Re: [stella] Fwd: Some Amiga URLs.

Subject: Re: [stella] Fwd: Some Amiga URLs.
From: Glenn Saunders <cybpunks2@xxxxxxxxxxxxx>
Date: Sun, 09 Sep 2001 20:58:36 -0700
I tried it on my machine and here's the report.

First off, the manual itself says it's not going to be compatible with a lot of games. It doesn't support:

-Indirect Jump instructions
-Bank switching
-Controllers other than first joystick and paddle
-Mid-frame collision checking

I don't know why these limitations exist...

One thing he says seems rather suspect:

"Unfortunately, emulating the Atari 2600's custom hardware takes up far more time than emulating its CPU, so the benefits of translation are hardly noticeable."

This is clearly a failure of vision. The translation also has to occur at the register-access level, mapping TIA calls to analogous Amiga HW registers and mini-subroutines which emulate the them.

The Amiga has, I believe, 8 hardware sprites per scanline. I don't know how wide they can get or whether they can replicate. They are multicolored which comes in handy. But right there that's enough to simulate 3-copy sprites and two missiles (sans the ball) without using bitmapped graphics at all. In cases where the 2600 overlays both sprites the Amiga can just use one sprite. I also believe that the Amiga sprites are twice as wide as the Atari's, so in a six-char routine you'd only need 3 sprites. It has 4-voice 8-bit sound hardware which is like a POKEY on steroids which is like a TIA on steroids. Its copper can change just about anything in mid screen and even on a lowly A1000 there is enough CPU time to probably do enough hardware calls in mid-scanline to emulate TIA hw calls, mapping these to equivalent Amiga alternatives.

It doesn't look like this emulation is attempting to do a scanline-by-scanline metal-banging approach the way it should. It looks like it's still building a bitmap each frame the way traditional PC emulators do it, which is why it requires AGA for the maximum colors per screen (rather than per scanline) that it will need. This is the altogether wrong approach on the Amiga which has a graphics system that was designed for on-the-fly changes per scanline and mid-scanline (i.e. copperlists, HAM, etc..). Nevertheless, it's certainly the easiest approach to take if you don't want to get into the intricacies of the low-level Amiga hardware.

Even worse, the games it says work don't when I try to convert them. I tried Fantastic Voyage because I couldn't figure out how to concatenate files to make 2K games 4K games and it failed during translation.

Okie Dokie did run and reportedly at 98% fullspeed. I don't know if it's an inaccurate counter or what, but assuming it is an accurate count that's pretty lame that it's still not 100% on a superlowres (320x200) screen with a largely static display and my system is the very top end as far as 680x0 Amigas go.

So I'm not particularly impressed.

The author's name is Neil Cafferkey and if you want to email him: caffer@xxxxxxxxx

At 10:46 PM 9/9/2001 -0400, you wrote:
Sorry for responding to myself, but...

I noticed that Bob Colbert's Okie Dokie is part of the Electrostatic distribution.. Pretty cool (assuming he gave permission :)

Has anyone with an Amiga used this program before? Comments?

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