Re: PET 2001 Fix....WAS: Will pay good money for NON working PET 2001 motherboard.

From: Marko Mäkelä <>
Date: Wed, 25 Nov 2009 11:49:44 +0200
Message-ID: <20091125094944.GA22929@x60s>
Hi Philip,

On Wed, Nov 25, 2009 at 09:48:37AM +0900, Philip Lord wrote:
> Thanks for the reply Marko,
> Having never actually used a Commodore computer before (yes it's true. I 
> was a Sinclair guy growing up. Sorry)

I can forgive you.  I hope that everyone can forgive me that I am almost
a Sinclair guy too (using GNU/Linux on x86 and x86-64, which are remotely
similar to the Z80). :-)  I started with the C64, then got a PC (with
MS-DOS and Windows 3 in 1991, with GNU/Linux since 1993) and collected
quite a few machines since then.  Last summer, I gave away all but the
C64, VIC-20 and C128, and I have to confess that I haven't touched those
either.  Family and other hobbies are consuming my time.

It has been a while since I read the Usenet, but is the annual
comp.sys.sinclair+comp.sys.cbm flame war still going on? :-)

> Anyway, just as a confirmation...are you suggesting in the second  
> character set, that I should replace the uppercase glyphs with the  
> Japanese, and then replace the the lowercase with uppercase?

I was suggesting that you copy the uppercase/graphics set to both halves
of the ROM and replace the graphics glyphs in one half with the Japanese

An easier alternative might be that you take the VIC-1001 character ROM
and remove the inverted letters.  (I think that the PET does reverse
graphics in hardware.)  That is, copy the first 1024 bytes, skip the
next 1024 bytes, copy the next 1024 bytes (and skip the last 1024 bytes).
1024 = 128 glyphs*8 bytes per glyph.  The high-order bit of the
character code indicates inverted graphics.  The VIC-20 character ROM is
4096 bytes, while the PET character ROM should be 2048 bytes.


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Received on 2009-11-25 10:00:04

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