Difference Between A CD32 and An Amiga 1200?

[Heavy Stylus]

Hi there - the answer to this question may not be as obvious as suggested by the title...

Whilst creating some unofficial CD32 ports of games I've found one particular game that is causing me a real headache - http://aminet.net/package/game/race/LastLap

Now, this runs fine on an unexpanded A1200, but for some reason it plays at nearly double speed on an unexpanded CD32! What the hell is causing this? I assumed that the two machines were based on the same hardware, but is the CD32 actually faster?!

Both machines are PAL.

[Graham Humphrey]

Other than a different Kickstart and the Akiko chip I though the CD32 was the same hardware-wise to the A1200? So that is a bit odd, unless it's heavy on the ol' chunky to planar conversion routines

(Not that I know what that actually means...)

[alexh]

Titles had to be written to use Akiko.

It's going to be something stoopid like the ROM/RAM is slower and so it cannot render in 50fps and so it misses a VBL which doubles the speed of the game or something...

[Steve]

The CD32 has special go-faster stripes located underneath the machine.

[prowler]

Originally Posted by Steve

The CD32 has special go-faster stripes located underneath the machine.

No, they're the ventilation slots!

[Paul_s]

The CD32 was painted using bristles from David Pleasance's beard making it almost as unique as Chuck Norris's beard.

[Heavy Stylus]

Hey - no worries, I've decided against using the game anyway. Thanks for the help, I'll keep an eye out for other games that act up in the same (weird) way

[Heavy Stylus]

Just out of interest though... what does the akiko chip do?

[Paul_s]

Originally Posted by Heavy Stylus

Just out of interest though... what does the akiko chip do?

Does chunky to planar conversion and also handles some of the controls for the cd-rom device apparently...

[Heavy Stylus]

Does this mean that a CD32 is better at running games like Gloom than an A1200? What does chunky to planar conversion actually mean, and did many CD32 games actually use the chip?

[TCD]

This explains it rather nicely : http://oldwww.nvg.ntnu.no/amiga/amig...igaFAQ_16.html

[Amiga1992]

Originally Posted by Heavy Stylus

Does this mean that a CD32 is better at running games like Gloom than an A1200?

Not if the game does NOT use the chip. It won't step in unless it's programmed with Akiko in mind

What does chunky to planar conversion actually mean

Originally Posted by The Amiga FAQ, by Ignaz Kellerer

3.1 What are chunky and planar displays?

    

   Simply put, the terms `chunky' and `planar' (short for `bitplanar')
refer to different ways of storing graphics information in a computer's
memory. They are rather easy to understand, as far as things go, but
incredibly difficult to explain:



   Computer images are arranged as a grid of pixels, each of which can
be thought of as a number representing the color number of the pixel,
sort of like a paint-by-numbers scheme.  For example, here's a
simplified example image, in four colors:



        00302132



   The Amiga stores this image in a `bitplane' mode. That is, it is
represented by several planes of bits (binary digits, 1s or 0s). This
is a four-color image, so each color number could be represented by two
bits.  Therefore there are two bitplanes:



        00100110    Here's bitplane 0
        00101011    And here's bitplane 1
        --------    Now, let's add them up, binary style:
        00302132



   Which is the final image. If the image was in two dimensions, it
would truly be composed of bit planes. However, I'd need three
dimensions to show multiple bitplanes overlayed, and therefore for
simplicity we're working in one dimension (which is all we need).



   Now, there's another way of storing this image.  How about if we
localize the bit data in little chunks?



        00 00 11 00 01 10 11 01 = 00302132



   This is the principle of the `chunky' pixel mode.



   Both methods of image storage are perfectly logical, and no one can
say that one is better than the other. However, there are certain
technical aspects which cause certain advantages and disadvantages.

The rest here: http://stason.org/TULARC/pc/amiga/fa...-displays.html


edit: damn you TCD!

[alexh]

C2P is as it sounds it converts a chunky screen memory into planar using multiple mem copies etc.

The 68EC020 in the A1200 when used with FastRAM is faster than the Akiko.
The Akiko is faster than a 68EC020 when used with ChipRAM (which is all the CD32 has).

I think the philosophy of putting the C2P in the Akiko was :

RAM is VERY expensive, the CD32 probably won't have any Fast RAM. We're designing a CD controller chip anyhow. Why not "bung it in"?

[TCD]

Originally Posted by Akira

edit: damn you TCD!

Hi there Akira
Didn't know about the Akiko myself until today, so thanks for that Graham and the rest of the bunch

[Heavy Stylus]

Yes - thanks guys! You learn a new thing every day

So, do any games actually use this chip?

[alexh]

Wing Commander CD32, MooVid and I think that's it? Toni Wilen will know for sure.

[Amiga1992]

Can Wing Commander CD32 be "hacked" somehow to use FastRAM instead?

[StevenJGore]

Wing Commander CD32, MooVid and I think that's it?

Microcosm uses it too, I believe.

[alexh]

Microcosm doesn't use Akiko

[musashi5150]

Games don't have to be programmed to use the Akiko if they rely on OS functions like WriteChunkyPixels() to draw the display. From KS3.1+ if there is C2P hardware available (i.e. Akiko) the OS will use it automatically. But it's unlikely that any CD32 games used proper chunky displays anyway.

I know you can write you own C2P conversion code for Gloom Deluxe. This package, for example, includes an Akiko C2P module http://aminet.net/package/game/demo/GloomC2P10