From iss I've learnt the fundamentals necessary to support 8DOS v1:
- the boot ROM is visible from $320 to the end of that page; and
- the Disk II controller registers are exposed from $310.
Since iss' post refers to the DOS 3.3 layout, one can deduce that the interface uses the 16-sector state machine P6 ROM and that the boot ROM is an exact analogue of Apple's 16-sector boot ROM. Apple's ROM (commented disassembly) is fully relocatable but is also 251 bytes of code and loads its boot sector into a different location — 0x800 on the Apple versus 0xb800 with the Pravetz — so Pravetz's is not a direct copy of that.
The Disk II and Apple DOS 3.3 are very well documented elsewhere; see Beneath Apple DOS, Beneath Apple Prodos (which has a fully explanation of the controller in addition to being about a different operating system), Inside the Apple IIe, etc. All available on archive.org.
The original version of 8DOS uses regular RAM for its workspace. Version 2 onwards use overlay RAM.
So, the dangling question:
- where and how does the Pravetz disk interface provide a control for ROM paging?