phil@uxg.cso.uiuc.edu (12/21/88)
For TRIVIAL extended precision work, IBM VM/CMS Rexx language has N-digit precision fixed and floating point numbers, but NO function library. It is SLOOOOOW, but it is handy for those few small calculations needing an infinite precision. I have implemented a SQRT function with variable precision under Rexx. I wish some machine had truly VARIABLE precision firmware floating AND FIXED point (i.e with fractions) arithmetic. On a RISC machine, an architecture that allowed easy extension of precision would be just as good. --phil--
news@ism780c.isc.com (News system) (12/22/88)
In article <400001@uxg.cso.uiuc.edu> phil@uxg.cso.uiuc.edu writes: >I wish some machine had truly VARIABLE precision firmware floating AND FIXED >point (i.e with fractions) arithmetic. One machine did provide just this. It was the IBM/1620. The precision of both fixed point (not necessarily integer) and floating point arithmetic was varaible from 2 decimal digits up to a maximum limited only by the amount of main memory available. (Yes I said DECMAL digits). The FORTRAN compiler provided for integer precision of 4 to 10 digits and floating point precision of 6 to 20 digits. The main reason for the relatively small upper bound on floating precision was the difficulty of providing a math library of unlimited precision. The machine was a little slow by todays standards. An integer add of 5 digits took 580 microseconds (480 on the model 2). Marv Rubinstein
landman%hanami@Sun.COM (Howard A. Landman) (12/22/88)
In article <400001@uxg.cso.uiuc.edu> phil@uxg.cso.uiuc.edu writes: >I wish some machine had truly VARIABLE precision firmware floating AND FIXED >point (i.e with fractions) arithmetic. On a RISC machine, an architecture >that allowed easy extension of precision would be just as good. I believe that at least some of the Connection Machine languages allow fairly arbitrary precision. Certainly, the hardware is capable of it within the limits of processor memory (up to ~64K bits). Howard A. Landman landman@hanami.sun.com
mcdonald@uxe.cso.uiuc.edu (01/01/89)
(Story about 128bit instructions, emulation, phone calls, and smileys). How about it? I would have taken a count of emulated instructions and stored it in a disk file. Does the notorious MicroVax do this? Does MIPS? Does anybody? It seems like a great idea.
aglew@mcdurb.Urbana.Gould.COM (01/05/89)
>We did a weird thing :-) at MIPS with these instructions. Whenever one >of these instructions is encountered, the trap handler emulates the >instruction, AND it does something else. :-) It instructs the console >maintenance processor to activate its remote-diagnostics modem, which >dials a special phone number back at the factory, here at MIPS. In fact >it dials a phone which sits on my desk :-). The maintenance processor >logs the date and time, the serial number of the machine, and the type of >longer-precision operation that was requested :-). > >So far, in over 2 years, the phone has never rung. :-) Thus it is >tempting to conclude that user programs do not suffer a serious >performance degradation from emulating longer-precision (80 and 128 bit) >floating point operations in software :-). > > -- Mark Johnson What a beautiful story! I love it! But, one question: are remote diagnostic modems optional on MIPS systems? They're optional on most of the computer systems I've used (anonymous 68K boxes, Goulds, Motorola VME systems) and I've never yet worked on a system that exercised that option.