Multi-platform distribution format (Was: Backups [was

[Paul Koning]

> On Sep 21, 2015, at 10:52 AM, Johnny Billquist <bqt at Update.UU.SE> wrote:
> 
> ...
>>> I've tried to boot an RX01 Floppy in RX02 mode, that failed on all disks
>>> I've tried. Is an original RX02 able to boot (RT11) from an RX01 disk?
>> 
>> As far as I know, it can't. An RX02 can read/write an RX01 disk, but the software
>> interface to the controller is so different (the RX)2 uses DMA, the RX01 doesn't for
>> one thing) that the RX02 cannot boot an RX01 disk.
> 
> Of course an RX02 *drive* can read an RX01 *floppy*. And yes, a system with an RX211 and an RX02 *drive* can boot from a floppy that what written by an RX01 *drive*. But you need the boot code for an RX211 controller, and that boot code also needs to handle RX01 format floppies. If the boot sector on the floppy is for an RX11, then no, an RX211 will not understand things. The programming model for the two controllers are different. You need different device drivers.
> 
> But this is really a question about the controller and the software running it, not the floppy or the drive.

And it would certainly be possible to write a driver that can handle both controllers; it would start by determining which controller it's dealing with, and then run the one or the other set of algorithms.  Since a boot block is just a small driver, the same is true there, so long as the whole body of code fits in the available space.  I suspect in this case that's doable; most bootloaders (other than MSCP ones) require only a small fraction of the available space.

	paul