Re: Informations about JiffyDOS

From: Marko Mäkelä (
Date: 2001-03-16 09:02:08

On Fri, 16 Mar 2001, Spiro Trikaliotis wrote:

> For the BASIC portion, you're right; but the ROMs contain a second part, the
> KERNEL. The KERNEL starts at $E3xx, if I remember correctly.

It's $e4xx to be exact.  Video initialization is one of the first things
in the actual KERNAL.

> While there aren't really much differences with the BASIC part, except for
> what you have described and the USR()-vector, there ARE differences with the
> KERNEL part.

Yep, like in the jump table.  There's no $ff81 (CINT) entry in the VIC-20
ROM.  And VIC-20 has separate PAL and NTSC KERNALs while the C64 KERNAL
detects PAL/NTSC and has two copies of the RS-232C timing tables.

BTW, many routines in the beginning of the VIC-20 BASIC ROM are not
shifted by 3 bytes.  For instance, $AB1E is $CB1E on the VIC-20.


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