Re: broken double hires

[ralphp@gcstation.net (Ralph Wade Phillips)]

Hi, Louis!

In article <52keot$fia@news.gate.net>, louiss@gate.net              (Louis
Schulman) wrote:

> In <52c8mk$r4$1@mhadf.production.compuserve.com>, 100041.1464
<100041.1464@CompuServe.COM> writes:
> >Which parts of my Platinum //e are responsible for the double 
> >hires graphics?
> >It's not working anymore. Yesterday (maybe last month) double 
> >hires was running fine, now the screen is missing the half of the 
> >pixels.
> >The orig. (small) Apple 80 col/64KB card is ok, I tested it with 
> >another _simple_ //e.
> >Are there chips in the Platinum to change and so repair the double 
> >hires. I think everything else is working fine.
> >
> >Stephan
> 
> There seems to be something missing from your question.  I assume you are
> using some video card?  At least on my //e, the standard 80 col card and video
> port don't give you double hi-res, you need a video card.

        (cough)  On the REV"B", otherwise ORIGINAL, //e, all it took for
Double HiRes was a) a video board with 64K on it, and b) the DHR jumper
installed.  On the REV"A" board, the DHR jumper just locked the computer
up (had to do with a minor replumbing of Slot 7 ... ).  To quit, either a)
the 64K card is bad, b) the JUMPER is missing, or c) the CONNECTOR is bad.
With a chance that d) the PAL is bad, but this is a rather UNIQUE failure
mode ... <B-)

        No video "card" needed.

> 
> Given that, have you tested the video card?  What kind of monitor are
you using?
> Have you tested that?
> 
> To directly answer your question, double hi-res is firmware that resides
in the 
> video rom.  That does not seem to be a likely cause of this kind of problem.

        Nope, no firmware.  Just a minor rewiring to enable the extra
softswitch to bank in/out the alternate HiRes video screen (the one on the
64K memory expansion, that is.)

> 
> What do you see?  When you say the pixels are missing, are they blank? 
Do they
> work in other modes?
> 
> Interesting problem, though.
> 
> Louis

        RwP

-- 
Ralph Wade Phillips, CET #LA-82
ralphp@gcstation.net