Atari TT - FPU Overclock

[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.

[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

PXL_20210118_114139589.jpg

Before results:
Nembench -

PXL_20210118_115510765.jpg

Fractals (run in TT Medium 16 colour mode) -

PXL_20210118_115835985.jpg

Gembench -

PXL_20210118_120631172.jpg

After results:
Nembench -

PXL_20210118_124533321.jpg

Fractals (run in TT Medium 16 colour mode) -

PXL_20210118_124320415.jpg

Gembench -

PXL_20210118_124757721.jpg

[Icky]

@Steve - nice :thumbup:

Reminds me I have to do this to the TT I am restoring / upgrading.

[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).

[exxos]

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

[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?

[exxos]

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.

[Steve]

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.

[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.

[mrbombermillzy]

I was actually looking at the viability on a TT. And even then, in a very non standard way.