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NutsAboutAmiga
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Re: Amiga's future, or lack of Posted on 31-Jul-2014 15:33:50
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matthey
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Re: Amiga's future, or lack of Posted on 31-Jul-2014 16:26:51
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Joined: 14-Mar-2007 Posts: 1968
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| Quote:
NutsAboutAmiga wrote: Quote:
Moving to 64 bit operations like the other processors that cheat would help the speed some. |
for what I have heard there is little or no speed improvement between 32bit vs 64bit programs, if you have a 64bit version of windows installed you should install a 64bit program, if you install a 32bit program it has to be handled by translation layer, that adds 2% speed penalty. |
Right. A 32 bit CPU design can be faster (faster clock speed and reduced latencies) than a 64 bit design (64 bit is wider so it can sometimes do 2x the amount of work though) but after paying the penalties for a 64 CPU design it is more optimal to use it.
I was referring to the 68k FPU using an 80 bit internal/96 bit load+store extended fp format for calculations instead of the 64 bit IEEE double precision format that the emulators were likely using. UAE has a compatible FPU setting but it may be forced to do all calculations in software (probably integer). The speed of the 68k FPU might not look so bad in comparison. The penalty for the extended fp format is substantial in an fpga also. It could be 20%-40% where it may only be 10% in an ASIC for example. The penalty is somewhat similar to the integer penalty for moving to a 64 bit (integer) CPU. The 68k FPU has 64 bits of fraction/mantissa and must also do 64x64=64 and 64 bit shifts quickly or the whole pipeline is slowed down.
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so it pointless to talk about 64 or 32bit, this mostly about Ghz. and also number of cores does help, programs are primarily serial, AltiVec/VMX/MMX and so on this are more flexible, but require the developer to make an effort to support this, and it might be possible for the CPU emulation to take advantage of this, but I wonder if there is not going to be some overhead, and maybe its not even worth the effort.
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I believe an SIMD unit would be helpful and worthwhile in emulating the 68k FPU, at least sometimes. PPC has pretty good FPU support so it wouldn't need Altivec as much where x86_64 would probably do a lot of work in the SIMD unit as the FPU is handicapped. The x86_64 FPU precision matches the 68k FPU which is convenient if the extra precision of extended precision is required but it would be slow.
Last edited by matthey on 31-Jul-2014 at 04:29 PM. Last edited by matthey on 31-Jul-2014 at 04:28 PM.
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NutsAboutAmiga
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Re: Amiga's future, or lack of Posted on 31-Jul-2014 17:10:53
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Joined: 9-Jun-2004 Posts: 12795
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| @matthey
Quote:
PPC has pretty good FPU support so it wouldn't need Altivec as much where x86_64 would probably do a lot of work in the SIMD unit as the FPU is handicapped. |
I have looked at the FPU instructions a bit for PowerPC, and few things noticed, is the only way to cast some thing from INT to FLOT is by storing it in RAM, and the loading it by the FPU, I find it tricky to balance between FPU and CPU instructions, while VMX/AltiVec there is no issue like that. (So I expect casting might be expensive on a FPU's), The FPU used to be optional co-processor back in 386 days there was empty socket for it.
Your right FPU might be good candidate to run in its own tread if its possible.
I expect most of AmigaOS to be mostly integer code, so I don't think there is lot to gain from it. If it was like 50/50 not 99/1 int/fpu, then yeh. Anyway I have no idea about percentage, anyway Amiga developers have been in love with integer numbers for a long time. (so many CPU models with out any FPU).Last edited by NutsAboutAmiga on 01-Aug-2014 at 01:17 PM. Last edited by NutsAboutAmiga on 31-Jul-2014 at 05:30 PM. Last edited by NutsAboutAmiga on 31-Jul-2014 at 05:13 PM. Last edited by NutsAboutAmiga on 31-Jul-2014 at 05:13 PM.
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matthey
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Re: Amiga's future, or lack of Posted on 31-Jul-2014 20:19:05
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Super Member |
Joined: 14-Mar-2007 Posts: 1968
From: Kansas | | |
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NutsAboutAmiga wrote: I have looked at the FPU instructions a bit for PowerPC, and few things noticed, is the only way to cast some thing from INT to FLOAT is by storing it in RAM, and the loading it by the FPU, I find it tricky to balance between FPU and CPU instructions, while VMX/AltiVec there is no issue like that. (So I expect casting might be expensive on a FPU's), The FPU used to be optional co-processor back in 386 days there was empty socket for it.
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Are you sure Altivec doesn't have to go to memory also for int to float conversions? The pipelines can run faster if they are separate so this makes some sense even though it makes int to float conversions slower. The load/store architecture (CPU, FPU, Altivec in PPC) has bubbles when loading and immediately using a value from memory (multiple conversions at the same time can interleave instructions to hide the bubbles). Unfortunately, single conversions are very common in fp support libraries in my experience (I am working on some vbcc vclib fp math libraries right now). The CISC 68k has no problems going to memory and immediately loading into another pipeline. One of the PPC floating point strengths lies in it's ability to do multiple basic operations in 1 instruction. It's a little off on some of the utility fp functionality I would like to see though. Altivec did a much nicer job of giving the needed fp functionality IMO.
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Anyway your right FPU might be good candidate to run in its own thread if its possible.
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That's not a bad idea as the 68k FPU executes code in parallel in it's own separate pipeline to the integer pipeline(s). This is also what allows the 68k FPUs all the way back to the 68881 to give acceptable results with mixed fp and int code despite slow MFLOPS.
