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Forums > CSDb Discussions > $e544 ?
2002-04-09 08:28
Dwangi

Registered: Dec 2001
Posts: 118
$e544 ?

Hope this is the right forum to put a question..

I have heard so much comments of what is right and wrong when setting up a multicolor screen (so it also work on old c64:s´)

lda color
sta $0286
jsr $e544

thats fuck up on an old c64 ???
 
... 6 posts hidden. Click here to view all posts....
 
2015-02-03 20:06
Zyron

Registered: Jan 2002
Posts: 2213
lda #col
sta $d021
jsr $e536

works on both old & new c64s. ;)
2015-02-03 20:35
lft

Registered: Jul 2007
Posts: 364
This behaviour is actually explained in Bagnall's On The Edge. Early revisions of the VIC had a problem where small dots of the foreground colour would flicker randomly all over the screen. Obviously, this would have given potential customers a really bad first impression of the C64. There was no time to fix the hardware, so they added a workaround to the kernal ROM, where the current background colour would be stored into all colour RAM locations corresponding to blank characters on the screen.
2015-02-03 20:47
tlr

Registered: Sep 2003
Posts: 1313
Quote: lda #col
sta $d021
jsr $e536

works on both old & new c64s. ;)


$e544 sets color mem to white in kernal rev1...
2015-02-04 07:14
JackAsser

Registered: Jun 2002
Posts: 1685
THIRTEEN YEARS BETWEEN TWO POSTS!!!! :D Horray for Zyron - The thread awakener! ***Svindlande***
2016-01-09 07:25
Stablizer

Registered: Jan 2016
Posts: 19
jsr $e544 just clears the screen. :)
2016-01-09 19:30
TheRyk

Registered: Mar 2009
Posts: 726
I find Zyron's hint kinda kewl and helpful to prevent old KERNAL Rev CLRSCR trouble, even after so many years :)

PS: Had funny experiences with this release and an old KERNAL rev compo machine hehehe
DuTreff
on old rev white on white as it uses $E544 CLRSCR
2016-01-10 21:15
Graham
Account closed

Registered: Dec 2002
Posts: 990
A "clean" and portable version would be:

clrscrn
        TAX
        LDA col2pet,X   ; convert color to PETSCII code
        JSR $FFD2       ; CHROUT

        LDA #$93        ; CLR (PETSCII code)
        JMP $FFD2       ; CHROUT

col2pet
        .bxte $90,$05,$1C,$9F,$9C,$1E,$1F,$9E
        .byte $81,$95,$96,$97,$98,$99,$9A,$9B


The col2pet table is not really required, the same table can be found in Kernal-ROM at adress $E8DA, hence:

col2pet = $E8DA

clrscrn
        TAX
        LDA col2pet,X   ; convert color to PETSCII code
        JSR $FFD2       ; CHROUT

        LDA #$93        ; CLR (PETSCII code)
        JMP $FFD2       ; CHROUT
2020-06-04 08:28
Dwangi

Registered: Dec 2001
Posts: 118
Hi

Thanks for all the answers.
I never use ROM:s myself. I asked because alot of demos between 1987 and 1992 (and even some games) displayed single colours on an old C64 were it should be multicolours.

I have also seen alot of coders trying to teach other how to do it "right".

For example in this demo.
Lunacy 6 by Antic.

Anyway seems like this topic should have been in the coders section. Sorry for this.
2020-06-04 08:47
JackAsser

Registered: Jun 2002
Posts: 1685
Quote: Hi

Thanks for all the answers.
I never use ROM:s myself. I asked because alot of demos between 1987 and 1992 (and even some games) displayed single colours on an old C64 were it should be multicolours.

I have also seen alot of coders trying to teach other how to do it "right".

For example in this demo.
Lunacy 6 by Antic.

Anyway seems like this topic should have been in the coders section. Sorry for this.


<3
2020-06-04 09:06
Count Zero

Registered: Jan 2003
Posts: 1110
Resolved after 18 years I assume.
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