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Unicorns season: Prince of Persia for the A8!


rensoup

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14 minutes ago, rensoup said:


 

Hopefully the A8 is versatile enough to run an arcade game made for a much more powerful hardware (except for that horizontal resolution)
 

That's exactly the point.

The Atari is based on a 1970s plus NTSC limits development. 

Arcade is dedicated HW in all aspects.  

So they played rather more with higer resolution that with available colors. 

The 16 Bit machines changed that and brought the value of a good color palette into the gameplay. 

The Atari has "resolution" limits, while the palette can help a lot to have things really stylish. 

PoP lives by the stylish colors....

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18 hours ago, rensoup said:

I'm going with a conversion to C# first so I'll be hopefully able to carry out higher level optimizations later. I gradually convert Z80-> C# subroutines then I do simple interception calls to bypass the Z80 code and call the new C# code. It's not perfect though and it's pretty horrible to convert code that does all sorts of bit manipulation too.

 

I'm curious how the ZX spectrum Z80 @3.5Mhz compares with the the A8's 6502. I don't have much experience with the Z80 but its instruction set seems way more efficient than the 6502 perhaps at the expense of taking many more cycles per instruction ?

That sounds like an interesting approach and probably a way to save your sanity during the conversion process ;)

 

Based on my experience, you do things differently on those two processors. 6502 has like more bandwidth towards memory when you work with lookuptables or doing simple operations between kind of two arrays in memory etc.
Z80 is king of registers. You got like dozen 8bit/16bit registers that you can mix for all different kinds of purposes. Problems arise when you need to do complex things through accumulator (A register). It's a bottleneck when everything has to go through it towards memory and back. So you try to avoid it, load as much data possibly into registers and work on them directly without touching memory. Then it's crazy fast. 3d stuff on z80 is visibly faster compared to similar 6502 machine.

And then comes z80 specialty which is stack. 16bit counter registers give you nice way to do large loops, then you do stuff like pull 16bit from stack, pull another 16bit from stack (once), now you have 4 bytes of screen data inside processor. Then you do loop of unrolled push 16bit, push 16bit and you get things like scrolling Cobra, Sidewize, R-type etc games on spectrum. For a machine that has no hardware scroll at all, not even raster interrupts, it's crazy imho :)

 

Nice read on that topic is series of articles over here about Sidewize:

https://blog.stevewetherill.com/2022/02/more-sidewize-and-some-cool-cspect-stuff.html

 

So you're on the right track with that z80->c# conversion imho. Once you isolate smaller functions that do one thing, you convert them to 6502 code in some other optimized way (not a straight forward conversion of z80 instructions one  by one) and you may have a chance :)

Wish you all the best in development process !

Have fun :)


 

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On 5/7/2022 at 4:35 PM, popmilo said:

For a machine that has no hardware scroll at all, not even raster interrupts, it's crazy imho :)

 

Nice read on that topic is series of articles over here about Sidewize:

https://blog.stevewetherill.com/2022/02/more-sidewize-and-some-cool-cspect-stuff.html

Interesting, seems like they took the ZX architecture and built the AtariST around it ? (with bitplanes, just to make it even worse!)

 

 

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12 hours ago, invisible kid said:

This title caused me to get additional equipment to play on real hardware! The demo intro too. Love the music by Makary. This song, and the music from Drunken Chessboard(sorry don't know names) are my top two Atari tunes. Thanks for producing for vanilla hardware and thanks for making it happen!

 

 

@invisible kid  it is a fantastic game and yeah the pre game intro music above is damn good. I wonder if you have an XEX of this track you could post up?:D

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8 hours ago, Beeblebrox said:

@invisible kid  it is a fantastic game and yeah the pre game intro music above is damn good. I wonder if you have an XEX of this track you could post up?:D

https://demozoo.org/music/165122/

 

Worth checking out as the original runs @200hz which help the bass a little. The RMT file might be available on ASMA too?

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2 hours ago, invisible kid said:

Awesome! Seems to run fine on a 48k 800. Did a quick poking around and did not see it listed in SAP, but it could be named something that I didn't think of.

It might only be available in the updated ASMA zip archive ( http://asma.scene.pl/  which seems to be down right now)

 

...or I might have ripped it off straight from the XEX (which can be done in a few clicks with RMT2LZSS too!)

 

2 hours ago, invisible kid said:

Was the video and audio of the demo created together? Or did you write the video to match the beginning audio. It's timed so perfectly.

Not at all, Makary wrote the tune years before I even started coding on the A8 :).

 

Basically I had ideas for a bunch of effects and tried to figure out how to make them fit to the tune's tempo. I find good tunes to be a powerful source of motivation for creating demos... There are still a bunch of tunes I'd like to use too ;)

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14 hours ago, xxl said:

 

 

perhaps Makary is not well-known enough, perhaps he will make his work more familiar:

 

https://makarybrauner.bandcamp.com/album/yokey-pokey

Wow, some amazing tracks here -  from what I listened to so far Prism and Broken thoughts are amazing. I am a massive Radiohead fan and in some respects there are elements of Radiohead in these chips tunes in terms of the experimental aspect to the, like on the track Fiasco! Just listening to it now. Thanks for posting the link! Would love to get my hands on these to play on real hardware. :lust: I appreciated Makary is selling the tracks of course. 

