On 2015-09-21 17:03, Paul Koning wrote:
On Sep 21, 2015, at 10:52 AM, Johnny Billquist <b...@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.
You are absolutely right.
And I don't know the actual size of the boot blocks. It might very well
be that they both fits in the same boot block, which would be nice.
I know that the M9312 have separate boot roms for the RX11 and the
RX211, but those boot roms are pretty tiny...
And I don't know if the RX211 boot rom also deals with RX01 floppies,
but I would assume it does.
Johnny
