exxos's Atari, Amiga & retro forum

stephen_usher wrote: 16 Feb 2026 12:20 How "slow" is slow? The equivalent of 9600 baud, which is what the output to the serial port is? If so then that's normal.

S - L - O - W lol
see the link above to my dropbox

OK.That is slow. Almost as if there's a timeout waiting for feedback from the MFP that the serial port has sent its data.

stephen_usher wrote: 16 Feb 2026 12:56 OK.That is slow. Almost as if there's a timeout waiting for feedback from the MFP that the serial port has sent its data.

So we agree this is abnormal...but where to start ?
I've run ace invaders and loom on this STe and they both appear to run just fine..
As do the tests themselves (so far) running on the diag cart...once the slow menu display has completed.
I've run floppy tests ..sound tests and Blitter tests without problems ..also the 4mb upgrade was tested and passed.
I'm happy to fault find some more..but no idea where to start with this one.
any advice from those familiar with the STe functionality will be most welcome.
There obviously IS a fault but it isn't affecting overall operation.
In fact ...had I not obtained a diag cart may never have realised that there is still a fault.
rgds

It looks to be possibly a communication problem with the MFP (68901) maybe. If you can make up a serial port loopback cable and run the diag cart test, which you can't do without the loopback cable, might tell you something. The MFP isn't really used for anything else so games etc. won't care if it's not working correctly.

I just watched the video and that is really slow. I tested one of my MSTs and one of my STE's at lunchtime and whilst it's a line at a time, it's quick and takes no more than 3 seconds to load the menu on either system.

What diag cart do you have?

stephen_usher wrote: 16 Feb 2026 13:41 It looks to be possibly a communication problem with the MFP (68901) maybe. If you can make up a serial port loopback cable and run the diag cart test, which you can't do without the loopback cable, might tell you something. The MFP isn't really used for anything else so games etc. won't care if it's not working correctly.

That makes sense to me Stephen..

My STe will most likely function perfectly well without this fixed ..but better to fix it if I can.
I do have some 25pin plugs and sockets ...so maybe I can knock up a loopback dongle ?
would an Amiga dongle work maybe ?

Picture of the diag cart added

I think I might start with continuity testing from all the pins of U203...as it is in this area where 2 of the open circuit traces were found.
The breaks were so small I never actually saw them...so just used bodge wires.
If everything tests as it should I'll be looking into a loop back dongle for serial.

There are plenty of MC68901 avalable out there ..but fitting a 48pin IC base would be a task I wouldn't enjoy.

So the very first test that runs when the diag cart starts and before anything else is "Testing MFP, GLUE timing and video". @stephen_usher may be onto something about it being the MFP as that comes first before the other two.

What happens if you run the same test once the diags are loaded using the T option?

Also for the serial test loopback dongle, this is how mine is wired:


Thats a plug from the full ST Test harness I own and is known good. If your Amiga plug is wired the same then you should be good.

An RS232 loopback is an RS232 loopback really. It may or may not test the modem control lines as well so that wiring could possibly be different.

You guys are great..
First job then ..
I'll make up a dongle like the one jonnie posted up.
cheers
...and from memory after running all internal tests...in fact ANY test..the menu has to load again...at a snails pace.
So not just at boot/first run.