Wolfenstein 3D IS technically possible on stock A500 shocker!

[KThunder]

I have two games for the genesis that are the same basic thing: Zero Tolerance, and Beyond Zero Tolerance. Both run quite well and have no extra chips in them for processing or anything. They aren't full screen but are quite playable.

here is a link:
http://en.wikipedia.org/wiki/Zero_Tolerance_(video_game)

IO have the actual cart for Zero Tolerance, just the rom for BZT. Both were released by the developer for free.

[KThunder]

Very nice!

When I asked my parents for an A500 as my Christmas present in 1989 they told me they couldn't afford it and I should choose something else.

I went through my Mum's shopping catalogue and saw an Atari 8-bit (Dunno which model) and thought it looked cool and asked for that or a SAM-Coupe.

I was ecstatic on xmas morning to find an A500 Batpack!

I've always wondered what they Atari 8-bits were like though as other than my Lynx I never owned one.

I saved my paperboy money for a year to buy an Atari 600xl. It was fun to program, and great for games. The NES had it beat for games though.

[KThunder]

Was the 800XL the top model?

Yeah in the early 80's the 800xl was the top. The 600xl I bought off a friend ended up having a problem with the keyboard so he gave me his 800xl instead. Both were pretty good computers though, and the floppy drive was much faster than the c64 and 1541; which I got a bit later.

Mid to late 80's the xe ataris came out with more memory but really were more like the 64c being different than the c64. Not much better or worse, just a slicker case and a different number.

[KThunder]

Planar graphics, we has them!

From a CPU perspective, it's a go; the 68000 will most likely perform just as well as an old 286. What else do we have? Memory? I don't know anything about the memory performance of OCS Amigas, or 286 PC's for that matter. I'm sure someone else here can enlighten us, but regardless, I think both platform have enough juice.
Both the Amiga and the 286 will be able to play sounds over DMA (assuming that piece of PC junk has a soundcard), no problem there.

The only difference is the video hardware. I'm no expert, but having to do several writes to fill each pixel, when the PC only needs to do it once seems like major disadvantage for the Miggy. Thus, we need to rely on c2p conversion to get things done at a reasonable speed.

The question is: Can one of you clever coders get blazing fast c2p conversion done on a 68000? Or can you do some miraculous planar 3d engine? If not, we will have to accept that our beloved little miggies were behind even contemporary PC's, at least in some aspects.

There is one way around writing multiple writes for a single pixel, but it isn't very good: 2 color graphics. You can use sprites to color things up, and a copper list to provide some "shading" top to bottom but thats about it.

Unfortunately C2P on a 68000 can't go fast enough. 4 color might be close but that is 4 writes per pixel, in addition to the half dozen instructions needed to calculate the pixel in the first place.

[KThunder]

The "PC" was not ahead in the beginning. Look at the original spec of VGA and you will find planar gfx also. The Amiga gfx were ahead of the original VGA spec. The difference was the amazing advance of PC gfx from VGA to super VGA to 3D accelerated Voodoo gfx before the Amiga could even get AGA or chunky modes that left the Amiga in the dust....

The mode most used in Vga that is called planar is mode x, and it works a bit differently (better) than the amigas planar mode. here is a quick description of it:

http://en.wikipedia.org/wiki/Mode_X

notice two lines in that article:

Planar memory arrangement splits the pixels horizontally into groups of four. For any given byte in the PC video memory aperture, you can access four pixels on screen, by selecting the plane(s) you require.

Planar mode allows up to 4 adjoining pixels to be modified in one byte write operation, which is ideal for solid filling of objects such as polygons, rectangles, lines, etc.


Mode x was tricky to handle but could actually be faster than chunky graphics. On the Amiga Planar graphics are always slower for this type of operation. The way the Amigas graphics hardware was setup made mode x impossible or not any faster

here is a really in depth programming article on mode x:
http://www.gameprogrammer.com/3-tweak.html

[KThunder]

Eh, mode X isn't planar so much as a strange hack to use the planar memory mapping hardware in chunky mode (the advantage being that it gives you access to all the video RAM, which you don't get from the BIOS-supplied linear-framebuffer chunky mode.) Actual VGA planar modes are the 16-color high-res modes and the EGA-compatibility modes.

The documentation I provided that showed exactly what mode x was and why it was so fast. It is a planar mode, it is much faster, and it was present in even the earliest vga systems. You could call it a hack, but it was used so extensively in games, and programming books; it was a very well known, well documented, well used hack.

The big thing I guess is that IBM provided both planar, and chunky modes in hardware and in the bios, and with a "hack" you could access 4 pixels simultaniously. The Amiga only had pure planar modes and was pretty much the opposite, instead of 4 pixels at a time, it took 4 writes per pixel, in 16 color mode.

If all Amigas had the CD32's Akikko chip they would have a similar mechanism.

here is a link for that:
http://en.wikipedia.org/wiki/Akiko_(Amiga)

[KThunder]

Ooh that brings back some fond memories of the 90's for me.

I never tire of reading this book:

http://www.drdobbs.com/high-performance-computing/184404919;jsessionid=14VZ5MDXC5NHRQE1GHPSKH4ATMY32JVN

Nice, I'll have to check that site out.

I have a ton of old programming books, that have lots of info on EGA, VGA and early SVGA modes including the first VESA versions.

I think it is cool that these video modes are still with us today, my newest video card is a geforce 9 series card and it can still run CGA stuff.

[KThunder]

I thought the point of fast C2P was to calculate a chunky buffer of graphics data 16 pixels wide (32 on AGA, any height as Wolf3D/Doom engines are column rendered due to the ray casting mechanism), and then do the C2P on this buffer into planer graphics memory? You still do the write per plane, but you do it for 16/32 pixels at a time rather than 1, thus saving writes.

c2p or chunky to planar is any algorythm that takes a chuncky frame buffer and writes to a planar graphics arrangement. There are lots of ways to do it, and none are as fast as simply writing a chunky buffer. Because one chunky pixel has to be broken into bits and stored in each plane of the output.

In other words there is no hardware "magic" like with mode x on vga that makes it faster.

If you use 2 color (wireframe or pattern) graphics there is only one plane so it is as fast as chunky.

[KThunder]

Well, I don't mean to imply anything negative when I call it a "hack" - it's definitely a useful mode, if a bit difficult to wrap your head around at first. I just mean that it's not a planar mode in the usual sense, where the bits of a pixel are spread across multiple linear bitmaps - each pixel is contained in one byte, it's just that the bytes for consecutive pixels are strangely interleaved by the VGA's normal planar hardware.
 

Yes. Michael Abrash is a terrific writer, and his stuff is well worth the read even if you're never going to touch 80x86 programming or low-level EGA/VGA programming. His stuff did more to help me understand code optimization than anything else I'd read on the subject.

I didn't think anything bad when you said "hack" I just meant that it is such a feature that it works perfectly on every single IBM and compatible clone cards. IBM had bios modes that were a subset of what the vga chip could actually do, and the clone cards included it.

mode x also had "square" pixels so no scaling was neccisary before displaying graphics.

Its kind of like ham in a way, its not a normal method of graphics output but it has some excellent uses. Ham displayes more colors, Mode x is very fast. Ham may have been more designed into the hardware though.

[KThunder]

given isa bus limitations and ocs superiority joystick polling is integral to the discussion. If you send 15 megs over the bus in vga snoopdog mode and 10msec later poll the joystick port, you get flashed by the planar chick. Amiga has Paula (i dated a girl named paula once, nice girl, nicccely chunky:) ) and you can poll the port every nth nanosecond.

with or without popcorn!