Acorn BBC Master Turbo

The Master Turbo is a Master 128 with a Master Turbo Module installed. I am not sure if the Turbo Modules were factory installed and sold as Master Turbos, or dealer/customer installed. However the price lists for 1986 only list the Master 128 and the Turbo Module (£125). The Master Turbo Module had a faster CPU (4MHz instead of 2MHz) and almost 64KB of usable memory which gave approximately 50% performance improvement over the Master 128. It ran the host operating system in the same way the earlier BBC Mirco 6502 second processors did.