At 11:17 AM -0500 12/22/00, Allen Briggs wrote:
> > What do macs use as far as a UART chip on their serial ports?
>
>AMD 8530.  This has a fixed 3-byte FIFO.  Some of the "newer" macs
>have an extended version of this chip that does have a deeper FIFO,
>but IIRC, we don't detect and use that.  That would probably help,
>if we need to explicitly support it.  DMA on the IIfx, Q900, Q950,
>AWS95, Q/C660, Q840 would be nice, too.

It was originally a Zilog chip designed to mate with the Z80 --- 
which is where I learned to program it.  I think it could be 
assembling a fourth character while it had 3 complete in the FIFO, 
because the documentation I read called it a 4-byte FIFO.  I haven't 
looked at it in more than 10 years you understand.

It shouldn't require any special code to support a deeper FIFO 
because I think the status flag/interrupt was just on Tx empty and on 
Rx available.  Then there was an error flag/interrupt for receive 
FIFO overflow, but no indication anywhere about the fill level of the 
FIFO.


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