The No-CPU Amiga Demo Challenge
github.com
github.com
https://youtu.be/OXT5MrDdyB8?si=cZChImbAi3JBbFFl&t=49
This also gives me a bit more understanding of how the Video Toaster was possible to architect in a day with such slow CPU clock speeds. It seemed like magic at the time compared to limited capabilities of IBM PC clones. I hadn't realized how much capabilities these other Amiga chips provided.
If another non-genlockable computer could have generated the remapping addresses fast enough in those days, a Toaster-like device could have been designed to work with it. It just would have had to include a full separate genlock and the output would have been delayed a frame to allow that circuit time to work. So, it was possible, it just would have cost a bit more. How much more? Around that time, separate genlock cards capable of syncing up two disparate video sources sold for around $1,000.
On the other hand, an interactive, real-time address generator capable of keeping up with full video speeds would have cost tens of thousands of dollars. For example, the Quantel Mirage cost $700,000 in the 1980s and didn't even generate its addresses in real-time. The Mirage pre-rendered all the remapping addresses to a massive RAM disk using a Pascal program running on a workstation (which could take an hour or more) and only played them back on cue. The real-time part of the Mirage's hardware just digitized live video input and mapped it to the fixed stream of pre-generated addresses. Thus the Mirage could apply complex effects to live video but the effect geometry had to be canned, not interactive. The Ampex Digital Optics hardware did generate addresses in real-time entirely in logic-gate based hardware. Take a look at the ADO patent to gain an appreciation for just how insanely hard it was for 1980s era pre-GPU hardware to generate addresses at broadcast video rates. (https://patents.google.com/patent/US4472732/en) In fact, these esoteric real-time broadcast video effects systems were some of the first steps toward GPUs. According to Ken Kutaragi, Sony's $350,000 System-G 3D video effects hardware (which reportedly had worldwide sales of... three units) led to the Playstation GPU.
The Toaster effects could be interactive because it relied on the Amiga's graphics output as its address generator. In fact, the Amiga computer's monitor output was normally used to display the Toaster user interface but when a video effect was running the interface was entirely replaced with odd patterns that looked like bar codes. These were the addresses being generated by the Amiga custom chips and fed from the Amiga to the Toaster hardware in real-time via the monitor output (technically the fastest 'bus' in the system). This was a remarkable hack which required the Toaster to be very tightly coupled with the Amiga's hardware design and also involved some other extremely clever trade-offs. Relying on the Amiga's graphics output as the real-time address generator enabled the Toaster to exist and was also why the Toaster could never be ported to another computer or even to the PAL video standard. The Amiga's genlockability just allowed the Toaster to be even less expensive.
No way, that’s why the wipes took over the switcher screen and where that peculiar vertical line pattern came from?
I can still remember these with an odd intensity from playing with the Toaster at the studio where my dad worked 30 years ago.
I'll never forget seeing a group of Japanese engineers from Sony who designed high-end video effects hardware (which cost >20x what a Toaster system did) seeing the Toaster at the NAB trade show for the first time. There was nothing but stunned silence and shocked looks... then after a long while of watching the demo and seeing the interface turn into weird garbage during each effect, you could see the light dawn on their faces - and then the whole group erupted into excited, highly-animated chatter. I've never wished I spoke Japanese as much as that moment :-).
Trivia: He's the brother of Dana Carvey, and Garth wears a Video Toaster T-Shirt in Wayne's World 2.
Even the CGA card of an IBM PC could have been modified in this way. I can imagine a hack where the flash attribute in text mode gets used to act as the overlay key, but it would have been pretty darned ugly.
Of course the very thing made genlock work so well on the Amiga (the use of bitplanes) was a factor in the ultimate demise of the Amiga in the 1990s. It's funny how the memory bandwidth tradeoff changes things.
The blitter is another coprocessor with a different set of limited features. Blitter as a generic term refers to a piece of hardware that can copy memory from one location to another without CPU involvement, but the Amiga blitter is more full featured than that. It also has the ability to render lines, fill areas of the screen, and apply shifts and masks to data rather than just copying it. Of course, when I say "render lines" or "fill areas of the screen", what I actually mean is that it can write specific patterns to regions of memory - there's no actual requirement that they be on screen at the time.
A really important thing here is that while the copper can't write to memory itself, it can configure the blitter, and the blitter can then modify memory. One fun thing here is that there's absolutely nothing stopping you from using the blitter to modify the code that the copper is executing.
The naive implementation of a no-cpu demo would simply be to load all the assets into RAM and then have the copper reprogram the custom chips to display them and play audio. But combining the copper and the blitter gives a turing complete execution environment that ought to be able to do almost anything you could do with the CPU (the blitter can't touch hardware registers so you're still limited to whatever registers the copper can access, and you can only access the RAM the custom chips have access to, not the larger range of fast RAM), just somewhat more slowly.
It would also be used to support double-buffering for displaying smooth videos or other moving graphics - you'd have the two buffers, and the copper would change which one was being displayed while the scan was in the flyback period between frames.
I'd have loved to live through 10 years of the Commodore 64, 10 years of the Amiga, 10 years of the NES, 10 years of the SNES...
only if we got more Heretic/Hexenlikes too!
… Ya know, I think Doom may have actually been a parallel-universe/built-by-aliens type of fluke: It seriously accelerated gaming and the social perception of gaming, and in turn pushed computer technology adoption towards 3D cards (and everything else required to support them) much faster than it may have happened without Doom.
So I think if certain "killer apps" weren't released when they did, then maybe people might have been fine with tech chugging along at a more relaxed pace..
and iddqd costs ten bucks to unlock, but it's part of a lootbox with all the other cheat codes in it
Back in "those days" you could literally count the extra colors you would get to see on the screen after each new generation!
I made a "Star Wars" scrolltext once, on a so-called "bazaar" screen with other effects... but it was on ST, kind of challenging ;) I still have the floppy disk in a box, but I'm afraid it's been demagnetised like the others over time (~35 years ago).
This machine now has more problems with flaky IC connections and wonky caps than disks. Given the visual glitches in some of my old DeluxePaint files viewed on the actual machine, I'm surprised the circuits didn't mess up any of the transfers, because I didn't get the glitches in the emulator afterwards..
Data can probably still be read. Especially if the floppies are DD. Don't wait for it to become unreadable. Backup now rather than later.
Interesting parallels with GPUs too.
what are these not-CPU chips even capable of?
Alice, Lisa, Paula were some of the chips that made the Amiga the Amiga.