Re: Video Coprocessor
- To: Penio Penev <penev@xxxxxxx>
- Subject: Re: Video Coprocessor
- From: KC5TJA <kc5tja@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 10 Nov 1997 16:49:08 -0400
- cc: MISC
- In-Reply-To: <Pine.SGI.3.96.971110123125.27949P-100000@venezia.rockefeller.edu>
- Old-Date: Mon, 10 Nov 1997 13:44:34 -0800 (PST)
- ReSent-Date: Fri, 14 Nov 1997 14:23:55 -0500 (EST)
- ReSent-From: Penio Penev <penev@xxxxxxx>
- ReSent-Message-ID: <Pine.SGI.3.96.971114142355.18836a@venezia.rockefeller.edu>
- ReSent-To: MISC
>
> What is a "spurious black line" I have no idea, but I belive that this
> might happen.
A spurious black line occurs when the CPU has higher priority than the
video refresh hardware (however it may be implemented). This means the
video serializer register shifts all its pixels out before it can fetch
the next word of the video stream. In short, you get a small black line
in the middle of the video stream. Hence it's name... :) The earlier CGA
and EGA hardware for the PCs also exhibited this problem. This was fixed
in later generations of the EGA. Fortunately, VGA never had the problem
to begin with.
> > (the old TRS-80s
> > had this problem).
>
> I'm quite sure the old TSR-80s does not use MuP21 :-)
No, they used a Zilog Z-80A. Model I used a clock speed of 1MHz, Models
II and III (I think) used a 2MHz clock speed, and a TRS-80 Model IV used
4MHz Z-80B.
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