StrongARM

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DEC StrongARM SA-110 microprocessor

The StrongARM is a family of computer microprocessors developed by Digital Equipment Corporation and manufactured in the late 1990s which implemented the ARM v4 instruction set architecture. It was later acquired by Intel in 1997 from DEC's own Digital Semiconductor division as part of a settlement of a lawsuit between the two companies over patent infringement.[1] Intel then continued to manufacture it before replacing it with the StrongARM-derived ARM-based follow-up architecture called XScale in the early 2000s.

History

According to Allen Baum, the StrongARM traces its history to attempts to make a low-power version of the DEC Alpha, which DEC's engineers quickly concluded was not possible. They then became interested in designs dedicated to low-power applications which led them to the ARM family. One of the only major users of the ARM for performance-related products at that time was Apple, whose Newton device was based on the ARM platform. DEC approached Apple wondering if they might be interested in a high-performance ARM, to which the Apple engineers replied "Phhht, yeah. You can't do it, but, yeah, if you could we'd use it."[2]

The StrongARM was a collaborative project between DEC and

Advanced RISC Machines to create a faster ARM microprocessor. The StrongARM was designed to address the upper end of the low-power embedded market, where users needed more performance than the ARM could deliver while being able to accept more external support. Targets were devices such as newer personal digital assistants and set-top boxes.[3][4]

Traditionally, the

. The project was set up in 1995, and quickly delivered their first design, the SA-110.

DEC agreed to sell StrongARM to Intel as part of a lawsuit settlement in 1997.[5] Intel used the StrongARM to replace their ailing line of RISC processors, the i860 and i960.

When the semiconductor division of DEC was sold to Intel, many engineers from the Palo Alto design group moved to

system-on-a-chip (SoC) products for the networking market. The Austin design group spun off to become Alchemy Semiconductor, another start-up company designing MIPS SoCs for the hand-held market. A new StrongARM core was developed by Intel and introduced in 2000 as the XScale.[6]

SA-110

The SA-110 was the first microprocessor in the StrongARM family. The first versions, operating at 100, 160, and 200 MHz, were announced on 5 February 1996.

Apple MessagePad 2000.[11] It was also used in a number of products including the Acorn Computers Risc PC and Eidos Optima video editing system. The SA-110's lead designers were Daniel W. Dobberpuhl, Gregory W. Hoeppner, Liam Madden, and Richard T. Witek.[3]

Description

The SA-110 had a simple

branch prediction
hardware, but had mechanisms for their speedy processing.

Execution starts at stage three. The hardware that operates during this stage is contained in the EBOX, which comprises the register file, arithmetic logic unit (ALU), barrel shifter, multiplier and condition code logic. The register file had three read ports and two write ports. The ALU and barrel shifter executed instructions in a single cycle. The multiplier is not pipelined and has a latency of multiple cycles.

The IMMU and DMMU are

pages
. The write buffer (WB) has eight 16-byte entries. It enables the pipelining of stores. The bus interface unit (BIU) provided the SA-110 with an external interface.

The PLL generates the internal clock signal from an external 3.68 MHz clock signal. It was not designed by DEC, but was contracted to the Centre Suisse d'Electronique et de Microtechnique (CSEM) located in Neuchâtel, Switzerland.

The instruction

set-associative
and virtually addressed. The SA-110 was designed to be used with slow (and therefore low-cost) memory and therefore the high set associativity allows a higher hit rate than competing designs, and the use of virtual addresses allows memory to be simultaneously cached and uncached. The caches are responsible for most of the transistor count and they take up half the die area.

The SA-110 contained 2.5 million transistors and is 7.8 mm by 6.4 mm large (49.92 mm2). It was fabricated by DEC in its proprietary CMOS-6 process at its Fab 6

thin quad flat pack
(TQFP).

SA-1100

The SA-1100 was a derivative of the SA-110 developed by DEC. Announced in 1997, the SA-1100 was targeted for portable applications such as PDAs and differs from the SA-110 by providing a number of features that are desirable for such applications. To accommodate these features, the data cache was reduced in size to 8 KB.

The extra features are integrated memory,

IrDA interface, a MCP, and a synchronous serial port
.

The SA-1100 had a companion chip, the SA-1101. It was introduced by Intel on 7 October 1998.

PS/2 ports, a USB controller and a PCMCIA controller that replaces that on the SA-1100. Design of the device started by DEC, but was only partially complete when acquired by Intel, who had to finish the design. It was fabricated at DEC's former Hudson, Massachusetts fabrication plant, which was also sold to Intel.[13]

The SA-1100 contained 2.5 million transistors and measured 8.24 mm by 9.12 mm (75.15 mm2). It was fabricated in a 0.35 μm CMOS process with three levels of

aluminium interconnect and was packaged in a 208-pin TQFP.[14]

One of the early recipients of this processor was-ill-fated Psion netBook and its more consumer oriented sibling Psion Series 7.

SA-1110

The SA-1110 was a derivative of the SA-110 developed by Intel. It was announced on 31 March 1999, positioned as an alternative to the SA-1100.

Jornada, the Sharp SL-5x00 Linux Based Platforms and the Simputer.[18]
It was also used to run the Intel Web Tablet, a tablet device that is considered potentially the first to introduce large screen, portable web browsing. Intel dropped the product just prior to launch in 2001.

