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The ARM computer was the invention of Acorn Computer Ltd. which was in 1982 the primary supplier of educational computers in the U.K. and produced the 6502 based BBC Micro. This product was similar to the Apple II in function and performance. Versions of this design were manufactured until 1993. The Acorn staff realized that there was a limit to the capability of the 6502 and searched for a replacement. For various reasons, some technical and others esthetic and ethnic, Acorn decided to develop their own 32 bit RISC processor using the outstanding talent provided by nearby Cambridge University. The first versions of the ARM were used as a co-processor on the BBC Micro, just as the CPM card had been used on the Apple II. The ARM operated through a small dual port memory and communication device called the TUBE. The operating system, user interface and other IO devices continued to be connected through the BBC main computer. It soon became apparent that the ARM tail was wagging the 6502 Dog. After Acorn was purchased by Olivetti (of Italy) in 1985 it became clear that a new ARM based computer would be needed to provide an upgrade or replace the BBC Micro. The companion chips MEMC - memory controller, IOC - IO controller and VIDC - Video controller were designed and the completed ARM based Archimedes was introduced in 1987. The software for the new computer was a direct outgrowth of the BBC. The operating system (called Arthur) preserved system calls, file system, and a Basic interpreter. This was similar to the IBM PC having a close resemblance to the preceding CPM machines. Much of the first Archimedes ROM was written in Basic! Since 1987 was post Macintosh, the original Archimedes also included the "Desk top" which provided a windowed user environment.
The evolution of the ARM proceeded in both hardware and software. The original ARM1 processor, built in 3 micron CMOS, operated at 6 Mhz. This was followed by the ARM2, built in 2 micron silicon, and available in versions capable of 12 Mhz operation. The ARM2 was used in the A310 Archimedes. It became apparent that the next version ARM would have greater performance if it could be integrated with an on chip cache, because it was capable of operating faster than available DRAMs. The ARM3 had 4 KBytes of cache built in and was fabricated out of 1.5 micron silicon in 1989. This processor had independent fast and memory clocks to decouple the processor and cache from the slow DRAM and IO. After several die shrinks the ARM3 now operates at 33 Mhz cache clock and still operates with the original MEMC, IOC, and VIDC, support chips. The initial Arthur operating system was followed by RISCOS. In RISCOS the built in ROM now contained a complete drawing package similar to display postscript and a more fully integrated window environment called WIMP (Windows, Icons, Menus, and Pointers). Acorn was even able to port Berkeley UNIX to the ARM3 powered A540. This port was called RISCIX and had the X-windows display system.
The new era in ARM was launched when the advanced development department within Acorn was spun off to form Advanced RISC Machines Ltd. (ARM Ltd.). The pressure to do this originated from the strategy to further the ARM marketplace by selling the parts to Apple and other real and potential competitors to Acorn. Ownership in ARM was split among Acorn, Apple, VLSI and the employees of ARM. The first project for the fledgling company was the ARM600 which was a new ARM6 32 bits core integrated with MMU, cache, write buffer and co-processor interface. This was quickly followed by the ARM610 which eliminated the co-processor interface in exchange for a lower price and smaller package. The ARM610 is currently encorporated into the Newton PDA and is supplied by 3 silicon vendors, VLSI, Plessy, and Sharp. The ARM60 without the built in cache and MMU was also built and encorporated into the 3DO interactive multiplayer.
The scene changes now to the efforts of the ARM licencees to find applications for the ARM6 (and now ARM7) core processors in all sorts of embedded applications. The small size and computing effeciency of the ARM core allows integration into entire computing systems on one chip. The 86C650 Laser Printer Controller is one such example and is now sampling.
1983 Work begins on ARM instruction set and architecture
4-1985 First samples of the ARM1 built by VLSI are working
1987 Archimedes is launched using ARM2 processor and chip set
1989 ARM3 processor with cache
1989 ARM2as Static ARM core
11-1990 ARM Ltd founded out of Acorn's advanced design division
7-1991 I join VLSI
10-1991 ARM600 samples delivered in 11 months
1992 ARM Ltd signs Plessy and Sharp as ARM licensees
1993 Apple launches Newton using ARM610
1993 3DO launches Interactive Multiplayer with ARM60
1-1994 VLSI produces 86C650 Microcontroller
7-1994 I write this article
ARM1 First Silicon 3u CMOS, 32 bit data and 26 bit address range
ARM2 Fabricated in 2 u CMOS, added multiply and multiply accumulate instructions
ARM3 1.5u to .6u ARM2 with cache and cache control logic
ARM2as 1.5u to 1u CMOS Static ARM core, added swap instruction
ARM6* 1u to .6u Embeddable Static CMOS core with 32 bit addresses, PSR registers added
ARM60* ARM6 with pad ring and JTAG
ARM600 ARM6 with 4K cache, MMU, Write buffer, co-proc. port and JTAG
ARM610* ARM6 with 4K cache, MMU, Write buffer, and JTAG
ARM700 ARM7 with 8K cache, MMU, Writebuffer, and JTAG, with co-proc port
ARM710* ARM7 with 8K cache, MMU, Writebuffer, and JTAG
ARM7500* ARM7 with 4K cache, MMU, Writebuffer, and JTAG
and every other PC peripheral.
ARM810^ ARM8 with 8K cache, MMU, Writebuffer, and JTAG (72Mhz)
SA110* SrongARM with 32K cache, MMU, Writebuffer, and JTAG (100 to 235Mhz)
* Currently in high volume production
^ Prototypes only
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