BBC Model B - video help

From: Allison J Parent <>
Date: Mon Feb 16 21:46:02 1998

<the only thing that could cause this would be the 6845 CRTC chip (IC2 on
<my schematic). The cursor signal is produced by that chip (at least in

Unlikely but possible. More likely is a memory address error. A stuck
address line will cause data to repeat 2*n times in the display memory.

<modes 0-6), and so if there was any problem later on, then at least the
<cursor would be in the right _phyical_ position, (and would presumably
<not line up with what you are typing). If the 6845 is socketed, then try
<reseating it (pull it out and push it back in again).

Same for other chips around it.

Received on Mon Feb 16 1998 - 21:46:02 GMT

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