Gecko's CPU Library

Intel XScale (PXA, IXC, IOP, IXP) processors

Introduction: February 2002


The XScale, a microprocessor core, was Marvell's (formerly Intel's) implementation of the fifth generation of the ARM architecture, and consisted of several distinct families: IXP, IXC, IOP, PXA and CE. The PXA family was sold to Marvell Technology Group in June 2006.

The XScale architecture was based on the ARMv5TE ISA without the floating point instructions. XScale used a seven-stage integer and an eight-stage memory superpipelined RISC architecture. It was 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 Intel used the StrongARM to replace their ailing line of outdated RISC processors, the i860 and i960.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 were 32-bit ARMv5TE processors manufactured with a 0.18 µm process and have a 32KB data cache and a 32KB instruction cache (this would be called a 64KB Level 1 cache on other processors). They also all have a 2KB mini-data cache.

The XScale core was used in a number of microcontroller families manufactured by Intel and Marvell, notably:
- Application Processors (with the prefix PXA). There were four generations of XScale Application Processors, described below: PXA210/PXA25x, PXA26x, PXA27x, and PXA3xx.
- Control Plane Processors (with the prefix IXC)
- I/O Processors (with the prefix IOP)
- Network Processors (with the prefix IXP)
- Consumer Electronics Processors (with the prefix CE)
- There are also standalone processors: the 80200 and 80219 (targeted primarily at PCI applications)

The PXA family

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 133MHz and 200MHz.

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: 200MHz, 300MHz and 400MHz. 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 (100MHz to 200MHz) for faster data transfer, lower core voltage (only 1.3V at 400MHz) for lower power consumption and writeback functionality for the data cache, the lack of which had severely impaired performance on the PXA250.

The PXA26x family consisted of the PXA260 and PXA261-PXA263. The PXA260 was a stand-alone processor clocked at the same frequency as the PXA25x, but features a TPBGA package which was about 53% smaller than the PXA25x's PBGA package. The PXA261-PXA263 were the same as the PXA260 but had Intel StrataFlash memory stacked on top of the processor in the same package; 16MB of 16-bit memory in the PXA261, 32MB of 16-bit memory in the PXA262 and 32MB of 32-bit memory in the PXA263. The PXA26x family was released in March 2003.

The PXA27x family (code-named Bulverde) consisted of the PXA270 and PXA271-PXA272 processors. This revision was a huge update to the XScale family of processors. The PXA270 was clocked in four different speeds: 312MHz, 416MHz, 520MHz and 624MHz and was a stand-alone processor with no packaged memory. The PXA271 was clocked to 312MHz or 416MHz and had 32MB of 16-bit stacked StrataFlash memory and 32MB of 16-bit SDRAM in the same package. The PXA272 was clocked to 312MHz, 416MHz or 520MHz and has 64MB of 32-bit stacked StrataFlash memory.

Intel also added many new technologies to the PXA27x family such as:
- Wireless SpeedStep: the operating system was able to 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 provided 16 extra 64-bit registers that could be treated as an array of two 32-bit words, four 16-bit halfwords or eight 8-bit bytes. The XScale core was then able to perform up to eight adds or four MACs in parallel in a single cycle. This capability was used to boost speed in decoding and encoding of multimedia and in playing games.
- Additional peripherals, such as a USB-Host interface and a camera interface
- Internal 256KB 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.

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 1.25GHz but Intel said it only offered a 25% increase in performance (800MIPS for the 624MHz PXA270 processor vs. 1000MIPS for 1.25GHz Monahans). An announced successor to the 2700G graphics processor, code named Stanwood, has since been canceled. 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.

In November of 2006, Marvell Semiconductor officially introduced the Monahans family as Marvell PXA320, PXA300, and PXA310. PXA320 was shipped in high volume, and was scalable up to 806MHz. PXA300 and PXA310 delivered performance "scalable to 624MHz", and were software-compatible with PXA320.

The PXA90x was released by Marvell and combines an XScale Core with a GSM/CDMA communication module.

The IXC family

The IXC1100 processor featured clock speeds at 266, 400, and 533MHz, a 133MHz bus, 32KB of instruction cache, 32KB of data cache, and 2KB of mini-data cache. It was also designed for low power consumption, using 2.4W at 533MHz. The chip came in the 35 mm PBGA package.

The IOP family

The IOP line of processors was designed to allow computers and storage devices to transfer data and increased performance by offloading I/O functionality from the main CPU of the device. The IOP3XX processors were based on the XScale architecture and designed to replace the older 80219 processor and i960 family of chips. There were ten different IOP processors available: IOP303, IOP310, IOP315, IOP321, IOP331, IOP332, IOP333, IOP341, IOP342 and IOP348. Clock speeds ranged from 100MHz to 1.2GHz. The processors also differed in PCI bus type, PCI bus speed, memory type, maximum memory allowable, and the number of processor cores.

The IXP family

The XScale core was utilized in the second generation of Intel's IXP network processor line, while the first generation used StrongARM cores. The IXP network processor family ranged from solutions aimed at small/medium office network applications , IXP4XX, to high performance network processors such as the IXP2850, capable of sustaining up to OC-192 line rates. In IXP4XX devices the XScale core was used as both a control and data plane processor, providing both system control and data processing. The task of the XScale in the IXP2XXX devices was typically to provide control plane functionality only, with data processing performed by the microengines, examples of such control plane tasks included routing table updates, microengine control, memory management.

XScale microprocessors could 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 was used as the main CPU in the Iyonix PC desktop computer running RISC OS, and the NSLU2 (Slug) running a form of Linux. The XScale was also used in devices such as PVPs (Portable Video Players), PMCs (Portable Media Centres), including the Creative Zen Portable Media Player and Amazon Kindle E-Book reader, and industrial embedded systems. Apple's iPhone and recent iPod models also use XScale processors. At the other end of the market, the XScale IOP33x Storage I/O processors were used in some Intel Xeon-based server platforms.

On June 27, 2006, the sale of Intel's XScale PXA mobile processor assets was announced. Intel agreed to sell the XScale PXA business to Marvell Technology Group for an estimated $600 million in cash and the assumption of unspecified liabilities. The move was intended to permit Intel to focus its resources on its core x86 and server businesses. The acquisition was completed on November 9, 2006. Intel was expected to continue manufacturing XScale processors until Marvell secures other manufacturing facilities, and continued manufacturing and selling the IXP and IOP processors, as they were not part of the deal.

Source: Wikipedia, the free encyclopedia.