Clockpatch v4.2 on 25Mhz

[nemox]

hi, i installed this patch, but unfortunately at 25 mhz when accessing scsi frozen, it was an attempt to replace the existing phantom patch. To prevent the falcon from freezing when accessing scsi, it is enough to put a phantom patch on the fpu/sdma route, but it's not perfect, still errors, treecheck 10 errors per 10000 files. My question is, will there still be a delay plate for debugging the sdma? Thank you sorry for my english

[nemox]

One more note, this only happens with the CT60, in 030 mode everything is ok.

[exxos]

There is no delay option on the 4.2.

But 25MHz isn't guaranteed on any Falcons without endless trial and error, it is very hit and miss as the timings are so tight. I suggest you downclock to maybe 20Mhz and save yourself a bunch of headaches.

[Steve]

The v4.2 isn't suitable for bus boosters, you need the V2/V3 which has the SDMA delay similar to the phantom: https://www.exxosforum.co.uk/atari/store2/#0073

I use the V2/3 on my bus boosted falcon with no problems, SCSI works perfectly.

[mikro]

@Steve please refresh my memory -- why did you replace the Phantom clock patch (which is kindly shared by you on PCBWay) with this one? Did it solve more issues for you?

[exxos]

I don't think what clock patch is used with phantom is the key issue exactly. It's all down to tollerences of the falcon. What patch works seems just a fluke down to tollerences also.

You could build 100 patches and some would work and others wouldn't. Your working down to like 1ns timings. Some falcons may tolerate a wider range of patches. Others won't. I wrote a lot of text explain all this already.

When I ran nemesis in the 90s, my falcon would run for weeks just fine then 25mhz would be completely unstable. I mostly just used 20mhz in the end. Later I took it out as a lot programs wouldn't work with it. The video would get messed up.

It seems the norm.... Falcon won't run at 25mhz... Start randomly changing stuff in the hope it ultimately works. What falcon likes what clock patch is down to the the gods with a boosted bus. Also why I suggested my patches are not supported as it's just a huge headache I don't want and a clock patch can't really solve a falcon which simply won't work at 25mhz.

[Steve]

@mikro because I'm the resident bus-boosted-falcon user here on the exxos forum, I've extensively tested all of exxos's various different clock patches over the years and provided feedback. So when testing the V2/V3 (V3 has an even longer delay option over the V2, but in my testing the longer delay didn't change the performance or compatibility over the regular phantom delay time) Anyways I tested so many clock patch configurations I wore the traces out on my Falcon :) In my testing the V2/V3 has the same level of compatibility as the normal Phantom clock patch, but it also improves on the clock signal by reducing ringing. So in my humble opinion, Exxos V2/3 clock patch is the de-facto standard for bus boosted Falcons because it's got a better form-factor, easier installation, not requiring a custom sdma clock wire. For all these reasons I keep the Exxos patch in my system.

If I were using a stock Falcon, my choice would be the v4 series of clock patches. The signal clean-up the v4 produces is absolutely stunning with perfect logic levels, no signal skew, it looks absolutely beautiful on an oscilloscope. But since the v4 design doesn't support clock delay, it isn't suitable for bus-boosted falcons. So for bus boosted: v2/v3, for stock: v4.

[nemox]

after installing a 100pF to the FPU and a series resistor before the SDMA clock input, an extra wire is no longer needed to guide the clock to SDMA. I experimented with various resistive, capacitive terminations, with no significant improvement, now the Falcon is in a state of new path in 4.2 is removed, and the phantom path is returned, with the fpu and SDMA clocked together via an extra delay line, originally for solo wire. I'll still test some adjustable delay fields for SDMA and if there are still errors on SCSI, I'll lower the clock speed, but it's interesting that in mode 030 the scsi is at 25 at high graphics load, absolutely ok, only in mode ct60 there are errors.

[Steve]

Where are you located I wonder? I might have a spare clock patch you can try.

[nemox]

that would be great, I have another falcon, it has other problems. But I bought BlueSCSI and the problems started, because I haven't used SCSI until now.
Im from
Pilsen, Czech rep.
Thanks