28 May 2024, 09:26 | #1 |
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Motorola's 68000 Series: Its Rise in Ten Computers
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 |
28 May 2024, 18:11 | #2 |
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I always find it somewhat sobering that the 68020 was launched one year before the Amiga...
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28 May 2024, 18:19 | #3 |
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28 May 2024, 19:20 | #4 |
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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). |
28 May 2024, 19:39 | #5 |
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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).
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28 May 2024, 20:05 | #6 | |||
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28 May 2024, 20:23 | #7 | |
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Before that people were attaching 68020 CPUs to the A1000. 68020 accelerator boards started appearing in 1986. |
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28 May 2024, 20:25 | #8 |
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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.
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28 May 2024, 20:48 | #9 | |
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The article mention the main contributor to the 68000 : Nick Tredennick
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Unfortunately he passed away 2 years ago and it was at Los Gatos! |
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28 May 2024, 20:49 | #10 |
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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 . |
28 May 2024, 20:53 | #11 | |||
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DTACK GROUNDED #35 - September 1984 Quote:
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02 June 2024, 01:11 | #12 |
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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
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02 June 2024, 10:32 | #13 |
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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?
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06 June 2024, 20:29 | #14 | |
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”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.. Last edited by eXeler0; 06 June 2024 at 20:37. |
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10 June 2024, 19:07 | #15 |
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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.
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10 June 2024, 19:31 | #16 |
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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.
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10 June 2024, 21:29 | #17 | |
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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) |
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10 June 2024, 22:21 | #18 | |
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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. |
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10 June 2024, 22:31 | #19 | |
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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...) |
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12 June 2024, 02:54 | #20 | |
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68020 is designed for UNIX Workstations costing 5-10x more than an A500 Doh! |
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