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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: desantii on December 14, 2009, 06:09:26 PM
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Is there a real benefit of overclocking the 68882? I have a 50mhz 030 board and the 68882 actually overclocks and works fine up to 66mhz. What programs use the co proc? is it really worth overclocking?
thanks
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Is there a real benefit of overclocking the 68882?
No, not really.
I have a 50mhz 030 board and the 68882 actually overclocks and works fine up to 66mhz. What programs use the co proc?
Excuse my silly question, but... How can you tell that it's working fine if you haven't tested it?
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Through AIBB and Sysinfo
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Through AIBB and Sysinfo
They don't tell you if the FPU is actually producing correct results. Also, they don't stress the FPU long enough to give any indication about the reliability.
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Is there a real benefit of overclocking the 68882? I have a 50mhz 030 board and the 68882 actually overclocks and works fine up to 66mhz. What programs use the co proc? is it really worth overclocking?
thanks
The overclock will be beneficial to programs that are designed to use the 68882. Like 3d rendering software/graphics/fractals and some audio software too. But you have to make sure that when you install such software that you select the option (if available) that your computer has a maths co processor (FPU). You must do this or it will install the Integer (non FPU) version, and your 68882 will be sat there generating alot of heat and for nothing!
Programs that I use that make use of the FPU are Vistalite, VistaPro, Distant Suns and Audio Evolution. Also, I have a Squirrel SCSI interface which I have a cdrom drive connected....the squirrelscsi.device driver I am using is the FPU version (comes in FPU, 68000 and 68020 versions). So even device drivers and the like can make use of the FPU if there is such a version available.
But for general use, overclocking the FPU will achieve nothing UNLESS you are using an FPU specific version of your program.
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Any recomendation on what to tress test with?
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Ok, just saw the above post, will try with some of that SW
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Any recomendation on what to tress test with?
If you use AIBB and render the beachball, and there is no graphics corruption in the render...then according to AIBB documentation, your FPU is working correctly.
I bet the 68882 is running hot though, and I highly recommend either using a heatsink or a fan to keep it cool.
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I did run the beachball and it was fine, did it 5 times in a row. Actually the 68882 does not seem much hotter than normal (50mhz)
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What are you intending to run that will benefit from the overclock? It isn't as if the FPU is used unless an application is compiled for it, or uses the maths libraries (for which you can get FPU versions). The latter aren't exactly going to be that fast anyway compared to FPU direct code simply because of the overhead in doing the library call.
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And that is why I asked originally, is there really any befefit. the answer seems to be no.
I guess now I will; try to get the CPU to hit 66mhz or more
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I did run the beachball and it was fine, did it 5 times in a row. Actually the 68882 does not seem much hotter than normal (50mhz)
Then I'd say it's working, but I wouldn't go above 66 unless you are prepared to buy a replacement FPU when you fry it!
You can also get FPU specific versions of Lha and Zip/Unzip etc etc. Have a look on aminet.
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And that is why I asked originally, is there really any befefit. the answer seems to be no.
I guess now I will; try to get the CPU to hit 66mhz or more
The answer is yes, there is a benefit. Programs that are written directly for the 68881/68882 (like the ones I have mentioned) WILL run substantially faster at 66MHz.
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The highest I've seen a 68030 running without issues is ~64MHz. The thing about overclocking is, you are basically going to kill your CPU one day.
Today, people are used to CPU's having a fair degree of headroom in their clock rating and there's always a bigger cooler you can fit. It's also the case people tend to upgrade their processor after just a few years, so they are unlikely to notice any ill effects.
The 68030 isn't from that era. The 68030 was from the era when chips were sold based on their ability to run at the stated speed correctly. You are talking about taking a component that is probably well over a decade old and running it at 32% faster than the speed it is certified to run at. You might get away with it for months or even years, but one day, your system isn't going to start. You might then discover that it still doesn't start when you put it back to the stated speed either.
Considering that spares aren't that easy to come by, is it worth it?
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If you decide to play it safe, then why not settle for 60MHz on both CPU and FPU? That's a 20% speed increase which is substantial. But make sure you keep the CPU and FPU cool, and any other IC's which generate heat.
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I agree completely and understand the risks. 66mhz was as high as I was willing to go, will probably settle at 55 or maybe even 60
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I agree completely and understand the risks. 66mhz was as high as I was willing to go, will probably settle at 55 or maybe even 60
I understand the desire to squeeze more out of your machine but I would advise against, to be honest. Back in the day, I overclocked my old 68040 from 25 to 30MHz (equivalent to your proposed 50 -> 60 MHz). It didn't make a huge difference in terms of performance to be fair and was less stable.
Now I look at it from the point of view of longevity. I'd much rather have a stable system than a slightly faster one.
If I want raw speed for 68K apps, I use UAE. It's pretty much impossible to beat.
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The 68040 is another animal altogether, much hotter CPU. But I agree might just do 55mhz just for the heck of it