Wierd issue with A4000D and a M1438S

[patrik]

I got a really wierd thing going on with a combination of A4000D and a M1438S multisync monitor.

If I power on or reboot the A4000D with the M1438S powered off it just gurus over and over and thus refuses to boot -  the powerlight flashes and I can see on the diagnostic lights on the Ariadne card in it that it reboots over and over again.

If I then power on the M1438S it will come out of the guru-loop, display a software failure (error 8000000 and task 08003320 if it has loaded all the 3.9 stuff or task 080033C8 if it is 3.1 as on powerup).

If I disconnect the M1438S from the RGB-port or connect something else like the trusty old A520 or a VGA-monitor using the C= VGA-adapter everything works just fine.

I have also tried the M1438S with another completely clean A4000D - C= A3630, kickstart 3.0, no harddrive, no nothing and it is affected too. It doesn't guru repeatedly, it just seems to lock completely just when it is about to show to the kickstart-screen. If I turn the M1438S off and power on the Amiga, it will come so far that it clicks once with the disk-drive, just where it should show the kickstart-screen next but stops there. If I turn on the M1438S it works fine and will after reboot or power on show the kickstart-screen and keep clicking with the disk-drive as normal.

With my A1200 though there seems to be no problems, it boots normally disgregarding if the M1438S is on or off.

Anyone of you who has experienced this or has heard of something similar?


/Patrik

[Thomas]

If I power on or reboot the A4000D with the M1438S powered off it just gurus over and over and thus refuses to boot - the powerlight flashes and I can see on the diagnostic lights on the Ariadne card in it that it reboots over and over again.

This is a known problem. If the monitor is not powered, the Amiga thinks there is a genlock connected and expects an external synch signal. As there is none, it crashes.

The only solution is to switch on the monitor first or to power on both machines from the same switch.

Bye,
Thomas

[patrik]

@Thomas:

Thanks for the help Thomas.

My idea was to use the M1438S as a secondary monitor for software that needs to output via the chipset. As I will not be using it all of time it would be very convenient to be able to keep it switched off.

As the Amiga starts happily with a powered off VGA-monitor connected with a C= VGA-adapter, it feels like making an adapter that does the same thing for the M1438S - buffers the horizontal and vertical sync-signals would prevent this effect.

(edit):

I wired a C= VGA-adapter to the M1438S and it allowed the Amiga to start without the monitor powered on :=).


/Patrik

[Thomas]

Cool :-)

I would have suggested to hot-plug the monitor when needed, although this is probably not recommended. Such an adapter certainly is much metter.

Bye,
Thomas

[Framiga]

sorry Thomas but i don't agree.

The way a genlock is recognized on an Amiga, is totally different. (via the XCLK and XCLKEN)

I have since a life, a 1084 connected to the Amiga RGB port (switched OFF quite always).

@Patrick

the fact that you have no problem with an A520 and/od a VGA adapter, let me think that you have a problem on the Amiga 23pins>1084 cable (a ground loop or something that charge too much the H/V Sync lines)


EDIT- ahhh . . . . understood now.

You had a 23pins>VGA direct cable installed? (without the VGA adapter)

Ok now . .  .as never said :-)

[lordspider]

@Patrick:

I have similar problem: RGB output is connected to the CV64 input with a RGB-VGA cable. I've recently upgraded my A4000D mobo to 3.1 ROMs and after I powered it up, it crashed in a loop.
Similar like you, after I disconnected the cable from RGB port, Amiga started to work without problems.
What's more strange, after installing the old 3.0 ROMs again, the problem disappeared, but if I try to use BlizKick ans a 3.1 ROMs image file, the problem comes back.

Any ideas?

[patrik]

@Framiga:

To clear any confusion:
I have tested two totally differently configured A4000D and one A1200. Both A4000D refuse to boot if the M1438S if powered off, while the A1200 always boots.

The M1438S has a regular 23-pin female DSUB so it doesn't need a VGA-Adapter to be connected to the Amigas.

I tried connecting a VGA-monitor using a C= VGA-adapter and that works fine - the A4000D starts disregarding if the monitor is powered on or off.

I also hooked up the M1438S to the A4000D via a C= VGA-adapter using some quick and ugly wiring . This worked fine and the A4000D now booted disregarding if the monitor was powered on or off, just like with the VGA-monitor.

So atleast this M1438S, when it is powered off, draws too much current on the H/V-sync lines for the A4000D's taste, apparently not too much for the A1200 though, so it seems like the load is on the hairy edge. Both the monitor and its cable are in very good condition so it doesn't feel like it should have a ground-loop. Who knows, maybe this model wasn't really tested very well with the A4000D? I have read that the original Microvitec version of this monitor was often shipped with a HDSUB15 connector  on its cable plus a VGA-adapter...

Anyhow, I will definately make an adapter for it that buffers the H/V-sync lines .

(edit):

The guy who made this description also claims that the Amiga thinks there is a genlock attached if the H/V-sync lines are loaded too much.


@lordspider:

My testing "kindof" gave results similar with the second A4000D (Kickstart 3.0). With a WarpEngine fitted, it managed to softkick Kickstart 3.1 from the harddrive, but crashed on the next boot (with Kickstart 3.1).

Though, I never tried this A4000D with a harddrive and the stock C= A3630 card, but it locked after one click with the diskdrive, just when it was about to show the bootscreen, so it doesn't seem to work flawlessly with Kickstart 3.0 and too much load on the H/V-sync lines either.

That RGB-VGA cable of yours, does it buffer the H/V-sync lines? If not, I bet that would do the trick.

(edit):

Here you will find info on how to make a buffered one.


/Patrik

[Framiga]

ok understood now.

Its enough, to clone the Commodore VGA converter using a double inverter/trigger (its not really a buffer, it decople/trigger the H/V lines)

You said also that there are no problems with the A1200 . . . i didn't know, thanks :-)

[X-ray]

@ Patrik

I have the same 'feature' here. Right from out of the box my A4000T would not boot if the M1438s was connected but not switched on. Still true today. It repeatedly gurus.

[patrik]

@X-ray:

I finally pulled my thumb out of my arse and made a proper HDDSUB15->DSUB23 adapter cable today. This means that the M1438S can now be connected to a normal VGA connector and can thus be connected to the A4000 via a C= VGA adapter which enables the A4000 to boot when the M1438S is switched off :=).


/Patrik