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Old 14 October 2019, 12:40   #12
Per aspera ad astra

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Join Date: Mar 2017
Location: Crossing the Rubicon
Age: 49
Posts: 2,442
Originally Posted by Chrille View Post
IIRC Dyna Blasters writes #$0000 for 50 Hz Pal to BeamCon0 ($DFF1DC) Register
and #$0020 for 60 Hz (NTSC) to BeamCon0 Register and you could change it by pressing space (or some other key?) in the menu (???).

AFAIK this is only possible for all ECS+ Agnus Amigas e.g. A600, A500+, A1200 and also on some A500 with Kickstart 1.3. (those Agnus where you can address 1 MB Chip Ram, even when it is located at $C00000 for CPU and therefore not usable for the OS).
No, it is not managed this way, just checked to control also if my memory was broken
I extracted and commented the relevant code.

	dc.l	$FFE1FFFE
	dc.l	$0401FFFE	; wait y==$104 position
	dc.l	$00960040	; 'pause' blitter (CPU can be hogged by BLTPRI)
	dc.l	$009C8010	; trigger copper IRQ
	dc.l	$01000000	; no bpls active

irq3:	...
	MOVE.W	$dff01e,D1
	BTST	#4,D1		; copper IRQ?
	BEQ.B	.skip		; no, skip
	MOVE.L	$dff004,D0	; beam position
	AND.L	#$ff0000ff,D0	; isolate LOF+I and x position
	ADD.L	#$00013610,D0	; skip $136-$104=$32=50 lines
	MOVE.L	D0,$dff02a	; write new position to V(H)POSW
	MOVE.W	#$8040,$dff096	; restart blitter operation

.skip	BTST	#5,D1
	BEQ.B	.skip2
This also works on OCS as opposed to using BEANCON0 (which is obviously much more convenient).

Yes, I've changed horizontal frequencies. If you change horizontal or vertical frequencies (other than vertical frequencies between 50 Hz to 60 Hz and horizontal 15,XX kHz) you need a multisync monitor (such as Amiga 1764, Amiga 1438, Mitsubishi EUM1491a, etc.). On other monitors it might be possible to slightly change the frequencies but not too much. I've tested this back in the days on my Phillips 88XX monitor. The monitor makes strange sounds if you change it too much

I've changed the frequencies in order to use all sprites on a resolution similar to productivty mode resolution (on AGA). The systems productivity mode is not appropriate for games with sprites at least if you want use all 8 sprites. Our first approach was to use a resolution with 640x512 Pixel x 64 Colors (or 640 x 256 x 64 Colors for non multisync monitors). We changed it later to 640x260 x 256 colors (so that we have to take no adjustments with 2 different resolutions) but we never finished the game and that's another story.
Ok, this confirms that you did not use VPOSW which is a completely different story than BEANCON0 and related registers
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