sarrel@sioux.cis.ohio-state.edu (Marc Sarrel) (07/11/89)
A friend of mine just bought at 16MHz 68000 accelerator card for his SE. How much performance difference is there between a 16MHz 68000 and a 16MHz 68020? A while back I was considering buying a 68020 accelerator for my Plus, but I decided that I didn't really have the money. Also, there are problems. You have to buy more memory to put on the separate board to take advantage of the wider data path and at least one manufacturer required you to rely on them for _modified_ system software (not just an init) in order to use there product. Unfortunately, that manufacturer had the best, most comprehensive package (also the most expensive). There were also compatability problems. Even some software that would run on a Mac II, would not run on a Plus with some 68020 accelerators. Are 68000 accelerators a cost effective alternative? Can you get faster then 16MHz? I don't want to be dependant on a small company for modified system software and I don't want to have strange compatability problems. Also, even if a '020 board works with the current system, will it work with future systems releases? I figure that the 68000 boards are the saftest although probably not the best performance wise. Any comments, suggestions and helpful hints will be appreciated. --marc -=- "Master, why is the letter 'i' the symbol for current?" "Because there is no letter 'i' in the word 'current'." "Master, why do we use the letter 'j' for sqrt(-1)?" "Because we use the letter 'i' for current." Whereupon the Master struck the Disciple, and the Disciple became enlightened.
siegel@endor.harvard.edu (Rich Siegel) (07/11/89)
In article <SARREL.89Jul10202542@sioux.cis.ohio-state.edu> sarrel@sioux.cis.ohio-state.edu (Marc Sarrel) writes: >SE. How much performance difference is there between a 16MHz 68000 >and a 16MHz 68020? Roughly a factor of two, on the side of the 68020. >problems. You have to buy more memory to put on the separate board to >take advantage of the wider data path and at least one manufacturer The Radius Accelerator 16 for the Mac Plus doesn't require additional memory; it has a 32K SRAM cache for performance, with no sockets for additional memory. This was a win for Radius (IMHO) for two reasons: - When SIMMS were in short supply, they were one of the few accelerator makers who were able to keep up their volume of boards. - Not relying on SIMMs for additional memory keeps the cost down. >expensive). There were also compatability problems. Even some >software that would run on a Mac II, would not run on a Plus with some >68020 accelerators. The Radius Accelerators are fairly compatible; the new ROMs for the Plus model are a big improvement. >Are 68000 accelerators a cost effective alternative? Can you get It depends on the performance. 68000 boards to tend to be half the price, but they're also have the speed. Besides that, a 68020 board with a 68881 or 68882 sitting on its coprocessor bus will do floating point much faster than a 68000 with the FPU mapped in as a peripheral. I have no association with Radius except as a satisfied customer and occasional beta site. -Rich ~~~~~~~~~~~~~~~ Rich Siegel Staff Software Developer Symantec Corporation, Language Products Group Internet: siegel@endor.harvard.edu UUCP: ..harvard!endor!siegel I classify myself as a real developer because my desk is hip-deep in assembly-language listings and I spend more than 50% of my time in TMON. ~~~~~~~~~~~~~~~
daveh@cbmvax.UUCP (Dave Haynie) (07/11/89)
in article <SARREL.89Jul10202542@sioux.cis.ohio-state.edu>, sarrel@sioux.cis.ohio-state.edu (Marc Sarrel) says: > A friend of mine just bought at 16MHz 68000 accelerator card for his > SE. How much performance difference is there between a 16MHz 68000 > and a 16MHz 68020? It depends on the system. If you're accelerating a 16 bit machine and not adding any faster memory, a 68020 will in some cases go about maybe 15%-30% faster than the 68000, depending on how well the instruction cache gets utilized. It's actually possible for a 68020 to go slower than a 68000 when on a 16 bit bus, since the 68020 always prefetches 32 bits for instruction processing, though sometimes only 16 bits worth actually gets used. Once you add some 32 bit memory to a 68020, you get real performance increases. The 16MHz 68020 plus some reasonably fast 32 bit memory will get you about 200%-400% speedup over your 7.8Mhz 68000, and a little better than twice the performance of a 16MHz 68000 with fast 16 bit memory. That's all integer performance. If you add a 68881 or 68882 to the 68020, and your software knows about math chips, you may get a floating point performance increase from 25x-100x what a plain 68000 is capable of. I don't know how well the Mac software would integrate any of this, but the hardware driven increases tend to be similar among all 680x0 machines. > Are 68000 accelerators a cost effective alternative? It depends. Without faster 16 bit memory, it's going to boost your performance by maybe 15% or so overall. With the faster memory, it'll come close to doubling the performance, providing the Mac can be set up to use that fast memory before its on-board slower memory. > Can you get faster then 16MHz? Not likely. The 16MHz (actually, 16.6667MHz; Motorola CPUs are rated by the time of the clock cycle, in this case 60ns) part is currently the fastest 68000 anyone makes. > --marc -- Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: D-DAVE H BIX: hazy Be careful what you wish for -- you just might get it