I posted this on the 1541U forum but that is a pretty limited group  
and most people there are not as intimate with the hardware as I see  
on CBM hackers, so I thought I'd chuck this idea out there to see  
whether it made sense.  I'll likely float it elsewhere as well.

I have an idea that I think the 1541U would be a very "ultimate"  
feature.

We all know that the wonderful thing about the 1541U is the  
combination of excellent emulation of the real hardware along with the  
ability to use the freezer to change images on the fly. The 1541U also  
handles .T64 files and will do the fast DMA injection and execution of  
those programs. The DMA approach won't work for conventional D64 or  
G64 images, but what if the image format is extended to include a  
snapshot of RAM at the moment when the program finishes loading to its  
main screen? This would be akin to the suspended state in a VMWARE  
image. Then you could select the image file, the 1541U would DMA the  
snapshot into RAM, load the image file into the emulated 1541, and  
then resume execution.  I would imagine that to really do this right,  
you'd also want to preserve a snapshot of the original image, and keep  
any writes to it (from a program that writes back to the disk) as  
diff's from the original image.  That way at any time you could revert  
the image, redo the DMA load of the memory snapshot, and start over.   
I don't really imagine this creating significantly larger file sizes,  
and the usability improvements would be exceptional.  Things like  
JiffyDOS would be more or less obsoleted by this approach except for  
in-image alteration.  And frankly there is no reason that cannot be  
done inside the 1541U's freezer menu beyond someone taking the time to  
write it.

Comments?

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