[Coco] [!! SPAM] Re: [!! SPAM] Re: Coco compatible monitors...

[gene heskett]

On Saturday, July 02, 2011 10:20:49 AM John Kent did opine:

> On 2/07/2011 3:22 PM, gene heskett wrote:
> > It is not interlaced John.
> > 
> > Cheers, gene
> 
> Hi Gene,
> 
> In that case you just need a line buffer, or actually 2 to ping pong.
> It would work as a line doubler which would make it a bit simpler.
> Ideally you'd want a PLL to lock onto the pixel stream so that you could
> sample synchronously with the pixels or else clock the scan line
> converter with the VDG clock. Ideally the timing would be adaptive but
> if the scan converter was designed for the VDG the timing is fixed so it
> wouldn't have to be adaptive.
> A friend from the Flex users group was looking for a scan rate converter
> for his old Flex / UniFlex machine and showed me the link I posted. I'm
> not sure if he bought one.

I think that is the general idea Roy's device uses, along with a couple of 
pots to scale the a/d response to the machine.  It is quite usable, with 
some reservations about the blue because the tendency to set the pots to 
reduce the digital background noise also takes away some of the gain, and 
since the blue is the least amplitude, it suffers.  I think this may be a 
characteristic of my gime also, and if some way to enhance the gimes rise 
and fall times could be found, that would alleviate much of the problem.

Unforch, the output stages in the gime were apparently on a power budget.  
Mine has rise & fall times in the 400ns range.  Since the cm8 was also 
severely limited, so severely that trading it for a Maggy 515 was a huge 
improvement, but even that never made a blue 80 column text screen 
readable.

I have no clue if raising the VCC on the gime would help, never tried it, 
basically because if you push the envelope and blow the gime, there aren't 
any replacements other than raiding another coco3. It might be amazing what 
6 volts on the VCC pin might do for it.

I have even considered sampling the memory signals and making my own set of 
2 bit d/a's to replace the gime's anemic output stages, but I need to make 
some round tuits first as I have people clamoring for them.  Still looking 
for suitable artwork for (preferably 2 difference faces so there is a heads 
and a tails sides) that.  What I have found on the net is either way too 
complex to try to put on a 50 cent sized coin due to the carving time 
involved (a whole page of text), or best described as ugly.  Graphics files 
for something attractive gratefully accepted.

> John.


Cheers, gene
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Nice guys finish last.
		-- Leo Durocher