switches, and wireless networking products. There are currently eight different processors avaiable in the IXP family: IXP420, IXP421, IXP422, IXP423, IXP425, IXP455, IXP460, and IXP465. They vary in intended application and performance specifications.
Applications
XScale microprocessors can be found in products such as the popular RIM BlackBerry handheld, the Dell Axim family of Pocket PCs, most of the Zire, Treo and Tungsten Handheld lines by Palm, later versions of the Sharp Zaurus, the Motorola A780, the Acer n50, the Compaq iPaq 3900 series and many other PDAs. It is used as the main CPU in the Iyonix desktop computer running RISC OS, and the NSLU2 (Slug) running a form of Linux. The XScale is also used in devices such as PVPs (Portable Video Players), PMCs (Portable Media Centres), including the Creative Zen Portable Media Player, and industrial embedded systems, including the Toradex Colibri single board computer. Apple's recent strategic partnership with Intel has fueled rumors that XScale processors will be found in future iPod products.
At the other end of the market, the XScale IOP33x Storage I/O processors are used in some Intel Xeon-based server platforms.
External links
- Intel XScale Technology Overview
- Intel StrataFlash Memory
- Intel XScale PXA270 and Monahans PXA29X development boards by Toradex of Switzerland
- Publicly Available Devices Based on Intel XScale® Technology
- Embedded ToolsmithsJTAG Emulator, JTAG Flash Programmer, JTAG Debugger for XScale Processors.