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Re: Atari TT - FPU Overclock
Posted: Thu Jan 03, 2019 9:27 pm
by Steve
Ah thanks for going to all the trouble of checking
I am guessing that an overclocked FPU might help speed up some tasks in Netbsd since an FPU is required for that OS, I wonder what software use it or whether they just require an FPU as the base requirements for all possible types of calculations.
Re: Atari TT - FPU Overclock
Posted: Mon Jan 18, 2021 6:47 pm
by Steve
Hi Icky, today I finally got around to making this little overclocker for my TT FPU. I used a 48mhz Osc. Thanks again for the instructions, I have before/after benchmarks below:
My version:
- PXL_20210118_114122776.jpg (547.59 KiB) Viewed 3009 times
- PXL_20210118_114139589.jpg (415.14 KiB) Viewed 3009 times
Before results:
Nembench -
- PXL_20210118_115510765.jpg (559.88 KiB) Viewed 3009 times
Fractals (run in TT Medium 16 colour mode) -
- PXL_20210118_115835985.jpg (404.67 KiB) Viewed 3009 times
Gembench -
- PXL_20210118_120631172.jpg (573.75 KiB) Viewed 3009 times
After results:
Nembench -
- PXL_20210118_124533321.jpg (481.49 KiB) Viewed 3009 times
Fractals (run in TT Medium 16 colour mode) -
- PXL_20210118_124320415.jpg (393.4 KiB) Viewed 3009 times
Gembench -
- PXL_20210118_124757721.jpg (508.25 KiB) Viewed 3009 times
Re: Atari TT - FPU Overclock
Posted: Mon Jan 18, 2021 7:01 pm
by Icky
@Steve - nice
Reminds me I have to do this to the TT I am restoring / upgrading.
Re: Atari TT - FPU Overclock
Posted: Mon Jan 18, 2021 8:53 pm
by mrbombermillzy
Hey, I just wondered if any of you guys actually tried running up the FPU past 48Mhz? Does the IC run hot at 48?
(As an aside, I did some FPU tests a while ago and if the chip can run 64Mhz (or more!) then there may be a possibility for it actually being useful for non FPU tasks (extended MOVEs instead of or interleaved with the 030).
Re: Atari TT - FPU Overclock
Posted: Mon Jan 18, 2021 9:09 pm
by exxos
mrbombermillzy wrote: ↑Mon Jan 18, 2021 8:53 pm
Hey, I just wondered if any of you guys actually tried running up the FPU past 48Mhz? Does the IC run hot at 48?
https://www.exxosforum.co.uk/atari/last/FPU/index.htm
Re: Atari TT - FPU Overclock
Posted: Mon Jan 18, 2021 9:14 pm
by mrbombermillzy
Thanks Chris.
So, thats up to 64Mhz stable really and with no added cooling? Interesting.
I wonder what a HS and even a fan could do for that figure?
Re: Atari TT - FPU Overclock
Posted: Mon Jan 18, 2021 9:20 pm
by exxos
mrbombermillzy wrote: ↑Mon Jan 18, 2021 9:14 pm
So, thats up to 64Mhz stable really and with no added cooling? Interesting.
I wonder what a HS and even a fan could do for that figure?
Yep... I don't think any cooling will help, I don't think it got hot even, but cant say exactly as was some years ago now.
Re: Atari TT - FPU Overclock
Posted: Mon Jan 18, 2021 9:30 pm
by Steve
mrbombermillzy wrote: ↑Mon Jan 18, 2021 9:14 pm
Thanks Chris.
So, thats up to 64Mhz stable really and with no added cooling? Interesting.
I wonder what a HS and even a fan could do for that figure?
Yes but notice the times:
32mhz MB clock - 46.115 seconds
50mhz oscillator - 44.98 seconds
64mhz oscillator - 44.70 seconds
No point running at just-about-to-crash-and-burn 64mhz speed, when it only gives a tiny increase in speed, see the diminishing returns? So this is why people are using 48mhz as it is the safest and quickest before diminishing returns.
Re: Atari TT - FPU Overclock
Posted: Mon Jan 18, 2021 10:15 pm
by exxos
The tests were on the falcon with 16mhz bus. If the bus fas faster then a higher clock speed may be benifitial.. But it does start to get a bit pointless past 50mhz otherwise.
Re: Atari TT - FPU Overclock
Posted: Mon Jan 18, 2021 11:55 pm
by mrbombermillzy
I was actually looking at the viability on a TT. And even then, in a very non standard way.