Short: Reads the FPU ROM. Send me the output! Author: Anders 'pipe' Andersson Uploader: pipatron gmail com Type: misc/misc Version: 1.0 Requires: FPU Architecture: m68k-amigaos >= 1.2 This tool will read out the undocumented ROM constants from an FPU, and I would like everyone with a physical FPU to run it and report back! Here's why: === BACKGROUND === The MC68881 and MC68882 FPU has a small ROM containing internal constants, such as pi, e, and other more or less useful numbers. These constants can be read out with an instruction called FMOVECR, "Move Constant ROM". Now, there is a paragraph in the M68000PM/AD which made me curious, it goes something like this: "The on-chip ROM contains other constants useful only to the on-chip microcode routines. The values contained at offsets other than those defined above are reserved for the use of Motorola and may be different on various mask sets of the floating-point coprocessor. These undefined values yield the value 0.0 in the M68040FPSP." The reason for the last sentence is that the FMOVECR instruction does not exist on the 68040 and 68060, and is emulated in software. The emulation software does not need these ROM constants, so it only emulates the defined values. There are 128 possible constants that FMOVECR can read, of which only 22 are defined. I have a strong suspicion that the first and second half are mirrored, leaving 42 reserved and unknown constants. I have written a small tool which will extract these constants to a table, format it for easier viewing, and I would like everyone with a *PHYSICAL* FPU to run it and send me the output. === USAGE === Running the tool is very simple. You have to run it from a Shell or CLI, and give the name of the file you want it to create. It will then verify if you have the required hardware, collect the data, and create a text file: fmovecr_dump RAM:fmovecr.txt The file is roughly 9 kB. If the file seems to contain strange hexadecimal digits and stuff, I would like you to send it to me, using one of the following methods: email: pipatron@gmail.com, preferably with "fmovecr" in the title IRC: Highlight pipe on #amycoders @ IRCnet