Search found 159 matches

by mc6809e
Tue Oct 14, 2014 2:38 pm
Forum: 680x0
Topic: Software sprites
Replies: 143
Views: 28929

Re: Software sprites

Do you mean the CPU must actually touch memory 64 times before the blitter starts again? it seems yes I thought the switch happened after 64 bus cycles whether the CPU used them or not. nope, thanks to STOP (and MUL/DIV) instruction I delayed every blitter pass (in Blit Mode) by thousands of cycles...
by mc6809e
Tue Oct 14, 2014 10:19 am
Forum: C / PASCAL etc.
Topic: C way to daisychain interrupts
Replies: 29
Views: 14287

Re: C way to daisychain interrupts

I wouldn't attempt that; goto outside the current function is undefined. Might "work", but then again it's not guaranteed to do so, and in such case it sure ain't prettier than a few lines of assembly code.. That depends on who is doing the defining! You're correct if you mean that comput...
by mc6809e
Tue Oct 14, 2014 10:11 am
Forum: 680x0
Topic: Software sprites
Replies: 143
Views: 28929

Re: Software sprites

Slightly OT, but what's the undocumented feature that gives a 65/128 split between blitter and cpu? interesting, what feature do you mean? I know that in Blit mode officially split is 64/64. But this is not correct because split is 65 (in case of MSTE 66 - 63+3) bus cycles for blitter and 64 bus cy...
by mc6809e
Mon Oct 13, 2014 11:12 pm
Forum: 680x0
Topic: Software sprites
Replies: 143
Views: 28929

Re: Software sprites

that doesn't have any impact. The only overhead is when blitter takes control over bus (one bus cycle in STE) and when release it (one bus cycle / STE). It is especially visible in Blit-mode. Unfortunately I'm no more able to verify that bus mastering in Falcon Slightly OT, but what's the undocumen...
by mc6809e
Mon Oct 13, 2014 5:45 pm
Forum: C / PASCAL etc.
Topic: C way to daisychain interrupts
Replies: 29
Views: 14287

Re: C way to daisychain interrupts

If you're using gcc you might be able to use a computed goto.

Save the old address in a void * and then when you've reached the end of your handler, do something like goto *old to transfer control to the old handler.
by mc6809e
Wed Oct 08, 2014 6:02 pm
Forum: 680x0
Topic: Drawing masked sprite using Blitter and single bitplane mask
Replies: 16
Views: 6477

Re: Drawing masked sprite using Blitter and single bitplane

Hi All, I use following code for my 64x64 pixel 4bitplanes sprites. I initialize blitter only once and in case of need just re-init it. Bitmap and mask aren't preshifted. In order to save some cycles I use HOG mode, NFSR bit, non-interlave bitplanes for sprite/mask organisation and 4bitplane mask. ...
by mc6809e
Sat Oct 04, 2014 7:53 am
Forum: MiST
Topic: MiST VGA upscaling experiments
Replies: 145
Views: 64394

Re: MiST VGA upscaling experiments

The trouble is that the signal is being sampled at a rate that isn't an integer multiple of the pixel rate. It's unlikely you'll find an inexpensive digital converter that's going to sync perfectly with the pixel rate. A better route might be to find a converter that will take the RGB output and con...
by mc6809e
Fri Oct 03, 2014 12:02 am
Forum: 680x0
Topic: Software sprites
Replies: 143
Views: 28929

Re: Software sprites

I guess this technique works better on the Falcon since the instructions are faster, can be cached and the number of bitplanes are higher. I'd like to see how bus arbitration is handled by the blitter hardware. The overhead might be slowing things down a bit. Anyone have any traces or latency numbe...
by mc6809e
Fri Sep 26, 2014 12:59 am
Forum: Games - General
Topic: Flashback on atari ST....
Replies: 154
Views: 45798

Re: Flashback on atari ST....

Well, a blitter means you don't have to pre-shift sprites, saving memory. In this case, there are lots of animation frames, which could add up to a substantial amount. Good point. This might explain the difficulty in doing the conversion -- limited memory for holding all possible preshifted sprites...
by mc6809e
Thu Sep 25, 2014 12:28 am
Forum: Games - General
Topic: Flashback on atari ST....
Replies: 154
Views: 45798

Re: Flashback on atari ST....

Because the poor 7MHz 1MB machine was just choked by the used virtual machine interpreting the game data. It is not about sprites or blitter at all, the 68000 alone is capable to move dozens of sprites on the screen at 50Hz. The bottle neck is the CPU. Same thing as the adventures from Sieera and o...
by mc6809e
Tue Sep 23, 2014 4:57 am
Forum: Games - General
Topic: Flashback on atari ST....
Replies: 154
Views: 45798

Re: Flashback on atari ST....

sorry to say but even if outrun don't have a single line of hardware code (like blitter or copper) in it , then it still does not mean that it was ported from the Atari. you could still make games on the Amiga that did not use any of those thing :) and to use your logic it would be the same to say ...
by mc6809e
Mon Sep 22, 2014 6:33 am
Forum: Games - General
Topic: Flashback on atari ST....
Replies: 154
Views: 45798

Re: Flashback on atari ST....

Outrun has a second MC68000 for a good reason so the best you can expect from a port is a game which "looks like Outrun" on the Amiga. first, it uses a second 68000 just because the arcade hardware allows it, and also because it made things more easy. Lotus turbo challenge 2 is exactly wh...
by mc6809e
Sun Sep 21, 2014 5:04 am
Forum: Games - General
Topic: Flashback on atari ST....
Replies: 154
Views: 45798

Re: Flashback on atari ST....

