Re: "Commodore 64 Prototype Project"

On Monday 07 May 2012, you wrote:
> Hi,
> 
> On 2012-05-07 15:42, Per Olofsson wrote:
> > You can find more images of a previously sold unit here:
> >    http://jpegbay.com/gallery/001326274-5.html
> > 
> > Looks like a devkit to me, with RS-232 ports for uploading ROM images.
> 
> I agree.
> 
> The theory that is it a RAM-based cartridge devkit/system suited for
> game development is backed up by the fact that they did a lot of work
> exposing the *both* joystick ports and keyboard on the front plate.
> 
> It seems a little unlogical to expose especially the joystick ports if
> it was a "just" RS-232 communications server...
> 
> 
> It appears to me that the system never has had any proper back-plate.
> This means that all ports of the C64 and the prototype board was exposed
> on the back.
> 
> The Textool ZIF-socket on the prototype board seems to have had an
> important function as it is directly accessible on the back of the system.
> Something that indicates that it is to be used frequently.
> 
> http://jpegbay.com/gallery/001326274-15.html#15
> 
>  From the location of the Textool ZIF-socket another theory could be
> that the system is a EPROM burner ? then but why have joyports exposed
> on the front ?
> 
> Another thing that puzzles me is - if it is a devkit - why two serial
> ports - why not only one ? If the second serial port was "for free" I
> could understand - but it seems that the constructor deliberately have
> designed it with two ports.
> 
> 
> Can anyone come up with a theory about the second switch on the front
> plate ? it is soldered to the board here:
> 
> http://jpegbay.com/gallery/001326274-7.html#7
> 
> The first switch is the power switch.
> As for the second front switch the soldering location near to U20
> (NE556) could indicate that it has something to do with NMI - maybe a
> substitution for a Restore button ? That would indicate that another
> type of external keyboard was used - only that it would have to have the
> same kind of keyboard matrix... hmm ???

it could also be some kind of debug setup.... a simple sort of "in circuit 
emulator" .... then pulling nmi would start a "monitor rom" for debugging ... 
eventually using rs232 for interfacing with some other computer.



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