Anyone have an image of a Japanese PET chrgen ROM 901447-12?

Ethan Dicks ethan.dicks at
Mon Apr 5 17:18:33 CDT 2010

On 4/5/10, M H Stein <dm561 at> wrote:
> ----------------Original Message:
> Date: Mon, 5 Apr 2010 02:13:20 -0400
> From: Ethan Dicks <ethan.dicks at>
> Subject: Anyone have an image of a Japanese PET chrgen ROM 901447-12?

> It would certainly be nice to find the 'official' ROM, but I thought that
> the ROM that Philip (the owner of that PET on your bench) created
> was pretty well complete and correct; it seems to match my Japanese
> keyboard perfectly except for one character, and I suspect it's the key
> that's wrong and not the CG.

Why would the key be wrong?

> Did you try that image and match it up to your Japanese chiclet
> keyboard?

I have not.  If you could send me a copy of it off-list, that would be
appreciated.  I don't seem to have it in the place I store such things
(though I do remember the conversation).

> I've been playing with the idea of having all three (four?) character sets
> available on screen at the same time, using the reverse video signal.

How would that work?  Obviously, you'd use some new means of toggling
upper bits on the CHRGEN ROM, but I don't get how the reverse video
signal would be the trigger... the upper bit on a PET character cell
inverts the data out of the bit shifter (unlike the C-64 where it's
just another address bit).  I can see how you could steal that upper
bit and pipe it into A11 on a larger CHRGEN ROM, but how do you get 3
or 4 sets from one bit?


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