Mandelbrot and Video

Like with the C64, this is probably the reason you came here:

The friggin’ fastest Mandelbrot displayed on a IIgs, ever! 😉

Yeah, you’re right, it’s not the fastest Mandelbrot calculated by an IIgs (its very own 65c816 CPU, that is)… but hey, it’s still kinda cool – and sooooo much faster!

Okey-Dokey, here we go, a complete Mandelbrot in 60s. This time in colorand zooming in! I couldn’t do that on the C64 as the C-Compiler didn’t natively support IEEE754 doubles (like Orca-C does) and having a mouse also helps a bit, too:

Wow, that was nice, wasn’t it?! (Sorry for the shaking, need to get a tripod soon)
Especially when you take in concern how ‘far’ the native 65c816 code got during the video on a ‘sped-up’ 10MHz TransWarp GS.

Like with the T2C64 version there are surely several things which could be improved, but the IIgs (even at native speed) is well capable to handle the little bit of extra work. The limiting factor is the bus-speed, i.e. how quick the Transputer can push his data into the host (IIgs). You can clearly see that by the time it took the display the 3 zooms: They all took about 60 seconds, even each zoom means more calculations as the iteration is doubled each zoom, in this case 32, 64, 128.
The Orca-C source/binary of this demo -and the previous AppleSoft sample- is available here (zip’ed PRODOS disk-image). It won’t make much sense without a T2A2 and is GS/OS-only as it uses QuickDraw II and the EventManager (for mouse & keyboard).

Final words: Don’t get too excited about the acceleration of the IIgs… it’s not accelerated at all. It’s more like a co-processor attached to it. And even then, you’ll need something really calculation-intensive to justify the time you’ll loose due to communication between the Apple and the Transputer. A single square-root for example wouldn’t make much sense.
But OTOH, that’s exactly things are handled with the Innovative Systems FPE (using a M68881). So it might be worth evaluating. Maybe I’ll write a SANE driver if I have the time to get a deeper understanding of GS/OS.

As my two targets (C64 & Apple II) are working now, I’m thinking about creating a ‘real PCB’ in the medium term. Given the rarity of the Link-Adaptor (Inmos C012) I’m currently looking into the possibility to use a larger CPLD to move the C012 into that. This would actually make this ‘project’ a product to buy.
But don’t hold your breath, need to get an eval kit first. Then some 100 days of fiddling, cursing and crying… and then more.

well, 6 years later it happened: The T2A2 became a proper PCB design… and got some additions too!

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