Bus arbitration on the UNIX pc expansion slots, what's correct?

[Lenny Tropiano]

Ok, let's settle this one in my brain ...   What's correct?  
According the the AT&T UNIX pc Technical Reference Manual (pp. 1-19 to 1-20)
the priority levels go like so:

	Priority
	Level			Device

	6 (highest) 		Refresh	
	5 			Expansion slot 1
	4 			Disk interface hard and floppy
	3 			Expansion slot 2
	2 			Expansion slot 3
	1 (lowest) 		68010 CPU

Ok... fine, this is what I've always thought.   Now according to the
AT&T UNIX PC s4bus Specifications [issue 3] (p. 31)

	Priority
	Level			Device

	6 (highest) 		On-board Disk DMA, highest priority
	5 			On-board Refresh Controller
	4 			Expansion slot 3
	3 			Expansion slot 2
	2 			Expansion slot 1
	1 (lowest) 		68010 CPU, lowest priority

For reference, the slots are numbered like so (looking from the back):

+-----------------------+-----------------------+-----------------------+
|        SLOT 1         |         SLOT 2        |         SLOT 3        |
+-----------------------+-----------------------+-----------------------+

Now in practice, Gil noticed tonight when his machine was calling me that
his Telebit Trailblazer throughput was terrible.   (It was bursts of data
separated by long periods of nothing-ness...)   He was running a tape backup
on the system at the same time.  His machine (limbic) and mine are configured 
with EIA/RAM card (tty001=modem) in slot 1, Voice Power in slot 2, and tape
controller in slot 3.   For some reason he and I think that the
bus arbitration layout from the s4bus specs is correct, and the DMA and
I/O requests on the tape were just killing the machine!  

As far as location of the modem port, I was told that tty001 was better
than tty000 because it had priority over the internal port... 

If this is true should one swap the location of the EIA and tape controller?
What happens when I get my expansion box and starlan cards next week and 
I have 5 more slots.  Should I put the repeater card in the highest 
priority slot (whatever that is...)?   

-Lenny
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