I did something similar in the early nineties by using the venerable AM7910, an old modem chip often used in vintage computer and Ham Radio gear, to make an int

I did something similar in the early nineties by using the venerable AM7910, an old modem chip often used in vintage computer and Ham Radio gear, to make an interface to store and retrieve data on tape from my Amiga 500. I used a normal cassette deck for storing, but the chip was really slow at 1200 bps, even for an old system like AmigaOS, and per data sheet it didn't offer higher speeds, however I tried anyway to change its clock frequency by testing a few Xtals in place of its 2.4576 MHz standard one, and eventually settled to an old PAL color TV Xtal (4.433619 MHz) that would nearly double the speed without introducing errors. Good old times...