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Anyway expect most of AmigaOS to be mostly integer code, so I don't think there is lot to gain from it. If it was like 50/50 not 99/1 int/fpu, then yeh. Anyway I have no idea about percentage, anyway Amiga developers have been in love with integer numbers for a long time. (so many CPU models with out any FPU). |
There is no direct FPU code in the AmigaOS that I am aware of outside the math libraries. The little bit of fp code uses the math libraries which in turn use the FPU if the hardware is available. The math libraries are considerably slower than direct FPU code but there isn't much floating point code.
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OlafS25
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Re: Amiga's future, or lack of Posted on 31-Jul-2014 22:07:19
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Joined: 12-May-2010 Posts: 6321
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| @NutsAboutAmiga
I read it
If I would only need to buy a license and it would be useable even I would be tempted |
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Metalheart
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 0:46:03
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Joined: 21-Aug-2003 Posts: 2969
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| @NutsAboutAmiga
Where did you read that ?
_________________ Theres a time to live and a time to die When its time to meet the maker Theres a time to live but isnt it strange That as soon as you're born you're dying |
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OlafS25
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 8:11:16
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megol
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 10:10:42
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Joined: 17-Mar-2008 Posts: 355
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| @matthey
X86 and AMD64 have full support for extended precision math so no emulation is required for that. The (modified) stack architecture have some overheads though so double precision code is most likely a bit faster due to SSE/AVX support.
The implementation penalty going from 64 bit double precision to 80 bit extended precision is much higher than that of going from 32 bit integer execution to 64 bit execution. Both the adder and the multiplier circuits expands significantly and the FPU latency have to be increased.
One way to handle this is adding a new mode type where extended precision floats can be done with either the original extended precision or double precision. If one then optimizes the double precision performance as much as possible it is possible to reuse the multiplier circuits by splitting each extended precision operation into several pipelined ones. It would still require extra circuits for the extra precision and would be slower than a native design but perhaps it could be useful?
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elwood
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 11:13:40
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| @NutsAboutAmiga
Quote:
looks like WinUAE is getting PowerPC support |
No, it has support for the PPC cards (Cyberstorm...) but no PPC emulation i.e. the emulated program sees there is an attached PPC hardware but it can't use it.Last edited by elwood on 01-Aug-2014 at 11:14 AM.
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wawa
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 11:14:46
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| @Metalheart
Quote:
Where did you read that ? |
but as toni says he is still not interested in ppc emulation, so dont hold your breath. personally i neither see how would that be of much advantage. |
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NutsAboutAmiga
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 11:36:13
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Joined: 9-Jun-2004 Posts: 12795
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| @elwood
Well they have worked WinUAE detect the ROM's and make Kicktsrat menus work on this cards, as I see they are getting closer to adding PPC support.
I see some advantages of being able to virtualize AmigaOS4.1.
Easier to make recovery CD's / USB sticks. (nice when real hardware is not booting)
Cross Development, there are some really nice text editors and I believe I can use virtual studio write program code. I can test it on my PC instead of coping compiled program to my real AmigaONE. and with out messing with Samba or FTP.
It also makes easier for developers who mostly interested in Classic Amiga to test if there software works on AmigaOS4.1 classic. (well maybe not as restrict as AmigaONE computers), but I hope that some developers see some of there errors, at least AmigaOS4.1 screams DSI error if they do some thing bad (in most cases).
Last edited by NutsAboutAmiga on 01-Aug-2014 at 11:58 AM. Last edited by NutsAboutAmiga on 01-Aug-2014 at 11:38 AM. Last edited by NutsAboutAmiga on 01-Aug-2014 at 11:37 AM.
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terminills
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 11:40:07
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AROS Core Developer |
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wawa
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 12:09:08
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Joined: 21-Jan-2008 Posts: 6259
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| @terminills
damn, id prefer he would invest some work in aros68k instead ;( |
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OlafS25
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 12:33:12
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| @NutsAboutAmiga
it would be useful and Hyperion might even sell some additional licenses |
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phoenixkonsole
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 12:37:01
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Super Member |
Joined: 8-Nov-2009 Posts: 1770
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| @terminills He should Check out Dolphins jit because it works on arm as well and more Important it is under Development . : ) Peapc non jit reached 166mhz 603e Performance on a 1.7ghz A9, while dolphin reaches g3 733+ Speed. _________________ AROS Broadway - AEROS - Aminux - AmiCloud - indieGO! Appstore - AmiWallet - VAN lossless video codec - AMC Amiga media Center -KrypUnite - LibertyNet - MinX - amigaNX |
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terminills
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 12:54:08
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AROS Core Developer |
Joined: 8-Mar-2003 Posts: 1472
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| @phoenixkonsole
He already knows about that. ;) _________________ Support AROS sponsor a developer.
"AROS is prolly illegal ~ Evert Carton" intentionally quoted out of context for dramatic effect |
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terminills
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 12:55:00
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AROS Core Developer |
Joined: 8-Mar-2003 Posts: 1472
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| @wawa
He has been. :)
_________________ Support AROS sponsor a developer.
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KimmoK
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 13:17:40
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wawa
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 13:26:34
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Joined: 21-Jan-2008 Posts: 6259
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| @terminills
its never enough! |
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WolfToTheMoon
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Re: Amiga's future, or lack of Posted on 1-Aug-2014 14:12:33
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Super Member |
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| Will this also run earlier versions of MOS? Maybe MOS Team might make a try-it-out version of the 2.x or 3.x branch for WinUAE... _________________
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