TRS-80 software I wrote
Your donation gives me time
This package contains programs which work directly with diskettes.
My disk subsystem was initially a standard single-density System-80 one. I guess this meant it was memory-mapped just like the TRS-80 one. For once Dick Smith decided against a trivial hardware change which ruined compatibility with the TRS-80 Model 1 ... so thankfully all OSs and disk-using programs written for the Model 1 worked fine on the System-80.
I tried to get Double Density by adding a suitable controller. The original controller was the Western Digital WD-1771. I tried adding the WD-1790 (I think that was its designation) which is supposed to be able to do Double Density, at the expense of not being able to handle 2 of the 4 Data Address Marks which the 1771 could make.
After some trouble getting my hardware and software working I had single density working with the WD-1790, but double density just didn't work somehow. So I bit the bullet and bought a "commercial" Double Density adapter board made by Errol Rosser (see http://www.cia.com.au/rcsradio/sydtrug.htm). Errol's board required the original Single Density controller to plug into a socket on the board. It then switched between controllers, using the Double Density controller only for Double Density work. This preserved compatibility with the 4 Data Address Marks.
Oh yes, the programs ... I have no idea what most of them do. The code looks like a lot of them were written around the same time.