SA-1500

The SA-1500 was a derivative of the SA-110 developed by DEC initially targeted for set-top boxes.[19][20] It was designed and manufactured in low volumes by DEC but was never put into production by Intel. The SA-1500 was available at 200 to 300 MHz. The SA-1500 featured an enhanced SA-110 core, an on-chip coprocessor called the Attached Media Processor (AMP), and an on-chip SDRAM and I/O bus controller. The SDRAM controller supported 100 MHz SDRAM, and the I/O controller implemented a 32-bit I/O bus that may run at frequencies up to 50 MHz for connecting to peripherals and the SA-1501 companion chip.

The AMP implemented a long-instruction-word instruction set containing instructions designed for multimedia, such as integer and floating-point multiply–accumulate operations and SIMD arithmetic. Each long-instruction word is 64 bits wide and specifies an arithmetic operation and a branch or a load/store. Instructions operate on operands from a 64-entry 36-bit register file, and on a set of control registers. The AMP communicates with the SA-110 core via an on-chip bus and it shares the data cache with the SA-110. The AMP contained an ALU with a shifter, a branch unit, a load/store unit, a multiply–accumulate unit, and a single-precision floating-point unit. The AMP supported user-defined instructions via a 512-entry writable control store.[21]

The SA-1501 companion chip provided additional video and audio processing capabilities and various I/O functions such as PS/2 ports, a parallel port, and interfaces for various peripherals.

The SA-1500 contains 3.3 million transistors and measures 60 mm2. It was fabricated in a 0.28 μm CMOS process. It used a 1.5 to 2.0 V internal power supply and 3.3 V I/O, consuming less than 0.5 W at 100 MHz and 2.5 W at 300 MHz. It was packaged in a 240-pin metal

plastic ball grid array
.

StrongARM latch

The StrongARM latch is an electronic latch circuit topology first[22][23] proposed by Toshiba engineers Tsuguo Kobayashi et al.[24] and got significant attention after being used in StrongARM microprocessors.[22][23] It is widely used as a sense amplifier, a comparator, or just a robust latch with high sensitivity.[22][23]

References

  1. ^ Levine, Daniel S. (11 August 2022) [1997-10-27]. "Intel, DEC Settle Alpha Chip Dispute". Wired.com. Archived from the original on 14 March 2016. Retrieved 11 August 2022.
  2. ^ Baum, Allen (18 July 2018). "Oral History of Allen Baum" (PDF) (Interview). Interviewed by David Brock. p. 60.
  3. ^ a b Montanaro, James et al. (1997). "A 160-MHz, 32-b, 0.5-W CMOS RISC Microprocessor" Archived 1 January 2019 at the Wayback Machine. Digital Technical Journal, vol. 9, no. 1. pp. 49–62.
  4. ^ "Digital targets supercharged StrongARM chip at consumer electronics market". PR Newswire. 5 February 1996. Retrieved 7 June 2011.
  5. CNet
    news.com. Retrieved 29 July 2008.
  6. ^ "Embedded Processor Watch #46; 5/4/1999". mdronline.com. Archived from the original on 19 October 2007.
  7. ^ Digital Equipment Corporation (5 February 1996). "Digital Targets Supercharged StrongARM Chip at Consumer Electronics Market". Press release.
  8. ^ Digital Equipment Corporation (12 September 1996). "Digital's StrongARM Chips Pull Away in Embedded Race". Press release.
  9. ^ Turley, Jim (27 January 1997). "Embedded Vendors Seek Differentiation". Microprocessor Report, pp. 16–21.
  10. ^ "Digital's StrongARM Microprocessors Take CPU Lead in Network Client Market". EE Times. 18 November 1996. Retrieved 16 March 2012.
  11. ^ Turley, Jim (18 November 1996). "Newton First Design Win for StrongARM". Microprocessor Report, p. 5.
  12. ^ Intel Corporation (7 October 1998). "Intel Introduces StrongARM Products for PC Companions". Press release.
  13. ^ "The Linley Group - The industry's leading experts in communications semiconductor markets". mdronline.com.
  14. ^ Stephany, R. et al. (1998). "A 200MHz 32b 0.5W CMOS RISC Microprocessor". ISSCC Digest of Technical Papers, pp. 238–239, 443.
  15. ^ Intel Corporation (31 March 1999). "Intel StrongARM Processor, Companion Chip Optimized For Handheld Computing Devices". Press release.
  16. ^ Martyn Williams (14 February 2003). "Intel puts StrongArm on death row". InfoWorld.
  17. ^ "The Linley Group - The industry's leading experts in communications semiconductor markets". mdronline.com.
  18. ^ "The Linley Group - The industry's leading experts in communications semiconductor markets". mdronline.com.
  19. ^ Rick Boyd-Merrit; Peter Clarke (24 July 1998). "Intel to reveal details on StrongARM chip". EE Times.
  20. Hot Chips 10
    .
  21. ^ Turley, Jim (8 December 1997). "StrongARM-1500 Grapples With MPEG-2" (PDF). Microprocessor Report. Retrieved 14 March 2024.
  22. ^
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    )
  23. ^
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    )
  24. S2CID 67412709.{{cite book}}: CS1 maint: numeric names: authors list (link
    )

Further reading