Edited by Beeblebrox
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somewhat related to the topic:

 

PoP Megadrive hack to make it feel more like the original... Makes me wonder if there's a 6502 emulator powering that version

 

 

 

And apparently there's an unreleased PoP2 on the MD from Microids (who did the CPC version)

 

 

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On 5/13/2022 at 10:10 PM, rensoup said:

Interesting, seems like they took the ZX architecture and built the AtariST around it ? (with bitplanes, just to make it even worse!)

 

 

So not just me thinking the same ? esp the 2+ with same music chip… ?… but me is an STE guy so I am more used to DAC, Blitter, Softscrolling, 4096 palette…

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Ex C= people would have done most of the engineering work.  The Spectrum was practically unknown in the US so I doubt the heritage theory.

The crappy YM/Ay chip - plenty of computers, consoles and arcade games used it.  For a time it was the chip of choice since SID and Pokey were never used outside their companies of origin and there weren't many alternatives until the proper synth chips became cheap and available in the mid-late 1980s (coincidentally with some of the good ones by Yamaha)

Edited by Rybags
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On 7/9/2022 at 7:13 PM, invisible kid said:

This title caused me to get additional equipment to play on real hardware! The demo intro too. Love the music by Makary. This song, and the music from Drunken Chessboard(sorry don't know names) are my top two Atari tunes. Thanks for producing for vanilla hardware and thanks for making it happen!

 

 

If you haven't heard it with the audio out to a home Hi-Fi stereo with good bass, and other ranges, then you haven't heard how awesome it really is. Even better are Pokey stereo and quad tunes. Nothing beats a Pokeymax with quad pokey's hooked up to a Hi-Fi system for gaming and music/demos.

Edited by Gunstar
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On 7/14/2022 at 3:52 PM, Rybags said:

Ex C= people would have done most of the engineering work.  The Spectrum was practically unknown in the US so I doubt the heritage theory.

The crappy YM/Ay chip - plenty of computers, consoles and arcade games used it.  For a time it was the chip of choice since SID and Pokey were never used outside their companies of origin and there weren't many alternatives until the proper synth chips became cheap and available in the mid-late 1980s (coincidentally with some of the good ones by Yamaha)

Weird that a guy who worked on the C64 (https://en.wikipedia.org/wiki/Shiraz_Shivji) designed the ST in such a way... But apparently the ST's code name was "Rock bottom price" :lol:

 

Rambling again but yeah Dual pokey instead of the YM as well as a super ModeE (4bits per color at 320x200) would have made the ST a much better competitor compared to the Amiga and at a bargain price.

 

On 7/14/2022 at 3:46 PM, Heaven/TQA said:

So not just me thinking the same ? esp the 2+ with same music chip… ?… but me is an STE guy so I am more used to DAC, Blitter, Softscrolling, 4096 palette…

Pure CPU power has that flexibility and can beat custom HW as long as the graphics memory layout makes sense (think VGA 256 colors which was the simplest design ever... unfortunately they forgot to give it bandwidth !)

 

On 7/14/2022 at 4:15 PM, invisible kid said:

I can't get over it, SID doesn't sound as full as that does it? Don't have too much experience with it.

I don't know, I enjoy this one though ;-)

 

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9 hours ago, rensoup said:

Weird that a guy who worked on the C64 (https://en.wikipedia.org/wiki/Shiraz_Shivji) designed the ST in such a way... But apparently the ST's code name was "Rock bottom price" :lol:

 

Rambling again but yeah Dual pokey instead of the YM as well as a super ModeE (4bits per color at 320x200) would have made the ST a much better competitor compared to the Amiga and at a bargain price.

 

The ex-commodore engineers that went to Atari with Jack had 6 months to throw together the ST. Jay Miner had about 6 years to design the Amiga, starting right after he left Atari, after doing the 400/800 computers. The ST would have been better if they had as much time to design it as they did the C64. Commodore had no choice, after Jack left and stole their engineers, but to buy the Amiga out from under Atari, or get caught with their pants down. 

 

And the ST designers couldn't very well make a SID II, if they even had the time, since it was Commodore's property. And I doubt they had any clue about how good the Pokey was, compared to the Yamaha chip and neither did Jack. To expect them to look to a 5 year old 8-bit for what was the competition's "older" tech compared to their C64, for it's custom chips would have been sacrilege to their pride.

 

If Atari had gotten the Amiga, who knows if Jack and friends would have even used it though. The probably would have gained ownership of Amiga after their default and the Amiga would have gone onto a shelf as they still went ahead with a new computer of their own, albeit with more time since there would have been no threat of the Amiga in Commodore's hands. 

