Motorola's 68000 Series: Its Rise in Ten Computers

[TEG]

Someone wrote an article about the 68000 and the computers it powered. Interesting to know about its origins.



https://thechipletter.substack.com/p...es-its-rise-in

[TCD]

I always find it somewhat sobering that the 68020 was launched one year before the Amiga...

[TEG]

Originally Posted by TCD

I always find it somewhat sobering that the 68020 was launched one year before the Amiga...

Yeah, I guess the price was not the same but we might have expected an Amiga 68020 motherboard option in 1987.

[Megalomaniac]

How much would using the 68020 (or 010) have added to the A1000's cost in 1985, or the A500's in 1987? Using an 020 would also have presumably limited how much code could have been ST-ported (I assume an ST with an 020 or 030 has compatibility issues comparable to the A1200?).

If the 020 had been used in the A500 but not the A1000, you'd need some sort of boot options to at least disable the cache, otherwise a huge percentage of early Amiga games wouldnt've worked on it. That would have been a far higher proportion than when the A1200 launched, because by 1992 the 020 and higher were widely in use, and the A3000 was already out (games released after the A3000 seemed to have a higher chance of working on the A1200).

[TCD]

Originally Posted by Megalomaniac

If the 020 had been used in the A500 but not the A1000, you'd need some sort of boot options to at least disable the cache, otherwise a huge percentage of early Amiga games wouldnt've worked on it.

To be fair there's about a handful of titles before the Amiga 500 launch worth playing and I don't think it would have made a huge dent in the success of the machine if those titles wouldn't have worked (properly).

[TEG]

Originally Posted by Megalomaniac

How much would using the 68020 (or 010) have added to the A1000's cost in 1985, or the A500's in 1987? Using an 020 would also have presumably limited how much code could have been ST-ported (I assume an ST with an 020 or 030 has compatibility issues comparable to the A1200?). If the 020 had been used in the A500 but not the A1000, you'd need some sort of boot options to at least disable the cache, otherwise a huge percentage of early Amiga games wouldnt've worked on it. That would have been a far higher proportion than when the A1200 launched, because by 1992 the 020 and higher were widely in use, and the A3000 was already out (games released after the A3000 seemed to have a higher chance of working on the A1200).

I agree, I was thinking about another reference to the Amiga family, an "A2020" or eventually directly the A2000 with the 68020 if not too much complicated to develop. Would have show that the brand was keeping up with the tech. And the 68020 was supporting the 68851 MMU. So an "Amiga A2020M" would have been an option to professionalize Amiga OS ie to redesign it to manage MMU.

Originally Posted by TCD

To be fair there's about a handful of titles before the Amiga 500 launch worth playing and I don't think it would have made a huge dent in the success of the machine if those titles wouldn't have worked (properly).

Yeah but the price of the 68020 was too high and there was production problems. So the 68000 for the A500 was the good option.

A great debate broke out about how to refer to the underlying design of the new chip in marketing materials. Technically, the 020 was moving from the long-established NMOS logic design to a CMOS layout, which requires two transistors per gate. Common knowledge of the era suggested that CMOS cost four times as much as NMOS, and there was a significant amount of the market that believed "CMOS equals bad.The design was completed in the summer of 1983 and announced in June 1984. This "super chip" was significant news at the time, with the New York Times making it a lead story in their business section. The launch price was quoted at $487 each, about the same as the 68000 when it was launched in 1980, but the 68000 was now available for about $15. However, it was understood that it would be some time before computers using the new chip would be available, as existing designs would have to be heavily modified to take advantage of its performance.
https://en.wikipedia.org/wiki/Motorola_68020

[Bruce Abbott]

Originally Posted by TEG

Yeah, I guess the price was not the same but we might have expected an Amiga 68020 motherboard option in 1987.

We got an Amiga with 68020 in 1988. MMU and FPU too! And 4MB of 32 bit RAM. A friend of mine had one.

Before that people were attaching 68020 CPUs to the A1000. 68020 accelerator boards started appearing in 1986.

[Thomas Richter]

Originally Posted by TCD

I always find it somewhat sobering that the 68020 was launched one year before the Amiga...

We had a couple of 68020 based hp workstations around 1990 at the university, 8MB memory, continuously swapping if running X. For a home computer, the 68020 was way, way, way out of reach at this time.

[TEG]

The article mention the main contributor to the 68000 : Nick Tredennick

Much of the logic design of the 68000 would be done by Nick Tredennick:

Nick probably brought the most amount of intelligence to the project. He actually helped us design in detail many of the integral parts. This was the first microcoded designed microprocessor that I can find any little history of. He did almost all of the microcode.

I see Nick have a Wikipedia page: https://en.wikipedia.org/wiki/Nick_Tredennick

Unfortunately he passed away 2 years ago and it was at Los Gatos!

[Megalomaniac]

The early Amiga games weren't great compared to Amiga games from its heyday, but they were great compared to existing C64 / Spectrum / in some cases ST games, so it would have been awkward to launch the A500 with an 020. Faery Tale Adventure comes to mind as one that fails on an 020, which was adored at the time. I'm assuming the cost would have been prohibitive for the A500 anyway, considering that in the UK at £500 on launch in late 1987 it was already £200 more than you could get an ST for?

How much would it have cost to launch the A2000 with an 020 instead of a 000 in 1987? You could ignore a few games incompatibilities .

[Bruce Abbott]

Originally Posted by TCD

I always find it somewhat sobering that the 68020 was launched one year before the Amiga...

