mdj wrote:
> On Nov 13, 10:19 am, "Michael J. Mahon"  wrote:
>> Michael J. Mahon wrote:
>>> Bill Garber wrote:
>>>> "Jerry"  wrote in message
>>>> news:m363mt5zna.fsf{at}yahoo.ca...
>>>>> mojoehand  writes:
>>>>>> Jerry Penner, I wanted to thank you for the
information you emailed,
>>>>>> but my reply bounced. It seems that Yahoo is being
too agressive in
>>>>>> its spam filtering.
>>>>> Must be.  There was no message in my spam folder at
all, which is the
>>>>> usual case.
>>>>> I would have put the patent document online, but I don't have a
>>>>> web-site right now.
>>>>> For others who are interested, the patent is US#
4,631,692, and can be
>>>>> found at uspto.gov.
>>>> I went there, and searched it, and the only info available
was that it
>>>> had expired on December 23, 1998. I couldn't actually find
the Patent
>>>> there.
>>> Go to:  http://patft.uspto.gov/
>>> and select Patent Number Search, then enter 4631692 and you'll see
>>> the patent.  It describes a 4-bit shift register implementation,
>>> where the shift register is clocked at 14.3MHz--the classic 16-color
>>> implementation.
>> I see Jerry made an equivalent suggestion.  ;-)
>>
>>  From the patent description, it seems that AN3 and /80COL need to be
>> made available to the card to do mode selection.  (I wonder why the
>> /DEVSEL space wasn't used for this function?)
> 
> The 80COL and AN3 softswitches are used in the IIe to enable Double
> Hires and Lores modes. The Video7 RGB adapters established a protocol
> for toggling these switches in certain sequences which enable
> selection between DHR colour, mono, mixed, and '160' modes. There's
> also a FG/BG mode that lets you do 280x192 single hires, and the AUX
> page holds the FG/BG colours for each screen byte.
> 
> Using the protocol allows software to 'support' RGB cards by selecting
> whatever mode is appropriate with completely benign results on non-RGB
> equipped Apple II's.

Ah, yes--"backward compatibility" for the new software, and simpler
than providing a scheme for software to detect the card's presence
(or absence).  Just what I would have done in the circumstance.  ;-)

-michael

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