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Widget images and boot blocks

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paule:
Now that I have imaged my XENIX widget, will restoring that image also restore the XENIX boot-ability if I have switched OS's to another in the mean time? E.g. if I install LOS on that drive will I later be able to restore back to XENIX or will I need to reformat the drive with the XENIX installer first? Are there any other pitfalls in switching OS's on the Widget?

sigma7:

--- Quote from: paule on February 21, 2023, 03:39:27 am ---Now that I have imaged my XENIX widget, will restoring that image also restore the XENIX boot-ability if I have switched OS's to another in the mean time? E.g. if I install LOS on that drive will I later be able to restore back to XENIX or will I need to reformat the drive with the XENIX installer first? Are there any other pitfalls in switching OS's on the Widget?

--- End quote ---

Restoring the image will bring it back to the same state.

More than you wanted to know:

BLU (and probably any other similar tools that are not running within a normal Lisa operating environment) access the drives at the hardware level, being mostly(*) agnostic as to what is at whichever sector (similar to dd), and bypassing any Lisa drivers that might reveal only a partition when run in an OS. eg. if you have a Widget set up as a dual LOS/MacWorks disk, BLU will be saving/restoring the combination. Wheras a utility running in MacWorks (eg. FEdit) would only see the MacWorks portion of the disk.
If you have an IDEfile or X/ProFile, then the single medium connected to it may have multiple drive images, but only one is active at a time. In this case BLU would be saving/restoring only the currently operating drive image. Moving the medium (eg. CompactFlash card) from the parallel port drive emulator to eg. a card reader on a modern computer would permit accessing all the images at the same time. Depending on the device, the images may show up as separate files in a partition/directory (as with the FloppyEMU, and the IDEfile IIRC, and ...), or be invisible on a separate partition (but still accessible using dd, eg. as the X/ProFile media is formatted).
There are potential hiccups if you are attempting to move an image from a ProFile to a Widget or vice-versa. The ProFile is interleaved by the driver, while the Widget is not (Widget interleaving is applied to the disk itself when low-level formatting). In addition, for a ProFile, the tags come before the data, and for a Widget the tags come after the data.

(*) When BLU images a ProFile, it de-interleaves so that consecutive sectors in the image correspond to consecutive sectors at the OS level. This is unnatural compared to direct access of the hardware interface, but the result is that the sectors in the image are in order for things like disassembly and hex editing. The sector data order in the image is thus more or less the same as a Widget with the same data (eg. LOS) on it. BLU also arranges the tags for the Widget and ProFile in the images so the tag/data order is the same. This was to facilitate moving an image between a ProFile and a Widget with BLU, but beware that boot blocks are different for the two devices (and sometimes different depending on the port) so the moved image may not be bootable or may not work at all depending on the operating environment. Whenever possible, it is preferable to restore an image to the same type of device (ProFile/Widget/Priam) that it was saved from.

compu_85:

--- Quote from: sigma7 on February 21, 2023, 05:14:32 am ---...There are potential hiccups if you are attempting to move an image from a ProFile to a Widget or vice-versa.

--- End quote ---

Ah, I wondered why this gave trouble. Thanks for the explanation!

paule:
That's all really helpful information and a nice recap. There's never more than I want to know  :D

That helps me to feel comfortable in trying to install LOS on this system (which has only had XENIX since I got it).

Is there a certain minimum LOS required for installing on a Lisa 2/10 (H/88 ROMs)? And Workshop and Monitor versions?

sigma7:

--- Quote from: paule on February 21, 2023, 02:28:57 pm ---Is there a certain minimum LOS required for installing on a Lisa 2/10 (H/88 ROMs)? And Workshop and Monitor versions?

--- End quote ---

As far as I know:
- all Lisa software that was available on 3.5" floppies will work on the 2/10 with I/O ROM 88 (*)
- CPU ROM version H is backwards compatible with all the software before it. (**)

(*) Xenix makes an assumption about the hard disk size depending on the I/O ROM version, see Note 2 in Modifications to Lisa Xenix 3.0 to make it more compatible with the X/ProFile

(**) There was/is a rumour that you need an earlier version ("D" I think) to use Twiggies in some cases, but I don't recall if there is proof of that.

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