zaphod@madnix.UUCP (Ron Bean) (01/17/90)
Why hasn't anyone marketed a small circuit board containing a 68010 and an MMU that would plug into any socket intended for a 68000? Any of the 68000-based micros would benefit greatly, although you might need a new operating system. The only reason I can think of is that most users of those machines either don't know what an MMU could do for them, or if they do, they spend the bucks for a 68020 (and an MMU).
dpm@k.gp.cs.cmu.edu (David Maynard) (01/18/90)
> Why hasn't anyone marketed a small circuit board containing a 68010 > and an MMU that would plug into any socket intended for a 68000? > ... > The only reason I can think of is that > most users of those machines either don't know what an MMU could do > for them, or if they do, they spend the bucks for a 68020 (and an MMU). This is probably good reason. For one, you gain the co-processor interface on the '020 and can attach things like the '881 math chip. A couple of years ago we built a daugterboard consisting of an '020, an '881, and 2 PALs that plugged into the '010 socket on a Sun-2. Motorola actually had an ApNote that told you how to build such a board. We had to modify the PAL codings to make it work on the Sun (they played fast and loose with DTACK), but got it working without too much problem. One company (Computer System Associates, San Diego) sells several daughterboard configurations that allow you to upgrade your 680x0 processor. Their board didn't work with the Sun-2 (not their fault) so we ended up rolling our own. If anyone sells a 68000 upgrade they would be a good bet. Software compatibility was still a problem. We wrote a version of Alpha (our distributed, real-time OS) that ran on the '020/'881 and used it to provide hardware floating point to a sample application (an air-defense system written by General Dynamics). Soon afterward, however, the majority of the Alpha development effort was transferred to Concurrent Computer Corp. Since they have more modern hardware (MIPS-based) we stopped playing with the '020 upgrade for the Sun-2. I toyed with the idea of modifying SunOS to work with the '020 upgrade, but never got around to it. Since the Sun already has an MMU and the clock speed is fixed, you mainly gain the floating-point support. I rarely do FP calculations so the motivation wasn't that great. -David --- David P. Maynard (dpm@cs.cmu.edu) Dept. of Electrical and Computer Engineering Carnegie Mellon University, Pittsburgh, PA 15213 --- Any opinions expressed are mine only. I haven't asked the ECE department or CMU what they think. ---