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Improved floating point emulation for RISC OS

By Chris Williams. Published: 1st Oct 2002, 18:47:57 | Permalink | Printable

Mech's SuperFPEm 2.33 released [Updated]

Floating point handling is a much discussed area of RISC OS hardware, as it's always been something that the platform has been lacking. As processors like ARM chips deal with integers, floating point calculations are usually handed over to a special secondary processor, a Floating Point Unit, which is optimised for such processing. However, modern RISC OS hardware that uses StrongARMs, ARM710s and ARM610s don't pack a FPU so these floating point calculations need to be done in software on the ARM processor via the Floating Point Emulator module.

Step in SuperFPEm, developed by Dan "Mech" Maloney, who has today announced the release of SuperFPEm version 2. According to Dan, SuperFPEm speeds up floating point maths for RISC OS machines using StrongARM, ARM710 and ARM610 processors.
"Once upon a time a chappy called Niall Douglas (known for wimp2) hacked the FPEmulator to speed up a dodgy release of Acorn Quake", Dan explains in his announcement. "He uploaded it to Hensa and I downloaded it and intrigued, continued the reverse-engineering 'just-for-fun'. Eventually, after trying rewriting lots of it, it got called 'SuperFPEm' and I put it on my webspace for a while."

At the time, Dan tried to update SuperFPEm to fix a few issues but failed in his attempts.
"..over a year since my last attempt, I've got a new RISC-like strategy", continues Dan. "I've decided to cut out vast quantities of the source code and concentrate on the bits that matter. In doing so, I've discovered lots of bugs in SuperFPEm that I never had a clue existed. It's much more reliable now."

Public health warning
drobe.co.uk would like to point out that SuperFPEm is a very low level piece of software and any faults or bugs may well result in your system crashing to a halt. However, if you know what you're doing and want to help Mech fix any remaining problems, you're invited to email him.
"I've tested it a lot and am quite happy with it", Dan boasts, "but I still would like anyone who tries it and has any problems to drop me an email, because the whole aim was to clear up all the problems with it, so I can say I finished the job."

Updated
Mech as updated his SuperFPEm software to 2.33 straight after releasing 2.32. As well as engineering a small performance improvement, Mech also explains,
"Embarassingly, SuperFPEm 2.32 didn't work with RISC OS Select's version of FPEmulator (4.10). This was entirely my own fault, due to poor research. (SuperFPEm 2 has to know how to access the FPEmulator's workspace and I seem to have assumed it worked like 4.14 when in fact it works like 4.09)."


Links

SuperFPEm 2.33 download

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Discussion

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Any estimates as to possible performance increases? -- Rich Cheng

 is a RISC OS Usersedm0784 on 2/10/02 2:40PM
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I tried running benchmark tests on my StrongARM RISC OS 4.29 RiscPC tonight, but SuperFPEm failed to complete the tests. The benchmarks used were the portable and famous Linpack test (built for RISC OS using GCC) and the Whetstone section of the RISC OS native benchmark app SICK. SICK reported a floating point exception. I'll contact Mech about this as soon as I can.

If I get time again, I'll run simpler tests, such as calculating e using FP.

Chris hard-resets-suck department, drobe.co.uk

 is a RISC OS Userdiomus on 2/10/02 11:11PM
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I feel sorry for your machine diomus. :)

 is a RISC OS UserSnig on 3/10/02 10:43AM
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If you ever start doing low level programming, hard resets become a good way to force a coffee break. At least RISC OS bounces back quickly from a reset.

Chris, I-like-lots-of-coffee fan club, drobe.co.uk

 is a RISC OS Userdiomus on 3/10/02 11:39AM
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Yours might mate, mine doesn't. I took my ADFS HD out the other day - BIG mistake that was. Hard resets are now a multiple-tea-break event until I put another one back in :o(. YES, I have configured it correctly - I think it's cos it decides to talk to my CD ROM on startup, which is always a Bad Thing (TM) to do. -- Andrew Hill, More-a-tea-man-meself

 is a RISC OS Usermd0u80c9 on 3/10/02 2:27PM
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unplug cdfssoftatapi then

 is a RISC OS Usermavhc on 3/10/02 11:20PM
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Article updated. The reason, as Mech points out, I couldn't test his software was that it didn't work with the Select FPEm.

Chris, drobe.co.uk

 is a RISC OS Userdiomus on 5/10/02 10:05PM
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Blimey, I get a 75% increase in FP perfomance if SICK is to be relied upon. Ney bad! -- James Carey

 is a RISC OS Userjmcarey on 11/10/02 12:48PM
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