Search found 159 matches

by mc6809e
Sat Apr 06, 2013 6:51 am
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 575
Views: 143200

Re: horizontal scrolling on ST

It's tIme to speak about code ! about timing : nb of 16 pixels block 320 pixels line shift addxscroll32 roxrscroll32 roxmscroll addxscroll32 roxrscroll32 roxmscroll 1 105,8 109,8 63,6 2116 2196 1272 2 111,8 119,8 2236 2396 From the source code it looks like addxscroll32 takes 120 extra cycles per 3...
by mc6809e
Fri Apr 05, 2013 3:05 am
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 575
Views: 143200

Re: horizontal scrolling on ST

I agree your statement if speaking of shifting and/or rotating values, but in a scrolling you must add pixels from previous/next 16 pixel block depending of the direction of the scrolling (unless your background is painted with always the same 16 x .. pixels tile, but that's cheating). "Calcul...
by mc6809e
Tue Apr 02, 2013 11:06 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 575
Views: 143200

Re: horizontal scrolling on ST

so this is unintentional omission in hardware design?? I don't think so. I just don't think hardware assisted graphics was a design goal, so they did what was minimally required. The ST came into existence to provide a low cost 68000 alternative to the Amiga and Macintosh. It was meant to be a simp...
by mc6809e
Tue Apr 02, 2013 7:30 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 575
Views: 143200

Re: horizontal scrolling on ST

That's the way I did it. Just threw bytes at the screen. As mc6809e says, works fine at 25fps but it's very hard to do 50fps unless you cut the window size down a lot. and "256 bytes" boundary limit for video address is because low/or high part of video register is not writable ? right? A...
by mc6809e
Tue Apr 02, 2013 4:23 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 575
Views: 143200

Re: horizontal scrolling on ST

This to me is THE trick to get high frame rates on the ST. The 68000 is mostly memory bandwidth limited so the fastest rates are obtained by simply minimizing the number of memory accesses. Sure, but it's only useful in games where the playfield is static. I moved to it for the PC version of Starba...
by mc6809e
Mon Apr 01, 2013 3:58 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 575
Views: 143200

Re: horizontal scrolling on ST

It changes the design challenge of the app a lot - you tend to use draw/undraw dirty region sprites rather than a repaint-every-frame architecture. This to me is THE trick to get high frame rates on the ST. The 68000 is mostly memory bandwidth limited so the fastest rates are obtained by simply min...
by mc6809e
Sat Mar 30, 2013 4:26 pm
Forum: 680x0
Topic: STE Blitter and Interrupts
Replies: 49
Views: 9371

Re: STE Blitter and Interrupts

There's an unfortunate problem that arises when using shared mode and any code that depends on counting horizontal lines. This problem can be especially difficult to debug since it happens infrequently. Maybe it's related to your problem. As you know, in shared mode the CPU and blitter take turns ac...
by mc6809e
Tue Mar 26, 2013 2:57 am
Forum: 680x0
Topic: STE Blitter and Interrupts
Replies: 49
Views: 9371

Re: STE Blitter and Interrupts

I'm still stuck for a solution to this flickering timer b problem. At this point I think I would simplify things a bit and just change the background palette register in your timer-b handler to see when the CPU is becoming available during concurrent blit/interrupt. You can learn a lot about your c...
by mc6809e
Thu Mar 14, 2013 4:56 pm
Forum: 680x0
Topic: Lance 12.5 / 25 / 50 KHz routine for STE (V13)
Replies: 71
Views: 20288

Re: Lance 12.5 / 25 / 50 KHz routine for STE

I wonder how it works when a MOD player change the fequency on a sample for each individual note it's playing. It feels like it should take alot of CPU time to recalculate the sample frequency and that must be done on the AMIGA aswell so how can it be so fast? Paula on the Amiga has a simple counte...
by mc6809e
Fri Mar 08, 2013 1:53 am
Forum: 680x0
Topic: Lance 12.5 / 25 / 50 KHz routine for STE (V13)
Replies: 71
Views: 20288

Re: Lance 25 KHz routine for STE

Hi ! Following some coding talks at DHS, i made a 25 KHz version of the famous Lance 50 KHz MOD replay routine. It saves only about 5% CPU time compared to the 50 KHz version. All work done without an STE, under STeem with Devpac 1.24. Enjoy it and use it if you want. Bye, Paulo. PS: updated with t...
by mc6809e
Tue Feb 19, 2013 4:44 pm
Forum: 680x0
Topic: Interrupt friendly IKBD routine?
Replies: 22
Views: 4781

Re: Interrupt friendly IKBD routine?

What if you only enable the IKBD interrupt for, say, 150 scanlines mid-screen? That is more or less what I was doing. I turn it on after the top border is opened and turn it off before the bottom border is opened. It seems to work with normal game play, but if I move the joystick as fast as I can i...
by mc6809e
Thu Jan 03, 2013 2:23 pm
Forum: Chat forum [ENG]
Topic: Another Amiga comparison...Timer B vs Copper
Replies: 19
Views: 3933

Re: Another Amiga comparison...Timer B vs Copper

My experience with the Amiga was pretty much that it could do a lot more with fewer operations (be that clock cycles / sources / events) than the ST or STE for realtime 2D stuff, but it was a frustrating system for 3D programming because there were fewer cycles available and the extra hardware wasn...
by mc6809e
Wed Jan 02, 2013 1:51 am
Forum: Chat forum [ENG]
Topic: Another Amiga comparison...Timer B vs Copper
Replies: 19
Views: 3933

