I'd assume he means ZXAM which, while not totally accurate, it was about 90-95% compatible to 48k software and it emulated the AY sound chip as well.
Compatible as in 'it loads and runs' or 'it actually looks and sounds like it's supposed to'?

If it's the former then I can believe the 90-95%, but if it's the latter then not.
EDIT: a small clarification: 'it actually looks and sounds like it's supposed to while running at full speed and 50fps on an 14MHz A1200'
