22-05-2020, 10:52 PM
(13-05-2020, 05:56 PM)IanMcLean Wrote: ..... The instructions for performing the upgrade in the Microbee Technical Manual are a fairly poor scan quality. I am not sure I want to do this based on these scans. Is there a better more hi-res scan of this anywhere?What is the actual document name and can you give me a page number ? I assume you got it from the Repository here ? I can always scan my original copy.
Also, from The Catcher v2_03
MOD TO CHANGE CLOCK TO 3.375 MHz.
(Required for 80 x24 char format. Factory fitted to IC Bees).
1. Remove the 12MHz crystal and replace it with a 13.5 MHz crystal.
2. Remove IC32 or cut pin 8 of+ and remove. (0/P of divide by 6 chip clock signal to CPU, PIO etc).
3. Connect track where IC32 pin 8 was to IC30 pin 10 (Divide by 4 0/P) of IC26 74LS161.
4. This mod gives 13.5 / 4 = 3.375 MHz main clock instead of the old 12 / 6 = 2MHz signal. It also gives 13.5 MHz instead of 12 MHz to IC12 and a
1.4 MHz char clock to the 6545 instead of the previous 1.25 MHz. This clocks out the characters faster, allowing 80 to fit across the screen.
5. Install new basic 5.22e.
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ChickenMan
ChickenMan
