“The ARM Architecture – From Sunk to Success”
Dave Jaggar – former ARM’s Head of Architecture Design, New Zealand
In the late 1980’s Acorn, a British one-hit-wonder computer company, developed its own workstation microprocessor, the Acorn RISC Machine (ARM). By the end of 1990 Acorn was down a very dark financial alley, and the ARM processor, which may well have been the worst microprocessor ever designed, was practically extinct. Acorn’s VLSI design team, minus the two original CPU designers, were cast out to fend for themselves, provisioned with only 18 months of financial rations from Apple. When Dave Jaggar joined the new company in the summer of 1991, with the ink not quite dry on his Master’s thesis, he thought perhaps it was the worst move since Martin Luther journeyed to Rome. However after twelve months he was given free rein to redefine the processor, mostly because the company couldn’t afford anyone better. The Advanced RISC Machine, as the company was renamed, had a completely new instruction set which sidestepped many of the problems inherited from the original. Over the next eight years Dave systematically defined the entire ARM architecture, enabling it to be a popular embedded controller for the digital revolution, with around 100 billion units shipped. Along the way he worked out a little bit about computer architecture, and then retired back to New Zealand to work out a bit more. Now that ARM is no longer independent, and Britain is about to be, Dave thinks it’s about time he explained his part in ARM’s downfall
Dave Jaggar was ARM’s Head of Architecture Design in Cambridge, UK. During Dave’s nine years at ARM he took a British processor architecture, gave it a 2nd integer instruction set which made it excellent for embedded control, added on chip debug so it could be buried in a SoC, gave it a new floating point instruction set, and rebuilt the system architecture so it could run Unix like OSes properly. He is the Founding Director of the ARM Austin Design Center in Texas -where about half of the A series chips for phones are done and authored ARM Architectural Reference Manual. Dave is now retired in Christchurch, New Zealand.
Oral History interview – Mountain View, California, 2012