Comment by einr
1 day ago
The DX/2 66 is a true legend of a chip. It was so good. The final nail in the coffin for the Amiga and for 68k. I love the Amiga, but it just didn’t Doom.
Before it, you could claim that a 68040 was kinda-sorta keeping up with the 486 and that the nicer design and better operating systems of other computers made up for the delta in raw performance, but the DX/2 66 running Doom was the final piece of proof that the worse-is-better approach of using raw CPU grunt to blast pixels at screen memory instead of relying on clever custom circuitry was winning.
Faced with overwhelming evidence, everyone sold their Amiga 1200s and jumped ship to that hated Wintel platform.
I remember arguments (and benchmarks) around all the variations of the 486 since the bus speed/clock speed was uncoupled (the /2 is clock doubling). For some applications, a 50Mhz 486 with a 50Mhz bus would beat a DX/2 66Mhz with a 33Mhz bus.
And sometimes the DX/4 100Mhz would be slowest of all those at 25Mhz bus.
Nearly correct. The DX/4 100MHz had a 33MHz bus. The DX/4 75MHz had the 25MHz bus. I remember well because I had both.
Now I remember being annoyed that it wasn't the DX/3 as it should have been!
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I remember being so excited when I figured out how to jumper my DX/4 100 and operate it with clock doubling and a 50 MHz front side bus speed. Same core speed, faster memory and I/O.
My peripherals seemed to take it. My graphics output showed some slight glitches, which I was OK with for the speed.
However, I think it was a bit unstable and would fail a correctness challenge like compiling XFree86 or the Linux kernel, which were like overnight long runs. Must have been some bit flips in there occasionally. I seem to recall that once that reality settled into my brain, I went back to the clock tripler config.
I still remember scribbling on Athlons with a pencil to max them out - we probably spent as much on heatsinks as we saved on CPUs.
As I noted in my other comment (1), in 1985 Amiga OCS bitplane graphics (separate each bits of a pixel index into separate areas) was a huge boon in 2d capability since it lowered bandwidth to 6/8ths but made 3d rendering a major pain in the ass.
The Aga chipset of the 1200/4000 stupidly only added 2 more bitplanes. The CD32 chip actually had byte-per-pixel (chunky) graphics modes but the omission from the 1200 was fatal.
Reading in hindsight there was probably too many structural issues for Commodore to remain competitive anyhow, but an alt-history where they would've seen the needs for 3d rendering is tantalizing.
1: https://news.ycombinator.com/item?id=47717334
> The Aga chipset of the 1200/4000 stupidly only added 2 more bitplanes. The CD32 chip actually had byte-per-pixel (chunky) graphics modes but the omission from the 1200 was fatal.
The intention was good, but the Akiko chip was functionally almost useless. It was soon surpassed by CPU chunky to planar algorithms. I don't think it was ever even used in any serious way by any released games (though it might have been used to help with FMV).
Ah, I was under the impression that it had a native chunky mode but it was a built-in C2P routine? Anyhow, seems it was useful (1) when running on stock CD32's but not in conjunction with faster machines.
1: https://forum.amiga.org/index.php?topic=51616.msg544232#msg5...
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The CD32 chip actually had byte-per-pixel (chunky) graphics modes but the omission from the 1200 was fatal.
I agree. Unfortunately, even with chunky graphics and/or 3D foresight, 68k would still have been a dead end and Commodore would still have been mismanaged into death. It’s fun to dream though…
Was it necessarily a dead end? Considering the ways Intel and later AMD managed to upgrade/re-invent x86 that until x64 still retained so much of the x86 instruction encoding/heritage (heck, even x64 retains some of the instruction encoding characteristics).
Had the Amiga retained relevance for longer and without a push for PowerPC I don't see a reason why 68k wouldn't have been extended. Heck the FPGA Apollo 68080 would've matched end of 1990s P-II's and FPGA's aren't speed monsters to begin with.
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There were no tech problems IMHO, it was all mgmt problems. They could have chosen a handful of completely different (edit: mutually exclusive even!) tech paths and still have won, but instead they chose to do almost nothing except bleeding the company dry.
Edit: I don't mean that their success was certain if they executed better. I mean they did almost nothing and got the guaranteed outcome: failure. (And their engineers were brilliant but had very little resources to work with.)
Commodore so slowly and ineffectually improving on the OCS didn't help, but the original sin of the Amiga was committed in the beginning, with planar graphics (i.e., slow and hard to work with, even setting aside HAM) and TV-oriented resolutions/refresh rates (i.e., users needing to buy a "flicker fixer"). It's like they looked at one of the most important reasons for the PC and Mac's success—a gorgeous, rock-solid monochrome display—and said "Let's do exactly the opposite!"
Iirc interlaced display and 6 bitplanes were a compromise to allow color graphics in 1985 with the memory bandwidths available at the time.
If it's a sin or feature can of course be debated but I remember playing games on an Amiga in the early 90s and until Doom the graphics capabilities didn't look outdated.
By 1992 with AGA however I agree, flicker and planar graphics(with 8 bitplanes any total memory bandwidth gains were gone) was a downside/sin that should've been fixed to stay relevant.
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At that point in time I would not have called it Wintel yet. That started after Windows 95, IIRC.
Yep. 486DX/2 was when I started seriously looking at moving on from the Amiga. I wound up with a DX/4 100 sometime in 1994.
My classmate kept his Amiga 1200 a bit longer! ...eventually he got a PC with Pentium 60 MHz.
Yeah, there were holdouts of course but the DX/2 really seems like the breaking point.
(Also, a Pentium 60 is barely faster than a DX/2 66 at many tasks — it is a Bad Processor — but that’s another conversation ;)
Pentium is a bad processor? It's way faster than 486, especially on FP it's not even close.
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Many tasks perhaps, but running Quake was not one of them.
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You could play 320x200 Quake acceptably on a P60. On a DX4 too, though barely - my family had both in the mid 90s. I'd be surprised if Quake is playable on a DX2.