-The real Atari 8bit Computer Successor

kool kitty89 · February 27, 2018

You can find a lot of Amiga history online. Jay Miner and other Atari engineers were unhappy that Atari (under Warner) didn't want to invest in a 16-bit computer and they left. In the end, Commodore ended up with the Amiga and Jack Tramiel had engineers working on what would become the ST after he was kicked out of Commodore. So, yes, the Amiga largely came from ex-Atari people and Atari was under ex-Commodore management. It was a very bizarre turn of events.

This is a quick synposis:

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

I haven't read the whole thread to see if Curt or Marty or some other historians on the site already corrected this, but Warner-Atari heavily invested in the Amiga chipset and had licensed it, planning it as a home computer, arcade machine, and game console (codenamed MICKY). They also had several in-house 16-bit (68000, x86, and maybe 16032/32016: I think Trammel Technologies dabbled with the latter before switching to the 68k).

Amiga ended up cheating out of their contracts with all licensees, and at least in Atari Inc's case, illegally 'refunding' the investments made while claiming to have failed to produce working silicon. Meanwhile they'd signed an exclusive agreement with Commodore. With the confusion going on in June/July of 1984 at Atari Inc, and Warner's horrifically managed liquidation of the company without notifying executives (especially Atari President James Morgan) led to that slipping through the cracks and some lower level management accepting Amiga Inc's refund check without reading over the contract properly. (it's that same sloppiness that led to Tramiel's poor reputation and the myth that he 'fired everyone' when taking over ... rather than the reality that Atari Inc was liquidated, the arcade business spun off and home/consumer business's assets sold off ... it's also that mess that led to some of the neat in-house designs, hardware and documentation along with engineers walking off or becoming fragmented)

It was also that breach of contract that leveraged Atari Corp's later settlement with CBM over the ST lawsuit. (the Amiga contract was brought in to counter-sue them)

Incidentally, the Amiga contract allowed a game console/arcade machine to be released in 1984, a computer in 1985 with no more than 128kB of RAM, and unlimited hardware configurations from 1986 on. (had Tramiel gotten hold of that license, I imagine they'd have made do with 128k and perhaps shipped without GEM initially, just the text based portion of TOS, and also probably been forced to include RAM expansion via slots or DIP sockets and possibly even use an external cart slot for the OS ROMs ... or slave the cart slot to that purpose while abandoning any intent to use ROM cart based software: though using internal ROM sockets and intending service centers to install OS ROMs as they arrived may have been the more natural decision)

The ST was originally intended to have a 128k (130ST) as the bottom-end model, of course, but was abandoned as RAM prices fell and the OS became too large. (and a cut-down version without a DOS at all and just BASIC and tape drive interface routines became unappealing)

On the note of the actual thread topic, though: why not add MARIA to the 8-bit chipset?

This is something that came to mind while I was looking at the flaws and problems (and possible fixes) for what made the Panther problematic a few years later, but in any case:

Replace FREDDIE and possibly the MMU with a new gate array ASIC, performing the memory mapping and DRAM controller duties and fast enough to allow Amiga speed bus cycles (280 ns cycles) fast enough to service existing ANTIC and SALLY access times while only using 50% of the bus cycles, but rather than fiddling with ANTIC or SALLY timing at all (or trying to spin off 3.58 MHz 6502s or what not) use that added bandwidth in leu of cart ROM access for MARIA graphics data, and use the new mapper/controller chip to interleave things seamlessly to avoid the need for CPU halts during MARIA DMA. (though you'd still need to wait for vblank to do MARIA register updates and list/pointer updates in SRAM)

Bump MARIA SRAM up to 8kB (a single 8kB SRAM, cheaper, less board space, etc ... 32k would be nice, but not really needed given you're pulling most graphics data from DRAM).

Probably map the normal 48k MARIA cart ROM space directly into A8 space and put MARIA registers and SRAM onto the 16k bank switched segment.

