Re: PET 50Hz editor ROMS

Hi William,

I collected all the CRTC values from known ROM's into a spreadsheet, you 
can find it here.

http://inchocks.co.uk/commodore/PET/PET_CRTC.xls

The one in the first column is row 8 on the sheet, which also gives you 
a 50hz display but as you say, with slightly adjusted geometry.

Rob

On 26/04/2014 07:13, William Levak wrote:
>
> On zimmers.net under PET firmware there 3 separate images for the 
> 901474-04 50Hz screen editor ROM. I have compared them and found only 
> a few differences.  The affected region is listed below.  The three 
> columns below are the three different ROMs in the same order they are 
> listed on zimmers.net.
>
> $E787 is the ROM checksum.
>
> The other data almost looks like random garbage, but it has a 
> pattern.  It took me a while to remember where I had seen that 
> pattern.  They are the register values for the CRTC.
>
> According to my CRTC notes, the last column is values for an external 
> PAL monitor.  The middle column is values for a 50 Hz internal monitor.
> I don't recognize the values in the first column.  They are almost 
> like the 60 Hz internal monitor, but the vertical spacing is different.
>
>
> E72A:  31  32  3F
> E72B:  28  28  28
> E72C:  29  28  32
> E72D:  0F  08  08
> E72E:  27  26  20
> E72F:  00  02  10
> E730:  19  19  19
> E731:  20  20  1D
> E732:  00  00  00
> E733:  09  09  08
> E734:  00  00  00
> E735:  00  00  00
> E736:  10  10  10
> E737:  00  00  00
> E738:  00  00  00
> E739:  00  00  00
> E73A:  00  00  00
> E73B:  00  00  00
>
> E73C:  31  32  3F
> E73D:  28  28  28
> E73E:  29  28  32
> E73F:  0F  08  08
> E740:  31  30  24
> E741:  00  00  11
> E742:  19  19  19
> E743:  25  25  20
> E744:  00  00  00
> E745:  07  07  07
> E746:  00  00  00
> E747:  00  00  00
> E748:  10  10  10
> E749:  00  00  00
> E74A:  00  00  00
> E74B:  00  00  00
> E74C:  00  00  00
> E74D:  00  00  00
>
> E787:  BF  CD  BF
>
>
>
> wlevak@sdf.lonestar.org
> SDF Public Access UNIX System - http://sdf.lonestar.org
>
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