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| Author | Most efficient OS version for a 68040 Mac? (Read 7987 times) | ||||||||||||||||||
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ajmoss
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on: May 09, 2007, 15:58
I'm sure you've been asked many times for an opinion on which version of System 7 is the best for an extremely old Mac, and have replied that any 68030 machine with 8MB of RAM and a 32-bit clean ROM will run 7.6.1 nicely. My question is slightly different. In another vintage Mac forum, I have asked about the possibility of decoding MP3 files in real time with a 68040 Mac, for the purpose of using said Mac as a MP3 jukebox. Even though in general you'd need a good PCI PowerMac to play 320kbps, 16-bit stereo MP3s, something with an unchallenging bit rate may be playable on a 40MHz 68040 Mac, using a MP3 decoder specifically optimised for that CPU; and a few suitable decoders exist, having been ported from the 68040 Amiga. For this purpose, every CPU cycle counts. Am I right in thinking that System 7.5.5 is leaner than OS 7.6.1, and System 7.5 (with Finder 7.1.4 and a suitable Enabler) is even less demanding of CPU time? Can you think of anything in OS 7.6.1 that I would definitely need for this project, or do I have a more or less free choice between these System versions? The MP3 decoder requires Quicktime 2.1 or better. Would there be any speed advantage in using QT 2.1 or 2.5, rather than the more readily available QT 4.0.3? |
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wove
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1024 MB  Posts: 1363 
Reply #1 on: May 09, 2007, 16:49
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The only native 40MHz 68040 Mac is the Quadra 840. If an mp3 decoder had been written using the onboard DSP chip for decoding the Q840 would have made an outstanding mp3 player. Since nothing was written all the work is handled by the 68040 processor and that presents a challenge. When challenging the resources of a system the most important consideration is ensuring that the application gets all the resources it requires. This is first done by adding resources to the hardware such as RAM and fast hard drives. Secondly one wants to make sure that those resources are committed strictly to the application. While OS 7.6.1 is more stable than System 7.1, the point is somewhat moot in that all one requires is sufficient stability to successfully run the application is question. Every incremental increase in the OS adds features and capabilities to the OS that in turn use more of the hardware resources. In some cases that improves access to hardware resources and improves the speed at which the application can run. In other cases those additions add overhead that will provide no benefit to a particular application. The "perfect" balance is a matter of experimentation. This can be approached by either starting with a newer system and stripping it down until it has just what is needed or starting with and older system and adding items that are needed. And example of both approaches can be found here. There is a little used trick in the Mac OS that can greatly aid in concentrating resources in a specific application. The Mac Finder is just an application. A special one and one that resides in the system, but none the less it is simply an application that starts first after the system loads. Using Resedit or several other utilities one can change the type and creator codes for an application to those of the Finder. The application is then renamed "Finder" and replaces the regular Finder in the System Folder. At this point the Mac can be restarted and rather than coming up to the Finder the system will start with the application running. The Finder will not be present, so none of its functions will be available, however it will not be using any resources either. That means that RAM etc that the Finder uses will be free for use by your application and any background tasks that the Finder runs will also not be running either. bill
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dpaanlka
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1024 MB Posts: 1646
Reply #2 on: May 09, 2007, 18:54
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Just a few thoughts on this issue: In the past I've tried every which way to get 68ks to play MP3s suitably. The result? It's a complete waste of time. Even on Quadras. With even the earliest PowerPC systems having much better results, and also costing almost nothing, there is really not much reason to do this, other than for the sake of being able to say you did it. It will work, but it'll never be high enough quality to actually want to listen to. Also, the third number in the "7.5.5" or "7.6.1" are usually just bugfix patches and such. You should never run a version of System 7.5.x previous to 7.5.5, for example.
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ajmoss
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Reply #3 on: May 09, 2007, 20:45
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The first reply I got to my question about MP3s on a 68040 Mac is as follows. Did you try using either of the two MP3 decoders referenced? From the Readme file of Mpg123 v1.1: Mpg123 68k 1.1. This is a mac port of mpg123-0.59r to macos for macs with a 68040 (fpu not needed). Mpg123 requires Quicktime 2.1 or above. [...] Here is a rough speed guide. 68040 40Mhz should play 22050Hz mp3 files in stereo, 44100Hz mp3 files in mono using the -2 -m switches. 68040 33Mhz plays 16000Hz mp3 files in stereo, 44100Hz mp3 files in mono using the -2 -m switches. Main testing was done on a LC 575 68040 33Mhz mac. Sound Hardware on a LC 575 is 22050 8 bit stereo. From the Readme of MpegDec2: MPEGDEC 2.0 is a Macintosh Port of Stephane TAVENARD's excellent MPEGDEC mp3 decoder. It was originally designed for 68k amigas and as the 68k amigas and 68k macs share the same cpu, a very fast port was possible. It uses 68k assembly language optimizations and is the fastest mp3 decoder for 68k cpus. [...] For 68040 macs downsample by 2 should always be selected when playing 44100Hz mp3's. Here is a rough preferences guide for playing 44100Hz 128kbps mp3 files. For 40Mhz 68040 macs quality = 1 or 2 should work in stereo mode. For 33Mhz 68040 macs quality = 0 should work in stereo mode. For other 68040 macs quality = 0 or 1 should work in mono singlemix mode. Downsampling by 4 in mono singlemix mode will probably play 44100Hz 128kbps mp3 files on a 68030 50Mhz. The mp3 types MPEGDEC 2.0 can use are 'MPG3' 'MPEG' 'PLAY' 'MP3 '. If the mp3 file type is anything else you will need to change it to one of the above.
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tomlee59
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8 MB Posts: 12
Reply #4 on: May 11, 2007, 04:45
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There's really only one choice, and that's MpegDec. Mark White has done a nice job with the latest versions (3.11 is the most recent, IIRC), and you will get playable results with an '040 on MP3s at 128kb/s. Critical portions have been hand-crafted for speed. No eye-candy; just what is needed to get the job done. Mpg123 was also ported by Mark White before he set to work on MpegDec. I found Mpg123 to have mysterious problems on some Mac/OS combinations, so I haven't tried it in ages. Once I found MpegDec, there was no need to, anyway.
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