FPU Compatible Software

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pixelpusher
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Re: FPU Compatible Software

Post by pixelpusher »

thorsten.otto wrote: Sat Jun 05, 2021 3:00 pm
pixelpusher wrote: Sat Jun 05, 2021 1:15 pm - no 68882 support in the LineF emulation, only 68881
Question is: have there ever been SFP-004 boards with an 68882 FPU?
I think SFP boards have always been 68881 only, but the MSTe's implementation is SFP-004 compatible - and you can put a 68882 in its FPU socket instead.
thorsten.otto wrote: Sat Jun 05, 2021 3:00 pm
- cookie support is there, but doesn't consider modifying the system's FPU cookie to make sure LineF based code is used by other apps
That would not make much sense. Applications are either compiled to use LineF instruction, or not (in which case they sometimes fallback to use a memory-mapped FPU). But i don't know of a single application that checks whether LineF is present, and only then uses it. That would be near to impossible.
It would have made a lot of sense, because applications like GB 6 check for the _FPU cookie; as the LineF emulation program doesn't change the cookie's content, GB 6 still only recognizes a SFP-004, which it doesn't support (and it doesn't test speed of the LineF based FPU then either).
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PaulJ
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Re: FPU Compatible Software

Post by PaulJ »

When I put the 68882 in my MSTE a couple years ago I looked for apps that used it but didn't find any I was interested in running. Also when I looked into a C development system I didn't find any that had 68882 support for a 68k. All the support appeared to be for 68020 and up that had the floating point instructions integrated with the processor instruction set. So even though the 68882 shows as being present it's never been used. I guess the 68882 keeps the dust out of the socket. :)
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thorsten.otto
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Re: FPU Compatible Software

Post by thorsten.otto »

pixelpusher wrote: Sat Jun 05, 2021 3:11 pm (and it doesn't test speed of the LineF based FPU then either).
That makes even less sense. You can't compare the speed of LineF instructions that are directly executed by a coprocessor, to something that has to be emulated in software (not completely, but it will still cause an exception, and the protocol has to be emulated).
pixelpusher
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Re: FPU Compatible Software

Post by pixelpusher »

PaulJ wrote: Sat Jun 05, 2021 3:39 pm When I put the 68882 in my MSTE a couple years ago I looked for apps that used it but didn't fine any I was interested in running. Also when I looked in a C development system I didn't find any that had 68882 support for a 68k. All the support appeared to be for 68020 and up that had the floating point instructions integrated with the processor instruction set. So even thought the 68882 shows as being present its never been used. I guess the 68882 keeps the dust out of the socket. :)
PureC allows you to specify that 68881/68882 code should be generated - which is independent from the code for the cpu (which could be 68000 or a newer cpu generation). I'd expect the same from other compilers.

The Motorola eco system was created with the intention to use LineF emulation below the 68020 - and on the Mac you could find LineF emulators that did that.
czietz
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Re: FPU Compatible Software

Post by czietz »

PaulJ wrote: Sat Jun 05, 2021 3:39 pm When I put the 68882 in my MSTE a couple years ago I looked for apps that used it but didn't find any I was interested in running. Also when I looked into a C development system I didn't find any that had 68882 support for a 68k.
Pure C applications, when linked with the default floating point support library PCFLTLIB.LIB, detect the SFP-004 or the memory-mapped FPU in the MegaSTE and use it if available. FPUPATCH claims to increase compatibility with the 68882: http://atariftp.czietz.de/pub/atari/Uti ... upatc1.lzh
pixelpusher
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Re: FPU Compatible Software

Post by pixelpusher »

thorsten.otto wrote: Sat Jun 05, 2021 4:06 pm
pixelpusher wrote: Sat Jun 05, 2021 3:11 pm (and it doesn't test speed of the LineF based FPU then either).
That makes even less sense. You can't compare the speed of LineF instructions that are directly executed by a coprocessor, to something that has to be emulated in software (not completely, but it will still cause an exception, and the protocol has to be emulated).
It for sure has its overhead (on top of the overhead of handling the data r/w on the IO), but compared to creating your own special SFP-004 based floating point libs that you'd have to feed on your own, using the compiler to spit out 68881 code seems to be the easier solution to me - and still should be faster than just the software based floating point lib otherwise used by the compiler.
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PaulJ
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Re: FPU Compatible Software

Post by PaulJ »

I'll have to run the link through the translator... when I see German my eye's glaze over and I usually turn my attention to something else. I have been using Pure C as my perferred development system on the Atari but documentation appears to be its weakest issue. Mark Williams C has good documentation but I was running into strange errors so I went to Pure C which works well for me. There appeared to be a lot more German documentation than English.
pixelpusher
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Re: FPU Compatible Software

Post by pixelpusher »

czietz wrote: Sat Jun 05, 2021 4:32 pm
PaulJ wrote: Sat Jun 05, 2021 3:39 pm When I put the 68882 in my MSTE a couple years ago I looked for apps that used it but didn't find any I was interested in running. Also when I looked into a C development system I didn't find any that had 68882 support for a 68k.
Pure C applications, when linked with the default floating point support library PCFLTLIB.LIB, detect the SFP-004 or the memory-mapped FPU in the MegaSTE and use it if available. FPUPATCH claims to increase compatibility with the 68882: http://atariftp.czietz.de/pub/atari/Uti ... upatc1.lzh
My memory might be cloudy here, but I thought it was the PureC startup code, that triggered these checks (and if you used your own, then potentially there was no check at all for it), wasn't it?
pixelpusher
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Re: FPU Compatible Software

Post by pixelpusher »

PaulJ wrote: Sat Jun 05, 2021 4:48 pm I'll have to run the link through the translator... when I see German my eye's glaze over and I usually turn my attention to something else. I have been using Pure C as my perferred development system on the Atari but documentation appears to be its weakest issue. Mark Williams C has good documentation but I was running into strange errors so I went to Pure C which works well for me. There appeared to be a lot more German documentation than English.
There had been two stumbling stones at that time

- there was some rift between the ATARI market in different countries due to hardware limitations/popularity. E.g. you had to decide what kind of monitor you bought instead of one monitor that can deal with it all (the first multi sync monitor appeared later and was incredible expensive). In Germany the most popular ATARI monitor was the SM124, the UK focussed more on color monitors (and gaming) - with the result that some software hardly considered the pecularities of the ST medium mode (or low mode), while other software hardly used the higher resolution of the SM 124 (or even considered to be written in a way that it also could utilize much higher resolutions).

- there was no european economic area (that was introduced mid 1992) when the ATARI market was striving and every vendor had to deal with all the customs stuff (like in Brexit times). So if you still decided to deal without your country then you had to deal with all this and of course all the expenses needed for translation, printing language specific manuals, etc.
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Darklord
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Re: FPU Compatible Software

Post by Darklord »

pixelpusher wrote: Sat Jun 05, 2021 7:42 am Add PureC to the list...
Thanks!
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