21 Sep
2015
21 Sep
'15
8:03 a.m.
On Sep 21, 2015, at 10:52 AM, Johnny Billquist <bqt
at Update.UU.SE> wrote:
...
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
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.