Possibly add the ability to enable/disable either of the 8k cart ROM chunks to allow the full 64kB of DRAM to be used and those 8k banks flipped in as needed. (I forget if the player 3 and 4 GTIA trigger inputs were used already, but those might be handy for using an additional 2-bits of bank select control) You'd still need on-cart bank-switching logic to extend beyond 16k as well, but you'd make the most of RAM this way and avoid the issue of MARIA/A8 DMA conflicts in ROM. (cheap ROM being too slow to interleave in, at least when both ANTIC/SALLY and MARIA are trying to access it)

You'd thus have a really nice system with MARIA graphics operating without holey DMA and genlocked over GTIA graphics (MARIA was designed with this in mind for the planned laserdisc expansion, so genlock with GTIA should be quite possible, particularly as all would be running off a synchronized clock and using common color/pixel clock times or integer multiples of those: ie if one was using 320 pixel and the other 160 pixel modes). MARIA allows for up to 4-bit pixels in its objects, which could potentially also allow a 12-color linear bitmap screen overlay on top of ANTIC+GTIA character or bitmap modes, or turn off the latter entirely for 100% CPU time in a 12-color bitmap. (or 13 colors given GTIA's background color should still be available)

For typical late 80s console/arcade games, I imagine it'd be appealing to use 3 or 12 color MARIA sprites over a 5-color ANTIC character scroll layer with GTIA sprited used for a bit of added color. (so 12 color sprite layer + 9 color background)

Doing proper Genlock would also give nicer video output than the 7800's hacked solution of merging TIA and MARIA video lines. (a simple disconnector switch also solves that, of course)

Further, this sort of machine would have been a much more potent game console to release for 1987 than the XEGS, while also better meriting the price points the XEGS was initially sold for (substantially more than the $99.99 65XE or $89.99 7800 and of course $49.99 for the 2600Jr). The deluxe package XEGS with light gun and keyboard originally retailed for $199.99, and I rather doubt the added MARIA+SRAM + Gate Array chip and 150 ns DRAM rather than old 200/250 ns stock would've pushed it even that high. (probably more like $150 in a basic set and $200 with keyboard and games and/or possibly other software)

https://youtu.be/2N2BUTIpnDI?t=97

Plus you'd have a game machine with substantially greater advantages over the NES and Master System. (still some trade-offs like the lower resolution for most purposes, but a monster sprite engine for the time and some pretty nice colors all around ... and the flexibility to do some nice software rendered effects to a linear framebuffer and a ton of RAM for a console at the time, and chunky pixel graphics, so very well suited to storing compressed data on cart to save space)

You'd also have a lot more CPU time to do complex POKEY modulation effects (or 4-bit PCM) or possibly make some use of the GTIA beeper channel. (though that would probably be more useful if you added GTIA beeper control to the new ASIC, maybe slaving it to some neat PWM sound ... possibly even useful for sample playback, but I'm mostly just thinking fixed-volume variable duty cycle pulse wave stuff ... though slaving it as a PWM DAC would certainly be interesting, I'm not sure what sort of resolution you'd get out of it: if you could toggle at at 7.16 MHz, that'd allow 28 kHz 8-bit sample playback, which would be quite neat, especially if it was DMA loaded ... though a CPU-loaded FIFO would be pretty good, too)

You could obviously have a 128 kB variant of that on the computer end of things, but a game console would probably be better to stick with 64k. (you could drop lower, but that would hamper the compatibility and selling point for promoting expanded A8 development in general as a computing platform on top of enhanced game machine, plus 64kx4-bit DRAMs were a very economical density at the time and using 2 or 4 16kx4-bit ones for a 16 or 32k system would seem a poor value by comparison)

And, of course, such a game console would squarely sit in the Home Computer category as far as Nintendo's predatory licensing was concerned, and would soundly avoid the sort of problems the 7800 and Master System both suffered from.

Edit: you could also use that faster DRAM timing to allow for a 3.58 MHz 6502, but I'm not sure existing (even new production 1987) NMOS SALLY chips would tolerate that well enough, and 65C02s were around, but then you had to deal with RDY rather than HALT among other things (short of making a CMOS SALLY). OTOH, using that 7.16 MHz bus/DRAM controller ASIC clock divided by 3, you'd get a more likely SALLY-tolerant 2.39 MHz, which would be a nice speed boost for some things, and still wouldn't change ANTIC timing. (just more wait states for SALLY when overlapping with MARIA DMA cycles) 3.58 MHz would obviously be nicer, though. (even more wait states for MARIA, but still a speed gain, and faster interrupt response)

You'd need normal 1.79 MHz modes for full compatibility. (also standard XL/XE memory map modes, possibly disabling the cart-slot banking if that proved problematic)

