[Simh] SIMH Development

[Stephen Hoffman]

> In case anyone is interested I am adding a differencing disk feature that
> allows you to store only the changes to a virtual disk file, so you can
> rollback to a known state, or keep the differences from a base image in a
> smaller file, like undo disks in Virtual PC.

So that I might understand this, what you're offering here is analogous to an (off-line) diffutils (diff and patch, et al) for Windows and that's tailored for big wads of disk data?   

Or is this differencing mechanism implemented at run-time from some known checkpoint where the data is consistent, where you're running some sort of tracing and checkpointing akin to what OpenVMS host-based shadowing and its minicopy or minimerge provides?

FWIW, with OpenVMS VAX, it's feasible to do this sort of known-starting-state task using a known install image and a real or host-based InfoServer disk service.
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