picard@milton.u.washington.edu (Mary Stumpel) (03/24/91)
With all this talk about MIPS etc, it has me wondering: 1.What exactly does MIPS measure? 2.What are MFLOPS? 3.What is the connection between MIPS and Mhz? e-mail answers, oh hardware gurus. Thanks.
jo0e+@andrew.cmu.edu (Jared M. Oberhaus) (03/29/91)
MIPS stands for Millions of Instructions Per Second. MFLOPS (or MegaFLOPS) stands for Millions of FLOating Point operations per Second. Or if you use a Cray Y-MP, you'd use GigaFLOPS! Mhz obviously stands for MegaHertz, or Millions of [clock] cycles per second. The measuring of Mhz in a system is only a truly valid measure of speed if you're comparing two machines at different clock speeds with the same processor. Other comparisons sometimes are relevant, but many times are way off. MIPS is a true measure (as far as the CPU goes) of how fast a machine really is. For instance, the new 68040 Macs due soon will use a 68040 processor at 25Mhz. These machines will be 4 to 12 times faster than a 40Mhz 68030 IIfx. The 25Mhz 68040 will run at about 15 MIPS compared to about 3 or 4 MIPS on a IIfx. The reason for this is that the 68040 is truly a RISC in CISC clothing, and uses less clock cycles, or Hertz, to accomplish the same number of instructions (technically speaking, the instruction decoder on the chip only searches a limited list of CPU instructions in most cases.) This results in more MIPS. Imagine what a 68040 at 40Mhz will be like! In this case, the 40Mhz 68040 will be almost twice as fast as a 25Mhz 68040, ceteris paribus. As far as MFLOPS or GFLOPS are concerned, this is a function of many different factors. For instance, if there is no math coproccessor, like a 68882, it will depend on the software algorithms. Given a coproccessor, it depends on the clock speed and efficiency of the that. In either case, it is dependent upon the level of precision used in the calculations, such as 80-bit, 32-bit, or whatever. Besides, this measurement is usually only applied to Crays or large mainframes where all those numbers flying around are real important. (Where do I get an ADB mouse and Microsoft Word for my Cray, anyhow?) Hope that answers your questions! See ya!
majeske@remus.rutgers.edu (Joseph Majeske) (04/02/91)
Lets get something straight here. RISC - Reduced Instruction Set Computer. The 68040 is a CISC - Complete (or Complex) Instruction Set device. It has the esentially same instruction set as the '030. Its blazing speed is derived from extensive pipelining and clever handling of branches, not reducing the rich 680X0 instruction set. One major implication of the '040 is that CISC is far from dead. So, hey, its just not a RISC. :)