On Mon, 17 Oct 2016 15:29:10 -0600, Kevin Handy <khandy2...@gmail.com> wrote:
How close are the simh emulators to the real hardware's floating point? How > exct is the emulation of FPU's? > Does simh emulate the real hardware close enough that you can use it to > analyze the original hardware floating point processors? (For those that > actually had FPUs instead of doing it in software). > Or does it do it using "modern" methods (IEEE style FPUs) that could > calculate different results than the original hardware did? > I can tell that the engineering ALU test passes in the BESM-6 emulator. Addition and multiplication produce 80 bit of mantissa and had to be emulated with integers; division produces 40 bit, but using IEEE double and truncating or rounding the result causes the test to fail; I had to implement the non-restoring division algorithm exactly as described in the docs to make it work. It;s probably not a big deal for most users, but if the simh FPU hardware > might operate any different;y than the real hardware it should at least be > documented somewhere. > If other machines emulated by SIMH use IEEE for speed, it would be interesting to run their engineering tests, if available, to see if there are any failures. Leo
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