Re: OldWorld floppy and serial port work

[David Riley <fraveydank%gmail.com@localhost>]

Actually, my bad... turns out it was the other end of the serial line that's 
the problem. :-)  If I just use a Mini-DIN8->DB9 conversion and run it to a 
*real* serial port on my Windows machine, it behaves; the Keyspan adaptor must 
be having issues (it's been otherwise well-behaved so far, though).  I just 
took the macppc FAQ about the serial ports at its word, and I suppose that's 
what I get.  We might want to update that sometime?

Back to floppy-world... :-)


- Dave


On Jul 8, 2010, at 3:46 PM, Michael wrote:

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> Hello,
> 
> On Jul 8, 2010, at 12:46 PM, David Riley wrote:
> 
>> Well, that's the problem; I have a 9600, which is probably somewhat 
>> different than the serial port on the G4 (which is built in, but not exposed 
>> by default, and I wonder if it's different hardware).  All the way back to 
>> the original Mac, they've used a Z8530 (just like Sun and everyone else who 
>> wanted a *real* serial chip), and mac68k works fine.  For me, if I look at a 
>> man page, it stops responding to serial commands (though it'll still output 
>> log messages, which is puzzling).  The system log doesn't output any debug 
>> info, so I'll probably have to start from the top.
> 
> I would suspect interrupt problems. The G4 has a completely different 
> interrupt controller ( OpenPIC instead of Apple's own ) which should not lose 
> interrupts but Apple's might. If we enable an interrupt line that's already 
> asserted it will not cause an interrupt for example. There is code in place 
> to check this condition, it works fine with other devices but occasionally 
> weird things happen - for example I get lost interrupt messages from the IDE 
> chip on my beige G3 on first access to the disk with no further ill effects. 
> And this does not happen with any other Apple IDE chip so it's probably a 
> Heathrow thing.
> So, first thing I'd do is to run systat 1 vmstat and check if the serial 
> port's interrupts still fire when thinks lock up and you keep sending. Since 
> it happens on a G4 as well it's very likely not the actual interrupt 
> dispatching code but something in the macppc-specific portion of the zs 
> driver. In other words, what Donald Lee said.
> 
> have fun
> Michael
> 
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