Falcon FPU overclock PCB

[marbosar77]

Thanks @mikro @stephen_usher @HigashiJun for your feedback and advice.
Anyway I think I'll replace rtc, overclock fpu and dsp, and install clock buffer patch. All the job will be done by a much more expert person than me. If something goes wrong, then we will revert to stock condition.
About the latter mod... I have the V3 board, so I need to start from the "EXXOS CLOCK PATCH V2 & V3 INSTALL GUIDE" chapter and then follow "V2 & V3 MANDATORY MODIFICATION", but there is something I don't quite understand.
It seems that a modification to the Falcon needs to be done and shown at https://exxosforum.co.uk/atari/last/fal ... htm#RESMOD, but this link shows an older patch which finally leads to a 3rd method with buffer resistors and from there it starts to explain all the stuff related to THE FINAL FALCON CLOCK PATCH INVESTIGATION 2022, where V2 and V4 patches are shown.
I mean, my guess is that I NEED to follow all the instructions on "EXXOS CLOCK PATCH V2 & V3 INSTALL GUIDE" and "V2 & V3 MANDATORY MODIFICATION" chapters, but where is the other supposed modification shown here (https://exxosforum.co.uk/atari/last/fal ... htm#RESMOD) that I should do? It is completely obscure to me.

[HigashiJun]

@marbosar77

If you have the V3 board, then solder it on the U63 IC chip.

Solder the provided lead on the V3 board according to the pictures in exxos' how-to (4 points to solder).

Remove R216, R221 and R222 resistors and solder the 4 leads from the board to where you removed the resistors and according to the pcitures in the how-to.

Apply the mandatory modification for the V3 board:

DSCN3718.JPG

The solution is in the image which shows a simple 0805 or 1/8 watt leaded 100K resistor which is soldered on the "bootleg" track. The white wire connects to 0V as shown.

And you should be done.

[marbosar77]

@HigashiJun

:thanksyellow:

[marbosar77]

Hello again guys, sorry if I resume this post.
Recently I have found this oscillator: https://centuriontech.eu/product/crysta ... frequency/. It is a HCMOS type.
Based on your experience, would it be safe to use this for FPU/DSP overclocking, instead of a common CMOS type?

[HigashiJun]

I don't think it will hurt your machine if you try.

And if it works, then should be good.

[marbosar77]

Thanks @HigashiJun , I imagine that "H" stands for "high speed" (shorter latency?) and nothing more @exxos .

[exxos]

I've not had time to follow all the topics sorry. But why not just buy the proper stuff from the store ?

https://www.exxosforum.co.uk/atari/store2/#0246
https://www.exxosforum.co.uk/atari/store2/#0201
https://www.exxosforum.co.uk/atari/store2/#0265

[marbosar77]

Thank you @exxos .
I have already bought the fpu, but it's 40mhz. Is it still reliable enough to perform the 50 mhz mod?
Apologies for having bothered you.

[exxos]

In case of the stock falcon only, the 40mhz FPU might run at 50mhz because it's clock switching between 16/50mhz. But I can't guarantee success as I've not tried it. The speed rating of my FPUs are genuine. A 40mhz FPU will not run at 50mhz constant. I have built a special test DFB1X to verify speeds.

If you need a 40mhz osc I've got some somewhere as they are used in the falcon VGA adapters, t would take some days to find them and add them to the store though.

But if you only want the osc and outside of the UK then its not very cost effective because of the postage. But as the parts are getting hard to find now there might be not much choice. Reputable large companies like mouser still sell a good range of osc.

[marbosar77]

Understood. Centuriontech has a good stock of custom-built osc, maybe I can find a 40mhz one.
I also can assume that, according to what you have described here (https://www.exxosforum.co.uk/atari/last/FPU/index.htm) there would not be appreciable gain between a 40mhz and a 50mhz osc, maybe 0.5-0.6 seconds?
Thank you again for your time, I appreciate it very much.