Re: Feasibility? - 1541 Ultimate conop

Re: Feasibility? - 1541 Ultimate conop

From: Justin <>
Date: Thu, 13 Aug 2009 22:24:21 -0400
Message-Id: <>
While I agree that it would be a lot of work, the existing freezer is  
essentially doing a DMA swap every time you operate it.  It is not  
perfectly reliable but it does work the majority of the time and will  
likely be better with the 1.7 firmware.  In terms of the delta in load  
times, I think it would be far more dramatic.  For example, I was  
doing some benchmarking on my SX-64 after installing JiffyDOS, and the  
load times from a real floppy for SkyFox to get to its initial screen  
were several minutes, enabling JiffyDOS makes it noticeably faster,  
but the load time is still measured in minutes.   DMA would be a  
couple orders of magnitude faster.

I also think that aside from the idea of a RAM snapshot, extending the  
image format so that diffs are calculated against it, allowing it to  
be reverted, makes sense as a separate feature.  It would make image  
management much more convenient, for example when building out a set  
of GEOS disk images or the like.  Just hitting revert from the freezer  
menu would be fantastic.

On Aug 13, 2009, at 1:15 AM, Groepaz wrote:

> On Donnerstag 13 August 2009, Justin wrote:
>> 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?
> sounds very pointless to me. it's a lot of work (and i mean it, a  
> LOT) to get
> it right (not even the existing freezer works right) and all that to  
> speed up
> initial loading times that arent more than 5 seconds or so with a  
> cartridge
> anyway.
> -- 
> Vor tausend Jahren hätten die Höflinge es gemerkt, wenn der König oder
> Herrscher unmerklich verrückt geworden wäre. Heute würde es ihnen  
> garnicht
> auffallen.
> <Sir Peter Ustinov>
>       Message was sent through the cbm-hackers mailing list

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Received on 2009-08-14 11:32:23

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