Before university Sophie designed and built systems counting translucent drops of liquid and detecting spun fibre machinery breakdowns; in her first vacation she developed a cow-feeder. She designed the Acorn System 1, coding the operating system in binary before designing and implementing Acorn Assembler, Acorn MOS and BASIC.

She and Steve Furber took less than a week to design and implement the prototype of the BBC Microcomputer, winning Acorn the contract for the Computer Literacy Project. Sophie designed the operating system and designed and implemented BBC BASIC for a succession of processors.

She and Furber co-designed the ARM processor powering Acorn's computers during the 1990s and virtually every mobile phone and tablet in the world nowadays – 200 billion sales of ARM powered chips to date (July 2022). She co-designed the ARM3, ARM610 and ARM 700 processors and ARM7500FE single chip computer. She created Acorn Replay multimedia software.

By 1999, Sophie developed the Firepath SIMD LIW processor and she and six others founded Element 14 to exploit this for ADSL. Sophie led the design of the instruction set for Firepath, wrote the Architecture Guide and led the SoC designs. Broadcom bought Element 14 at the end of 2000 and went on to win the majority of the Central Office DSL business. Sophie continues to develop the Firepath processor.

Sophie is a Broadcom Fellow and Distinguished Engineer, a Fellow of the Royal Society, a Fellow of the Royal Academy of Engineering, a Distinguished Fellow of the British Computer Society, a Fellow of the Women’s Engineering Society, an honorary Fellow of Selwyn College, Cambridge, an honorary Fellow of the Institution of Engineering and Technology (IET) and an honorary Fellow of the Institution of Engineering Designers (HonFIED). She has an honorary doctorate of science from Cambridge University and a CBE.