Subject: Re: Utility chip sio's on 4xx (more stories)
To: Michael Smith <>
From: Jason Thorpe <>
List: port-hp300
Date: 03/20/1997 19:47:00
On Fri, 21 Mar 1997 14:03:46 +1030 (CST) 
 Michael Smith <> wrote:

 > It may also control interrupts from the ISA port, but the high 4 bits
 > in the byte at 0xe0 are definitely the interrupt enable bits for the
 > Frodo onboard UARTs.  It wouldn't actually surprise me all that much
 > if all of the IRQ lines on the ISA slot were tied together, so you'd
 > only need one interrupt input somewhere. far as I know, that is how it works... the sio's are probably
at the top 4 IRQs.

 > Hmm, on the 425 it's at scode 12; still, that implies that it's in
 > "real" dio space, and should behave like a normal DIO device.  Any
 > docco for that?

...not that I can find.  As far as I know, it was never documented publicly.

 > There are some other issues here that may seriously affect the
 > performance of such a driver though; the indirection necessary to
 > handle both I/O mapped and memory mapped registers, as well as the
 > different spacing (the dca in the 300's is spaced on alternate bytes,
 > in the 700 they're packed, and the apci ports appear to be spaced one
 > byte per longword) will be expensive, which may be significant on
 > slower systems.'s all memory-mapped on the hp300.  We've already dealt with these
issues... it's called "bus.h" :-)

 > I wouldn't bother with the mouse as a seperate device; the data from the
 > mouse is part of the keyboard data stream; use the same major and a
 > different minor to select between the two.

..this is the model attaches the mouse as a logical child of the keyboard.
It's mainly a place where "mouse" events are collected (for the benefit
of an X server).

 > > (BTW, any locals want to help me replace the LANCE on this 425?  Dave?
 > > I'll buy the first round... :-)
 > Hmm, if you were local I'd say bring it on over and do it here, but
 > until/unless someone headhunts me that's going to be tough. 8(, more reasons to visit Australia!  :-)  (Off topic, but are you
near Melbourne?)

Jason R. Thorpe                             
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