lenny@icus.islp.ny.us (Lenny Tropiano) (10/04/89)
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 -- | Lenny Tropiano ICUS Software Systems [w] +1 (516) 589-7930 | | lenny@icus.islp.ny.us Telex; 154232428 ICUS [h] +1 (516) 968-8576 | | {ames,pacbell,decuac,hombre,talcott,sbcs}!icus!lenny attmail!icus!lenny | +------- ICUS Software Systems -- PO Box 1; Islip Terrace, NY 11752 -------+