RE: commdore screen text / graphic mode

Date: Thu, 15 Nov 2012 20:38:40 +0100
Message-ID: <000901cdc368$d167ac60$74370520$@org>
Thanks all, this is very interesting


I can now complete my emulation of the cbm 4000/8000 screen on a propeller


Btw:  If someone is interested, I have a set of French eprom using the “commodore” keyboard (derived from the German Keyboard)

           Before the French keyboard was produced by Commodore we had our own set called internally as “Procep Keyboard”


Eprom set for the French version of the commodore 8000

Edit : $e000.bin 


Edex $a000.bin   (basic extension added to all commodore 8XXX sold in France





De : [] De la part de A.Fachat
Envoyé : jeudi 15 novembre 2012 06:32
À :
Objet : Re: commdore screen text / graphic mode


You might look at my analysis of the pet crtc stuff here
There also is a more generic page on the crtc on my site. 

The number of rasterlines is indeed the register value mentioned plus 1.


Rob Clarke < <>> schrieb:

I did a bit of analysis on this last year when I was working out the 
refresh rates on various CRTC PET's. I looked at all the edit roms on 
zimmers and put all the CRTC initialisation registers into a s/sheet. 
You can get it here:

THere's two rows for each ROM, being the initialisation registers for 
text and graphics modes respectively. As Martin said, it's usually 2 
except for one alternate version of the 901474-04 rom which had only 1 
extra scan line.


On 14/11/2012 23:11, wrote:

Apparently on the commodre 8000 the fo
displayed is 8x8 but apparently some blank lines can be added in “text” mode

Do you have any idea on the exact number ?

The data in the register of the 6545 is 9 in text mode and 7 in graphic mode…

Is there 1 or 2 blank lines ?

I don’t remember very well….




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