XScale
XScale is a microarchitecture for central processing units initially designed by Intel implementing the ARM v5 instruction set. XScale comprises several distinct families: IXP, IXC, IOP, PXA and CE, with some later models designed as system-on-a-chip. Intel sold the PXA family to Marvell Technology Group in June 2006. Marvell then extended the brand to include processors with other microarchitectures, like Arm's Cortex.
The XScale architecture is based on the ARMv5TE ISA without the floating-point instructions. XScale uses a seven-stage integer and an eight-stage memory super-pipelined microarchitecture. It is the successor to the Intel StrongARM line of microprocessors and microcontrollers, which Intel acquired from DEC's Digital Semiconductor division as part of a settlement of a lawsuit between the two companies. Intel used the StrongARM to replace its ailing line of outdated RISC processors, the i860 and i960.
All the generations of XScale are 32-bit ARMv5TE processors manufactured with a 0.18 μm or 0.13 μm process and have a 32 KB data cache and a 32 KB instruction cache. First- and second-generation XScale multi-core processors also have a 2 KB mini data cache. Products based on the third-generation XScale have up to 512 KB unified L2 cache.
Processor families
The XScale core is used in a number of microcontroller families manufactured by Intel and Marvell:- Application processors. There are four generations of XScale application processors, described below: PXA210/PXA25x, PXA26x, PXA27x, and PXA3xx.
- I/O processors.
- Network processors.
- Control plane processors.
- Consumer electronics processors.
PXA
PXA System on a Chip products were designed in Austin, Texas. The code-names for this product line are small towns in Texas, primarily near deer hunting leases frequented by the Intel XScale core and mobile phone SoC marketing team. PXA System on a Chip products were popular on smartphones and PDAs during 2000 to 2006.Under Intel
PXA16x
PXA16x is a processor designed by Marvell, combining the earlier Intel designed PXA SoC components with a new ARMv5TE CPU core named Mohawk or PJ1 from Marvell's Sheeva family instead of using wdc Xscale or ARM design. The CPU core is derived from the Feroceon core used in Marvell's embedded Kirkwood product line, but extended for instruction level compatibility with the XScale IWMMX.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 internal bus speed for faster data transfer, lower core voltage for lower power consumption and writeback functionality for the data cache, the lack of which had severely impaired performance on the PXA250.
Intel XScale Core Features :
- ARMv5TE
- ARM Thumb
- ARM DSP
- L1 32-KByte data and instruction cache
PXA26x
PXA27x
The PXA27x family 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 13, 104, 208 MHz or 416 MHz and has 32 MB of 16-bit stacked StrataFlash memory and 32 MB of 16-bit SDRAM in the same package. The PXA272 can be clocked to 312 MHz, 416 MHz or 520 MHz and has 64 MB of 32-bit stacked StrataFlash memory.Intel also added many new technologies to the PXA27x family such as:
- 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 a USB-Host interface and a camera interface.
- Internal 256 KB SRAM to reduce power consumption and latency.
PXA3xx
In August 2005 Intel announced the successor to Bulverde, codenamed Monahans.Demonstrated 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.
An announced successor to the 2700G graphics processor, code named Stanwood, was later canceled. sd features of Stanwood are integrated into Monahans. For extra graphics capabilities, Intel recommends third-party chips like the Nvidia GoForce chip family.
In November 2006, Marvell Semiconductor officially introduced the Monahans family as Marvell PXA320, PXA300, and PXA310. PXA320 is currently shipping in high volume, and is scalable up to 806 MHz. PXA300 and PXA310 deliver performance "scalable to 624 MHz", and are software-compatible with PXA320.
PXA800F
Codenamed Manitoba, Intel PXA800F was a SoC introduced by Intel in 2003 for use in GSM- and GPRS-enabled mobile phones. The chip was built around an XScale processor core, the likes of which had been used in PDAs, clocked at 312 MHz and manufactured with a 0.13 μm process, with 4 MB of integrated flash memory and a digital signal processor.A prototype board with the chip was demoed during the Intel Developer Forum. Intel noted it was in talks with leading mobile phone manufacturers, such as Nokia, Motorola, Samsung, Siemens and Sony Ericsson, about incorporating Manitoba into their phones.
O2 XM, released in 2005, was the only mobile phone with a documented use of the Manitoba chip. An Intel executive stated that the chip version used in the phone was reworked to be less expensive than the initial one.
PXA90x
The PXA90x, codenamed Hermon, was a successor to Manitoba with 3G support. The PXA90x is built using a 130 nm process. The SoC continued being marketed by Marvell as they acquired Intel's XScale business.Under Marvell
PXA930/935
The PXA930 and PXA935 processor series were again built using the Sheeva microarchitecture developed by Marvell but upgraded to ARMv7 instruction set compatibility. This core is a so-called Tri-core architecture codenamed Tavor; Tri-core means it supports the ARMv5TE, ARMv6 and ARMv7 instruction sets. This new architecture was a significant leap from the old Xscale architecture. The PXA930 uses 65 nm technology while the PXA935 is built using the 45 nm process.The PXA930 is used in the BlackBerry Bold 9700.