joem@nos850.UUCP (Joe Muller) (10/12/90)
I have an opporitunity to purchase a used A2500/020 and was just wondering what am I missing out on by getting an 020 instead of an 030 (other than speed) ?
joseph@valnet.UUCP (Joseph P. Hillenburg) (10/14/90)
joem@nos850.UUCP (Joe Muller) writes: > > I have an opporitunity to purchase a used A2500/020 and was just > wondering what am I missing out on by getting an 020 instead of an > 030 (other than speed) ? Yes. The 030 has some other code, and the 030 boards, at least today, are usually cheaper, plus the 030 boards can run at higher speeds. BTW..does anyoe know the max speed of the 040? -Joseph Hillenburg UUCP: ...iuvax!valnet!joseph ARPA: valnet!joseph@iuvax.cs.indiana.edu INET: joseph@valnet.UUCP
podop03@bingsuns.cc.binghamton.edu (Kriston J. Rehberg) (10/15/90)
Well, I believe an '020 has most of the same instructions (if not all of them) of the 68030, but it seems to require an external MMU (the 6551). The 68030 has this MMU built-in. Be sure when you buy the card that it comes with a math coprocessor, because having an accelerator card without one is not too good of a thing to do (math coprocessors take over integer functions so the 680x0 can do other things!). By the way, a 68040 is a processor that contains the CPU, MMU and the math coprocessor! By putting all of this stuff together you get the opportunity for a good speed increase. .=============================================================================. | Kriston J. Rehberg | "Only Amiga makes it possible" | | podop03@bingsuns.cc.binghamton.edu .======================================.=' | podop03@bingvaxa.bitnet / The POD will be a better place \ `==================================| Once the XBALANCE system has been erased | `=========================================='
rehrauer@apollo.HP.COM (Steve Rehrauer) (10/15/90)
In article <4186@bingvaxu.cc.binghamton.edu> podop03@bingsuns.cc.binghamton.edu (Kriston J. Rehberg) writes: > Be sure when you buy the card that it >comes with a math coprocessor, because having an accelerator card >without one is not too good of a thing to do (math coprocessors take >over integer functions so the 680x0 can do other things!). Goodness, no! The Motorola math coprocessors do floating-point, and int<->float conversions, only. Chip->chip communications between a 680x0 and a 6888x coprocessor are slllooowwwww by comparison with integer instructions that the 680x0 executes itself. > By the way, >a 68040 is a processor that contains the CPU, MMU and the math >coprocessor! By putting all of this stuff together you get the >opportunity for a good speed increase. Given equal clock rates, anticipate 1-3x integer performance and 2-10x floating-point performance going from a 68030+6888x to a 68040. The integer speedup is mostly due to bigger instruction & data caches. (The 68040 doesn't implement the full instruction set of a 6888x FPU, so your float mileage will vary depending upon the instruction mix in your code. If you take code that was compiled for a 6888x coprocessor and run it on an '040 box, you're probably going to be trap-emulating some 6888x instructions, which is a big performance loser. I think some people are going to be surprised when they take big number-crunchers compiled for a 68030+6888x and move it onto a 68040 -- it mayn't run all that hot, as it would if the compiler were tuned for the 68040 float instruction mix.) -- "I feel lightheaded, Sam. I think my | (Steve) rehrauer@apollo.hp.com brain is out of air. But it's kind of | The Apollo Systems Division of a neat feeling..." -- Freelance Police | Hewlett-Packard
daveh@cbmvax.commodore.com (Dave Haynie) (10/17/90)
In article <4d6635ba.20b6d@apollo.HP.COM> rehrauer@apollo.HP.COM (Steve Rehrauer) writes: > Given equal clock rates, anticipate 1-3x integer performance and >2-10x floating-point performance going from a 68030+6888x to a 68040. >The integer speedup is mostly due to bigger instruction & data caches. Well, that's hardly where the difference ends. The '040 has a good portion of its instructions hard wired, so they execute faster. It has a deep and clever pipeline, so you tend to get cool and unexpected speedups. For instance, offsets and increment/decrements are basically free on the '040, since a separate ALU handles this is a stage before the main ALU action. Also, the '040 ALU and other internal events are clocked at twice the rate of the bus clock. And the cache is not only larger, it's four set associative. Cache hits are as fast as registers. And there are separate data and instruction MMUs, each with 64 entry ATCs, versus the single 33 entry ATC in the 68030. And the list goes on. I think Moto really did their homework on this baby. Now if only they can get into full production. > (The 68040 doesn't implement the full instruction set of a 6888x >FPU, so your float mileage will vary depending upon the instruction >mix in your code. If you take code that was compiled for a 6888x >coprocessor and run it on an '040 box, you're probably going to be >trap-emulating some 6888x instructions, which is a big performance >loser. I think some people are going to be surprised when they take >big number-crunchers compiled for a 68030+6888x and move it onto a >68040 -- it mayn't run all that hot, as it would if the compiler were >tuned for the 68040 float instruction mix.) Of course, Motorola claims their emulation library is as fast or faster than the 68882 at the same speed. That really remains to be seen. If the internal FPU instructions are really as fast as the manual claim, you'll probably want to recompile all your math intensive code for 68040 and in-line the smaller functions that are missing from the hardware, at least for maximum performance. The same really goes for integer code as well -- there are many places where several simpler instructions will kick the butt of a single complex one (this is even the case, to a small extent, on the '030...). >"I feel lightheaded, Sam. I think my | (Steve) rehrauer@apollo.hp.com -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy Standing on the shoulders of giants leaves me cold -REM