Re: Another Amiga comparison...Timer B vs Copper

what software use delta compression in HAM animation? The earliest example was the juggler demo in 1986. The ANIM file format also uses delta-frame animation. I never saw anything like this: sprites over HAM image! why? only static images... after 30's years of HAM... (btw: I always take for grante...
by mc6809e
Tue Jan 01, 2013 5:53 pm
Forum: Chat forum [ENG]
Topic: Another Amiga comparison...Timer B vs Copper
Replies: 19
Views: 3933

Re: Another Amiga comparison...Timer B vs Copper

Isn't it very difficult to create a HAM image? Since the colors are depending on the colors next to them. I read somethere that originally the HAM mode was suppose to be different and much more flexible but they had some problems or couldn't finish it in the way they had wanted it to work so it got...
by mc6809e
Tue Jan 01, 2013 5:41 pm
Forum: Chat forum [ENG]
Topic: Another Amiga comparison...Timer B vs Copper
Replies: 19
Views: 3933

Re: Another Amiga comparison...Timer B vs Copper

hm... but for what you could use 75% of CPU free time while you displaying HAM image? HAM is useless for animation, sprites... anything except displaying static image. (except HAM Animation = displaying series of HAM images :)) Many HAM animations use a form of compression called delta-frame animat...
by mc6809e
Mon Dec 31, 2012 7:10 pm
Forum: Chat forum [ENG]
Topic: Another Amiga comparison...Timer B vs Copper
Replies: 19
Views: 3933

Re: Another Amiga comparison...Timer B vs Copper

I always wonder why on Amiga nobody use same trick for displaying images in 4096 colors as on STe?!? I am sure that Spectrum4096 converted from 24bit image looks better than HAM images. Especial with latest work from Doug (or petari with video). and on Amiga it would be even easier to achieve this ...
by mc6809e
Mon Dec 31, 2012 6:34 am
Forum: Chat forum [ENG]
Topic: Another Amiga comparison...Timer B vs Copper
Replies: 19
Views: 3933

Re: Another Amiga comparison...Timer B vs Copper

Yes I know it's more advanced than using Timer B, but how many games used it to change the screen mode / width per line, set the hardware scroller multiple times per line and so on. I mean that if it was used for simplier stuff like rasters in 90% of the cases, when it is more or less equal to what...
by mc6809e
Wed Dec 12, 2012 3:19 am
Forum: Hardware
Topic: ST vs Amiga : advantages/disadvantages
Replies: 180
Views: 37696

Re: ST vs Amiga : advantages/disadvantages

I'll post the code when I get home next month. I'll have access to an a500 with fast RAM then. I think I'll raster time the blitters on a general bit copy too. I'm sure the ST is going to easily outrun the Amiga on a fringed copy. I'm sure the Amiga will outrun the ST on a complex mask operation bu...
by mc6809e
Thu Nov 08, 2012 4:59 pm
Forum: Games - General
Topic: the Shadow of the Beast 2 thread
Replies: 15
Views: 2942

Re: the Shadow of the Beast 2 thread

I've been looking at some less obvious ways to get >16 colours on an ST screen without excessive CPU overhead. And no I don't mean rasters or fiddly spectrum-512/PCS style timing stuff. It's really a combination of some math/algorithms, some rather heavy computation / preprocessing and a few layers...
by mc6809e
Sat Aug 25, 2012 4:30 pm
Forum: Coding
Topic: 4096 colors
Replies: 143
Views: 33915

Re: 4096 colors

So are you saying that an additional / alternate form of sync is required before starting an external device, versus normal CPU bus cycles? and that it's due to the *internal* clock? cheers If you want writes to the palette registers to be perfectly timed so that they correspond to particular posit...
by mc6809e
Sat Aug 25, 2012 3:03 am
Forum: Coding
Topic: 4096 colors
Replies: 143
Views: 33915

Re: 4096 colors

I had looked at blitter based palette loading and overscan stuff before I stopped work on PCS but I have been revisiting it again just now. The blitter is a headache to stabilize and the only way I got it to work on my test machine at all was to use fairly conservative colour allocation rules. You ...
by mc6809e
Fri Jul 20, 2012 7:46 pm
Forum: Games - General
Topic: Audio vs Amiga
Replies: 105
Views: 22522

Re: Audio vs Amiga

Would it be possible to make a new "MOD" format just for Atari that could be handled differently and maybe without time consuming effects. Something just for games there you need high speed and maybe not all kinds of effects. Special effects don't consume much time. Reading samples, mixin...
by mc6809e
Thu Jul 19, 2012 10:32 pm
Forum: Hardware
Topic: ST vs Mac : advantages/disadvantages
Replies: 155
Views: 36200

Re: ST vs Mac : advantages/disadvantages

The original Macintosh architecture greatly crippled the 68000. Some of you may have followed the ST versus Amiga discussion where the issue of memory accesses by the CPU was an issue. Both of those machines allow the memory controller to deliver a new word to the CPU every 4 CPU cycles (assuming a ...
by mc6809e
Wed Jul 18, 2012 9:26 pm
Forum: Games - General
Topic: Audio vs Amiga
Replies: 105
Views: 22522

Re: Audio vs Amiga

Another test is to execute a loop containing a run of (512, for instance) CLR.L D0 instructions. If the CPU can only access memory on "even" cycles, then the average number of CPU cycles per CLR.L D0 instruction will be slightly more than 8 cycles instead of the 6 mentioned in the Motorol...
by mc6809e
Wed Jul 18, 2012 6:37 pm
Forum: Games - General
Topic: Audio vs Amiga
Replies: 105
Views: 22522

Re: Audio vs Amiga

And even then, the Amiga allows the CPU access to odd memory cycles when they're available and requested while the ST forces the CPU to wait. Amiga Hardware, in Blitter section states that 68000 instruction are always rounded to 4 (even cycles) by Amiga hardware: Some 68000 instructions do not matc...

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