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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. Befo
by einr 5mo 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.
- darkwater 5mo agoAt that point in time I would not have called it Wintel yet. That started after Windows 95, IIRC.
- whizzter 5mo agoAs 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 https://news.ycombinator.com/item?id=47717334
- einr 5mo agoThe 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…
- actionfromafar 5mo agoThere 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.)
- whizzter 5mo agoWas 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.
- fredoralive 5mo agoThe argument is that 68k is "CISCier" than x86, the addressing modes in particular, so making a performant modern out-of-order superscaler core that uses it would be harder than x86.
- actionfromafar 5mo agoI believe in that. But Commodore could have plunked a cheap 68020 in their machines for backwards compatilibity (like how MSX2 had a SOC MSX1 inside, PS2 had a PS1 SOC, PS3 had a PS2 SOC, and so on) and put another "real" socketed CPU as a co-processor. Or made big-box machines with CPUs on PCI cards, for infinite expansion options. "True" multitasking, perfect for CAD, 3D rendering and non-linear video editing. It would have been very cool with an architecture where the UI could be rendered with almost hard realtime and heavy processing happened elsewhere.
- 5mo ago
- feintruled 5mo ago> 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).
- whizzter 5mo agoAh, 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#msg544232 https://forum.amiga.org/index.php?topic=51616.msg544232#msg5...
- actionfromafar 5mo agoWhich brings me to my pet peeve, the already slow 68020 (680ec20) at 14MHz was crippled by, even though it had a 32-bit bus, was only connected to a 16-bit RAM bus. (Chipram.) This 16-bit memory (2 megs) is also where the framebuffer and audio lives, so the stock CPU in A1200 has to share bandwidth with display signal generation and the graphics and audio processing. All-in-all, it meant the Amiga 1200 had only about twice the memory throughput of the Amiga 500. (About 5 megabytes/s vs about 10 megabytes/s) If the A1200 had at least some extra 32-bit memory (it existed as a third party add-on) the CPU could have had its own uncontested memory with a troughput of about 20-40 megabyte/s. Imagine the difference it would have made if the machine had just a little extra memory. That's just a tiny detail. That the chipset wasn't 32-bit was another disappointment. The bigger problem was that Commodore as a company was aimless.
- icedchai 5mo agoYeah, and it took ~7 years to make those marginal improvements over the earlier Amiga chipset! I'm ignoring ECS, since it barely added anything over OCS for the average user.
- TMWNN 5mo agoCommodore 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!"
- whizzter 5mo agoIirc 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.
- smallstepforman 5mo ago5 sins in 1992: - 8 bit planar instead of chunky - progressive display (vs interlaced) - sound was not 16-bit - should have been 68030 with mmu support (vs 68020ec) - HD mandatory. If they addressed this, the Doom experience would have run better on Amiga.
- gattr 5mo agoMy classmate kept his Amiga 1200 a bit longer! ...eventually he got a PC with Pentium 60 MHz.
- einr 5mo agoYeah, 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 ;)
- Synaesthesia 5mo agoPentium is a bad processor? It's way faster than 486, especially on FP it's not even close.
- Sheeplator 5mo agoThe Pentium was great, but the 60 and 66MHz versions were not liked, they ran way too hot.
- phicoh 5mo agoI think from the price people also expect a similar performance boost as going from 386 to 486. What made Pentium also confusing is that during this time Intel introduced PCI. From a 486 with VLB to a Pentium with PCI everything became a lot nicer.
- qubex 5mo agoThey ran on 5V supplies and it was only later that the whole architecture was changed to 3.3 V with the 90 and 100 MHz Pentiums (which were then discovered to have the infamous FOOF division bug).
- einr 5mo agoThe original Pentiums (socket 4, 60 or 66 MHz) had the infamous floating point division bug, had underwhelming perf for anything not FP bound (most things), ran hot, and were too expensive for what you got. A DX/4 100 was nearly always a more rational choice. Second gen Pentiums, starting with the 75 MHz, were great.
- icedchai 5mo agoYep. 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.
- bombcar 5mo agoI 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.
- Sheeplator 5mo agoNearly correct. The DX/4 100MHz had a 33MHz bus. The DX/4 75MHz had the 25MHz bus. I remember well because I had both.
- bombcar 5mo agoNow I remember being annoyed that it wasn't the DX/3 as it should have been!
- einr 5mo agoEspecially since when actual clock quadrupled chips eventually came out they had to call themselves ridiculous things like ”5x86” instead of DX/4. (The Am5x86 133 runs at 4x33 MHz)
- cout 5mo agoI think 5x86 had more to do with marketing than anything else, because the Pentium had already been on the market for a while when the Am5x86 came out.
- einr 5mo agoI think it’s a bit of both. It absolutely tried very hard to pretend that it was a ”586” (Pentium class) but also ”5x” is right there and implies that if the DX4 is 4, this is 5. The full name on the chip on some of them is ”Am5x86-P75 DX5-133” which implies a lot of things, some of which are flat out misleading (it does not get very close to ”P75” performance)