I don't understand what is so difficult on a couple of sprites moving over a static background. Look at the Turrican for example. There are dozens of moving objects over a freely scrolling background, somtimes even multilayered. The Flashback game is definitely doable on a plain ST and there will b...
by mc6809e
Fri Aug 15, 2014 7:17 pm
Forum: Games - Compatibility Issues etc.
Topic: Out Run - USA- version (Medway Boys crack)
Replies: 18
Views: 27579

Re: Out Run - USA- version (Medway Boys crack)

Outrun was a strange game. The original had 67 files but Automation one-parted it to improve loading time and compression so they could fit more games on the menu, but it was 1 meg only. The Medway Boys version is indeed 512k. If I still wanted to run Outrun off a floppy on a half meg ST I would us...
by mc6809e
Mon Aug 11, 2014 6:29 pm
Forum: Hardware
Topic: Memory access time
Replies: 57
Views: 14816

Re: Memory access time

ST was build as Apple Macintosh competitor and not Amiga . in 1983/84 the ST designers rather they had no idea about Amiga and its hardware details. I think your timeline is off. dadhacker who worked on the ST project relates that in July 1984, when Jack Tramiel took over Atari, that engineers were...
by mc6809e
Fri Aug 08, 2014 4:25 am
Forum: Hardware
Topic: Memory access time
Replies: 57
Views: 14816

Re: Memory access time

Fundamentally bitplanes are mostly a crappy idea, especially if: - all your modes are power-of-2 bits per pixel - games are a fundamental target of the machine - most of the graphics work is done in software Oh, look what that describes. Using chunky pixels wouldn't have increased hardware costs. I...
by mc6809e
Thu Aug 07, 2014 7:17 pm
Forum: Hardware
Topic: Memory access time
Replies: 57
Views: 14816

Re: Memory access time

npomarede wrote:Really, having coded a lot of demo effects both on ST and Amiga, I don't see many cases were interleaved bitplanes give an advantage.


Fair enough. I'll take your word for it.
by mc6809e
Thu Aug 07, 2014 6:25 pm
Forum: Hardware
Topic: Memory access time
Replies: 57
Views: 14816

Re: Memory access time

What about the case where two planes are modified? Sequential access lets you do long writes to modify two planes. That's a win. A one color sprite just doesn't seem worth the effort, but a three color sprite is much more useful. Besides, so little data is moved in the one color case that the slowd...
by mc6809e
Thu Aug 07, 2014 2:23 pm
Forum: Hardware
Topic: Memory access time
Replies: 57
Views: 14816

Re: Memory access time

That's why I put the word "weird" in quotes. It's been called weird, but I agree with you. It is better. Try to explain that to all demos / games coders that once wanted to alter only one bitplane as fast as possible and had to use things like "move (a0)+,(a1)+ and addq #6,a1" i...
by mc6809e
Thu Aug 07, 2014 1:08 pm
Forum: Hardware
Topic: Memory access time
Replies: 57
Views: 14816

Re: Memory access time

etc is interesting in that the Ataris can take advantage of the "weird" interleaved bitplane arrangement of the Atari's video memory. why "weird"? From my point of view this is much better/faster video organization than Amiga's one. That's why I put the word "weird" in...
by mc6809e
Wed Aug 06, 2014 5:26 am
Forum: Hardware
Topic: Memory access time
Replies: 57
Views: 14816

Re: Memory access time

The bandwidth available to the Falcon and other faster Ataris vs the Amiga 1200, etc is interesting in that the Ataris can take advantage of the "weird" interleaved bitplane arrangement of the Atari's video memory. The sequential nature of the interleaved bitplanes means a machine like the...
by mc6809e
Thu Jul 31, 2014 12:25 pm
Forum: Games - General
Topic: Flashback on atari ST....
Replies: 154
Views: 45798

Re: Re:

At the very worst the Amiga would be (113*313-4000)/(128*313) = 0.783 times the speed of the ST in 5 plane mode. It's never that bad though as the Amiga's CPU can use any even or odd cycle that happens to be available so some instruction sequences end up taking fewer cycles on the Amiga than on the...
by mc6809e
Thu Jul 31, 2014 7:21 am
Forum: Games - General
Topic: Flashback on atari ST....
Replies: 154
Views: 45798

Re: Re:

Hum More computing power ? Not that much. actually, that obvious as the fact that Amiga has more power in term of blitting datas. E.g. in case of 4bitplan mode CPU in ST is faster by 11%, in case of 5bitplan mode by 32%. Therefore in case of data calculations we can't just depreciate ST. but probab...
by mc6809e
Fri Jul 25, 2014 5:03 am
Forum: Hardware
Topic: Problem with vertical Lines on a 520 STFM
Replies: 5
Views: 1696

Re: Problem with vertical Lines on a 520 STFM

Open it up and re-seat any socketed chips.

They can creep out of their sockets over time as the ambient temperature cycles.
by mc6809e
Wed Jul 23, 2014 6:59 pm
Forum: 680x0
Topic: The best way to do sprite collision detection
Replies: 22
Views: 11200

Re: The best way to do sprite collision detection

A more obvious solution as I've mentioned in other posts is to drop the frame rate down to 12.5 instead of 25fps. Whilst this does pretty much fix any obvious slowdown the sprite animations just look terrible. It may just be the case if after every optimisation I can think of has been done I'll jus...

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