Also wrote the BBC BASIC ROMs used on Acorn computers in 6502, and later BBC BASIC V (five) in ARM. (ARM originally stood for Acorn RISC Machine.) Being able to successfully run the 6502 BASIC ROM is considered a test of how good a 6502 emulator is; his 16KiB of machine code, generated from hand-written assembler, used every trick of the CPU to squeeze in the code. This meant that when the BBC Master 128 came along, with its slightly later 6502 deriative, he could re-write some of it to use the new op-codes, taking less space, and thereby getting in a few more BASIC commands.
Also wrote the BBC BASIC ROMs used on Acorn computers in 6502, and later BBC BASIC V (five) in ARM. (ARM originally stood for Acorn RISC Machine.) Being able to successfully run the 6502 BASIC ROM is considered a test of how good a 6502 emulator is; his 16KiB of machine code, generated from hand-written assembler, used every trick of the CPU to squeeze in the code. This meant that when the BBC Master 128 came along, with its slightly later 6502 deriative, he could re-write some of it to use the new op-codes, taking less space, and thereby getting in a few more BASIC commands.