Not quite.

DTACK GROUNDED #35 - September 1984

So the 68020, which now exists and which will be sampled in about four months and will be in production in a year...

DTACK GROUNDED #41 - May 1985

We have had two prototype 68020s which run (with a bug list, true) at 12.5MHz for four months now. Sample 12.5MHz 68881 math chips are available. Both the 68020 and the 68881 are built with 2 micron CMOS technology and no one that we know of doubts that Motorola will be able to produce 16MHz (actually 16.67MHz - the clock period is specified as an even 60 nsec) parts in due time, meaning in a year or less.

[Cris1997XX]

Launching the Amiga 1000/500 with a 68020 would've been incredibly expensive, if not even a little useless for consumers back then. I think a better and cheaper option would've been a 10MHz 68K, alongside a small pool of fastRAM to speed up operations

[Megalomaniac]

I think there were technical reasons to do with chipset timings as to why the 68000 Amigas ran at just over 7Mhz rather than the 8Mhz of the ST? Whether FastRAM would have made enough difference to performance is debatable?

[eXeler0]

Originally Posted by Megalomaniac

I think there were technical reasons to do with chipset timings as to why the 68000 Amigas ran at just over 7Mhz rather than the 8Mhz of the ST? Whether FastRAM would have made enough difference to performance is debatable?

”The bot” explains it like this:
8><————-
The PAL Amiga ran at 7.09 MHz because PAL television systems in Europe operated at a 50 Hz refresh rate with 625 lines per frame. This required a clock frequency that could handle these timings, leading to the 7.09 MHz figure, which is derived from the color subcarrier frequency of 4.43 MHz multiplied by 1.6.

On the other hand, NTSC Amigas in North America ran at 7.16 MHz to match the NTSC television system’s 60 Hz refresh rate and 525 lines per frame. The NTSC standard used a color subcarrier frequency of 3.58 MHz, and the clock frequency for the Amiga was calculated by multiplying this by 2.

In essence, these clock speeds ensured that the Amiga’s video output was in perfect sync with the television standards of their respective regions, making sure your games and graphics looked as smooth as possible, regardless of where you were playing them.
——————><8

If you think the NTSC numer 3.58MHz sounds familiar, look at the CPU speed of the Super Nintendo ;-) and 3.58 / 2 = NES CPU (1.79MHz) So it wasn't just the Amiga..

[Megalomaniac]

That's not quite what I was alluding to - I was talking about the ST running the same processor at a slightly higher clock speed than the Amiga (and I think where we have 14.28Mhz A1200s they had 16Mhz processors too?) My understanding is that the custom chips couldn't run with the slightly faster processor speed, for technical reasons which are probably beyond me.

[Thomas Richter]

Originally Posted by Megalomaniac

My understanding is that the custom chips couldn't run with the slightly faster processor speed, for technical reasons which are probably beyond me.

The technical reasons were given. The Amiga was designed to drive TVs, originally. The ST was designed for a monitor, so the frequencies did not matter.

[Entelodon]

Originally Posted by Megalomaniac

My understanding is that the custom chips couldn't run with the slightly faster processor speed, for technical reasons which are probably beyond me.

It was common to synchronize the CPU and graphics chip with the TV signal when computers and video games were connected to TVs.

The CPU of an NTSC Super NES runs at 3.58 MHz which is 1x the NTSC signal
The CPU of an NTSC Atari VCS runs at 1.19 MHz which is 0.33x the NTSC signal
The CPU of an IBM PC runs at 4.77 MHz which is 1.33x the NTSC signal (CGA has a composite mode)

[Bruce Abbott]

Originally Posted by Thomas Richter

The technical reasons were given. The Amiga was designed to drive TVs, originally. The ST was designed for a monitor, so the frequencies did not matter.

To be precise, the Amiga was originally designed to output pixels in sync with the 3.579545 MHz NTSC chrominance subcarrier, enabling the creation of "artifact colors" like the Apple II and IBM PC did (which is why the PC ran at 4.77MHz).

Many other home computers used a similar technique, but even those that didn't sometimes used a 'non-standard' clock frequency to get more accurate video timing. This also applies to the ST!

Master clock frequencies of various ST models:-
32.0424 MHz NTSC ST (non STe)
32.04245 MHz NTSC Mega ST
32.084988 MHz All PAL computers.
32.215905 MHz NSTC STe/MEGA STe

The ST's CPU clock is derived from the master clock by dividing it by 4, which means the CPU is actually not running at 8 MHz, but slightly faster.

[Gorf]

Originally Posted by Megalomaniac

How much would using the 68020 (or 010) have added to the A1000's cost in 1985, or the A500's in 1987?

Other variants would have been possible, since there were a lot of second source 68k professors out there in the 80s:

Rockwell (R68000)
Signetics (SCN68000)
Mostek (MK68000)

and of course the Hitachi (HD68000) produced in 2.7 um structures allowing up to 12.5 MHz. (used in the X68000 at 10MHz, as the DRAM speed would be the bottleneck at the time...)

[CCCP alert]

Originally Posted by TCD

To be fair there's about a handful of titles before the Amiga 500 launch worth playing and I don't think it would have made a huge dent in the success of the machine if those titles wouldn't have worked (properly).

And only a handful after KS 1.2---->KS 1.3 era too lol

68020 is designed for UNIX Workstations costing 5-10x more than an A500 Doh!