Search found 90 matches

by ijor
Fri Dec 07, 2018 3:58 pm
Forum: ALPHA DEVELOPMENT INFO
Topic: 32Mhz oscillator "issue"
Replies: 19
Views: 3468

Re: 32Mhz oscillator "issue"

I added code to my demo shell that detects the speed of the CPU accurately. It's a small loop running on the CPU increasing a counter until an MFP timer interrupts it - and from that counter you can then easily see how fast the CPU is. This counter has shown the exact same values on every computer ...
by ijor
Fri Dec 07, 2018 3:44 pm
Forum: ALPHA DEVELOPMENT INFO
Topic: 32Mhz oscillator "issue"
Replies: 19
Views: 3468

Re: 32Mhz oscillator "issue"

Hmm, what's the accuracy of the original oscillators in the ST? Oscillators usually also deviate from the nominal value with time and temperature, but all the fullscreen demos I've tested on my now 30+ years old ST machines still work fine. How much can the oscillators deviate from the nominal valu...
by ijor
Fri Dec 07, 2018 2:57 pm
Forum: HARDWARE ISSUES
Topic: MPF F11W floppy write protect issue (STE)
Replies: 12
Views: 2188

Re: MPF F11W floppy write protect issue (STE)

I was having read issues, also write issues hence the corrupt desktop.inf file causing chaos on my desktop, obviously different issue then WP signal not working correctly as the write happend. oh, I see. I would assume read issues would have been partly fixed by CRC checks. Though I never looked in...
by ijor
Fri Dec 07, 2018 1:53 pm
Forum: HARDWARE ISSUES
Topic: MPF F11W floppy write protect issue (STE)
Replies: 12
Views: 2188

Re: MPF F11W floppy write protect issue (STE)

The WP signal is set on bit 7 of the status register. So when TOS reads it, it sees a false WP signal because of ringing on the bus.. Not bit 7, bit 6. But yes, TOS could see a false wprot error when reading the status register. But if so you would expect general floppy malfunction. Even if ringing...
by ijor
Fri Dec 07, 2018 1:35 pm
Forum: HARDWARE ISSUES
Topic: MPF F11W floppy write protect issue (STE)
Replies: 12
Views: 2188

Re: MPF F11W floppy write protect issue (STE)

I'm not sure I see the relation between ringing at the FDC data bus and a write protect error. Obviously it could create all sort of problems. And might be it is more critical when writing and hence format fails. But it shouldn't precisely produce a write protect error unless actually it doesn't, ma...
by ijor
Fri Dec 07, 2018 12:05 pm
Forum: HARDWARE DISCUSSIONS
Topic: Project: HDMI/DVI out for STFM
Replies: 526
Views: 67204

Re: Project: HDMI/DVI out for STFM

So it is a powering issue indeed. Too bad Smonson can't yet reproduce it. I still don't see however, how glitches, ringing, or gnd noise would produce the exact symptoms we see. According to the tests, at least for some of the readings, the bidirectional level shifter is not driving the bus at all. ...
by ijor
Wed Dec 05, 2018 6:31 pm
Forum: HARDWARE DISCUSSIONS
Topic: Project: HDMI/DVI out for STFM
Replies: 526
Views: 67204

Re: Project: HDMI/DVI out for STFM

On a second thought ... this should be just a short glitch, right? Say, a few nanoseconds? Then eventually FDIR has to rise before the cycle ends. So it doesn't match exactly the behavior ... Still, gnd bounce might produce all sort of ill effects I guess. Edit: In any case, it might be important to...
by ijor
Wed Dec 05, 2018 6:19 pm
Forum: HARDWARE DISCUSSIONS
Topic: Project: HDMI/DVI out for STFM
Replies: 526
Views: 67204

Re: Project: HDMI/DVI out for STFM

Just another (probably crazy) idea: On a different plug-in board that I recently worked on, there was a big problem with ground bounce. Modern, very fast CMOS output drivers can inject a short but intense burst of current into ground while switching logic levels. Combined with the inevitable induct...
by ijor
Wed Dec 05, 2018 6:10 pm
Forum: HARDWARE DISCUSSIONS
Topic: Project: HDMI/DVI out for STFM
Replies: 526
Views: 67204

Re: Project: HDMI/DVI out for STFM

It's the classic setting of the screen start address outside of physical RAM. Usually you see noise, but in fact that noise is the bus activity. If you do that in a fullscreen, the noise is just a static pattern because all activity is synchronized. Ok, that effect doesn't depend on Shifter. It's s...
by ijor
Wed Dec 05, 2018 2:14 pm
Forum: HARDWARE DISCUSSIONS
Topic: Project: HDMI/DVI out for STFM
Replies: 526
Views: 67204

Re: Project: HDMI/DVI out for STFM

One thing I'm not following, is if there is a drive problem on D9, why would it work on some boards but not other? Well, I don't know for sure of course. It doesn't seem to depend on the chipset. It doesn't seem to be a timing issue. It could be a functional issue, such as a bug in the Verilog code...

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