 

If Jack hadn't been ousted from Commodore I'm sure the 16-bit computer they would have designed at Commodore would have been very similar to the ST, but probably would have had a SID II and a VIC III under it's hood. And who knows if the Amiga would have ever made it into production by anyone once Atari Inc. had gone under without Jack there to buy up the consumer division.

 

As strange as it all was, It probably turned out for the best with Commodore getting the Amiga, and Atari throwing a machine together that would finally be more comparable to the original Amiga 1000 after another 4 years of improving the ST hack-job that finally became the STE with 4096 color palette and stereo audio and Blitter and MPU that should have been in the ST from the start to be a true competitor to the Amiga. Otherwise we probably would have a much different 16-bit machine from Commodore for better or for worse and no ST or Amiga at all, for better or worse (I can't imagine a 16-bit machine with a VIC III and SID II being better than the Amiga though. 

 

Only if Atari Inc. & Time Warner hadn't over reacted to the crash and run scared would we have had both an Atari Amiga and a Commodore 16-bit successor to the C64 that would have been better than the ST we got.

 

 

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14 hours ago, rensoup said:

Weird that a guy who worked on the C64 (https://en.wikipedia.org/wiki/Shiraz_Shivji) designed the ST in such a way... But apparently the ST's code name was "Rock bottom price" :lol:

 

Rambling again but yeah Dual pokey instead of the YM as well as a super ModeE (4bits per color at 320x200) would have made the ST a much better competitor compared to the Amiga and at a bargain price.

 

Pure CPU power has that flexibility and can beat custom HW as long as the graphics memory layout makes sense (think VGA 256 colors which was the simplest design ever... unfortunately they forgot to give it bandwidth !)

 

I don't know, I enjoy this one though ;-)

 

Yeah. STs 1 MHZ advantage over Amiga made a difference in some genres like 3d vector games... simply compare all those Amiga VS ST side by side videos. and yes... having more horsepower all remains to your software tricks... and the 1 MB while A500 was 512kb as default (and yes... I got an A2000, A500, A600, A1230... ;)) and me still thinks... interleave bitplanes or bitplanes alone are fuckery - big and was suprised side that SNES has them in tiles (up to 16 color mode).

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The margin was closer to 0.8 MHz and I suspect some of that would have been lost thanks to the interleaved bitplanes.

On the other hand the Amiga might have lost a little due to graphical DMA losses.

 

But overall the Amiga could probably have done better in 3D and vector applications thanks to the blitter but I suspect it probably went unused a lot of the time thanks to shared/similar code of ST releases.

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On 7/18/2022 at 9:22 AM, Gunstar said:

he ex-commodore engineers that went to Atari with Jack had 6 months to throw together the ST. Jay Miner had about 6 years to design the Amiga, starting right after he left Atari, after doing the 400/800 computers. The ST would have been better if they had as much time to design it as they did the C64. Commodore had no choice, after Jack left and stole their engineers, but to buy the Amiga out from under Atari, or get caught with their pants down. 

The ST was a decent design, it didn't require extra time I think, just some rewiring inside the Shifter (the ST's video chip). They went with bitplanes because everyone else did.

 

8bit computers were incapable of doing large block copies with the CPU. So you couldn't move the whole screen at 50fps, that's why HW scroll was invented. Moving a modeE screen (8KB) with the 6502 on a XL would take about 3 frames I believe...

 

The ST was different with a beast of a CPU: much higher clock frequency combined with a more efficient instruction set. The ST was capable of moving a block of memory the size of the screen (32KB) in about 2/3 or 3/4 of a frame if I recall correctly.

This means the ST could do software vertical scrolling easily, as well as horizontal scrolling in 16 pixels steps (which is way too fast to be practical).

 

Due to the bitplanes layout, it was also notoriously impossible to do fast 1 pixel horizontal scrolling on the 520ST because that required keeping 16 preshifted copies of the screen wasting  16x 32KB, or all the 520ST's memory :thumbsup:.

 

( Some games managed to get around that by preshifting 16x16 tiles pairs but it was still a pain )

 

The same had to be done for sprites, keeping 16 shifted copies in memory.

 

A super modeE, 16 colors at 320x200 (similar to the CPC but at 160x200 ?) would have involved rewiring the ST's video hardware slightly differently, keeping most of the design identical to the final HW. My guess is that the cost/complexity for that would have been identical (this was old tech after all)

 

The difference ? Fast vertical scroll, fast 1 pixel horizontal scroll (at the cost of 64KB instead of 512KB) costing the same amount of CPU time as the real ST. Fast sprite display (much lower CPU cost and much lower RAM requirements)...

 

On 7/18/2022 at 3:47 PM, Rybags said:

But overall the Amiga could probably have done better in 3D and vector applications thanks to the blitter but I suspect it probably went unused a lot of the time thanks to shared/similar code of ST releases.

 

...and faster 3D as well (because drawing lines slopes without bitplanes is easier/faster)

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