Interlace mode: More line, more dma slots?
With interlaced mode, do we have more dma slots cos more line?
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No. The number of lines per frame is the same.
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Actually you one or half (depending on how you want to count them) lines less because interlace is alternating 313 and 312 line fields. Normal non-laced is 313 lines.
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Can you actually enable bitplanes for one more scanline during the long frame?)
Btw off topic but does (win)uae support flickering the scanline filter so that current frame is bright and previous frame is dark? |
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Why do you want to see a one more scanline? (actually you can write to VHPOSW to increase/decrease lines, but so you also change video frequency ;)) [if I'm not wrong Dyna Blaster do this to fake a quasi-NTSC mode on PAL Amiga] |
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Has anyone ever tried to change the horizontal frequency? EDIT: now that comes to mind, and if I remember correctly, there is a demo that does it to make an effect with the copper! (only a little change to x value to shift initial copper position) But to not lost sync every other line reset the position. |
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But it should be feasible only time tight Copper list required, perhaps CPU heavy usage too... anyway i observed horizontal frequency changes (HV transformer begin to sound very weird) - today no risk for LCD but those times i couldn't afford to broke TV. Also curios about triggering with Copper STRHOR - $DFF03C - (this could trig Paula higher sampling rate) - tried but fail was obvious - whole system halted (tried with CPU - perhaps Copper in middle of line could do something better). |
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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). Quote:
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. |
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I extracted and commented the relevant code. Code:
copperlist: Quote:
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https://www.youtube.com/watch?v=BhVsVjNIqSU Fast forward to 11:45. The copper effect on the upper part. |
Yes, this topic is about almost undocumented way to change refresh rates that does not require ECS.
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Issue is horizontal timing as it is most demanding from time domain characteristic (lot of Amiga things seem to be hardwired to HSync). As i wrote before - whenever vertical was easy to modify then horizontal was almost immediately penalty - or system hang, or loosing display, at best horizontal line distortions (it looks like only few lines in middle of screen disturbed for a while). ECS/AGA is easy peasy when compared to OCS. Quote:
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@pandy71
With extended refresh rate, dma slots don't changes? I mean, we have more lines... |
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BTW the cracked version of Wings of death controls via the CTRL key the switching between PAL/NTSC. |
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Are DMA and horizontal display sync also affected? So if I change horiz. position to 0 in the middle of the line, will the hardware start a new DMA cycle (refresh, audio..)? And if I set it to $0D, will it restart with audio DMA only? :) |
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So there is a crazy code that sync in every line the CPU with BEAM position and change accordingly VHPOS. This is because the copper cannot wait for odd positions (best precision from the mask is #$fffe), this corresponds to 4 pixels in low resolution. But if you 'shift' the x position of a single CCK the odd position become even (this is 2 'pixels after' a normal wait)! Therefore: before BPL DMA fetches write a value that is one CCK after video position, after the last fetch realign the position. Quote:
Pandy71 tests are discouraging.. Maybe Toni can enlighten us. |
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