Wait: RDY in the 65C02 behaves like HALT on SALLY, doesn't it, since it's CMOS and static and thus needs no refresh? So you could use a 65C02 in there without problem, and use 3 or 4 MHz rated chips at 3.58 MHz. (unless there's any software using undocumented NMOS-specific opcodes or such, you shouldn't have compatibility issues ... plus you get the enhanced instructions, some more than others depending which 'C02 variant they used ... probably Rockwell though, given Atari Corp was using them a fair bit already for chip vending)

That aside from other hypotheticals, like if Atari had taken Synertek's assets when Honeywell liquidated. (Synertek was in trouble with Superfund cleanup/lawsuit issues, so it would've been on favorable terms, though another risk/reward investment for Tramiel to make like he did with Atari Inc's assets, though it was sold off in 1985, when Atari Corp was already pretty deep in investment debt)

Synertek had already been manufacturing 65C02s prior to being shuttered, for what that's worth, along with second-sourcing a bunch of Atari's custom chips, so it would've been a solid fit all-around. (albeit slightly moreso had the ST used more MOS chips for its 8-bit serial and I/O stuff rather than Motorola ones)

And why use a gate array for the new ASIC? It'd be much faster for testing/prototyping than a full custom chip (especially without an in-house chip fab) and would be much lower risk to produce at low volumes, hedging their bets on a potential flop. (if it really took off, they could probably spin off a full custom or standard cell ASIC to not only replace it, but embed the DRAM controller+MMU+CPU+ANTIC+GTIA+MARIA+POKEY+PIA all on one dense CMOS ASIC with a single 8-bit I/O bus and 16-bit plus bank-selected address bus, making it a solid budget console/computer platform around 1989 into the early 90s and also making a nice platform to cross-develop Lynx games for) You could also switch to a single 128kx8-bit DRAM chip by 1990/91 and discontinue the 64k models entirely.

It's worth noting that plenty of manufacturers stuck with gate arrays throughout platforms lives in spite of high volume production, so that's always an option too. (and you didn't need the raw logic speed that standard cell and full custom CMOS parts were doing in the late 80s ... Standard Cell also might not have been very widely used yet) Sega used lots of Gate Array chips for various things in the arcade and home consoles. (and the custom graphics/interface chip of the Sega CD was simply called the Gate Array in most documentation/programming literature) Flare Technologies also used Gate Array chips for their Slipstream hardware (the Jaguar was Standard Cell, though), which makes plenty of sense given they'd come from Sinclair, who'd used some of the pioneering Gate Array (ULA) production for the ZX-81 and Speccy.

Edited February 27, 2018 by kool kitty89

Bryan · February 27, 2018

Adding Maria is difficult because it needs to be the DMA controller and it cannot use DRAM. However, some of Maria's ideas could have been used in a successor to Antic.

Nebulon · March 1, 2018

Amiga ended up cheating out of their contracts with all licensees, and at least in Atari Inc's case, illegally 'refunding' the investments made while claiming to have failed to produce working silicon. Meanwhile they'd signed an exclusive agreement with Commodore.

According to the book "Commodore: The Amiga Years", nothing strictly illegal took place since there was only a letter of intent and an interim loan agreement (no signed licencing contract). You might want to take a look at pages 167,68 and 179,80. More information on the negotiations between Amiga and Atari are on pages 141 with mention that Atari 'altered the deal' (page 142). Stipulated in the loan agreement was an 'out' with the option to pay back the loan before a specific date. Morse exercised that right -- although there's even more to it than that (i.e. the bit about the chipset "not working")...

Even with Amiga backing out of the deal, Atari still benefited from extensive engineering meetings between Amiga engineers and Atari engineers regarding the Amiga chipset's design.

https://www.amazon.com/Commodore-Amiga-Years-Brian-Bagnall/dp/0994031025/ref=sr_1_1?ie=UTF8&qid=1519868495&sr=8-1&keywords=commodore+the+amiga+years

Nebulon · June 3, 2021

After helping to edit two books on the history of the Amiga and digging through a ton of info from people like Joe Decuir, I can unequivocally say that the Amiga is indeed the successor to the Atari 800. It was the reason why Joe and Jay left Atari in the first place. Joe had completed the rough block diagram of what would become the Amiga back in 1982. Supporting information follows:

https://www.youtube.com/watch?v=6YqDOKXQk1w
https://www.youtube.com/watch?v=1DnLmEaIhpQ&list=PLOT5j3ELi5BY9abqksYqI4U9ZH07bOtIV
http://www.blitter.com/~nebulous/amiga-articles.html