choosing base addresses on NICs

[Feldman, Gerry]

First, the 9(?) pin port is called AUI. This is the original Ethernet. The
coax is called a BNC connector. The RJ45 connector is 10baseT. The base
address, as you guessed is the i/o port address. It is important in PC
architecture that each device have its own IRQ and its own I/O port base
address. The PC was not designed for the type of work it is doing now, so
these tend to be severe limitations. Theoretically, it is possible for
multiple devices to share the same IRQ, but the device drivers sharing that
IRQ need to know about this, and need to be able to determine which board
(or port on the board) caused the interrupt. 

Jerry Feldman
Contractor, eInfrastructure Partner Engineering
508-467-4315
Compaq Computer Corp.
200 Forest Street MRO1-3/F1
Marlboro, Ma. 01752


> -----Original Message-----
> From:	pfarrar at learningco.com [SMTP:pfarrar at learningco.com]
> Sent:	Monday, December 27, 1999 1:03 PM
> To:	discuss at Blu.Org
> Subject:	choosing base addresses on NICs
> 
>      Hi,
>      
>      I've never been clear on the base address thing.  And I've spoken
> with 
>      a few others who seemed equally uncertain.  So on all of our
> behalves, 
>      I am posing the following questions.  Any insight would be greatly 
>      appreciated:
>      
>      I have 2 3c509B NICs.  Each has 3 connectors TP, coax and a 9(?)PIN.
> 
>      I need to use the DOS software to configure these to use TP.  No 
>      problem.  But I want to put them both in the same box (for the usual 
>      reason).  So I have to consider IRQ and Base address (I can find the 
>      free IRQs easily enough in /proc/interrupts).  
>      
>      What rational goes into choosing another IRQ/Base Address pair for
> the 
>      second card?  Most cards seem to default to IRQ 10 and 0x300.  Is 
>      there a normal relationship between the IRQ and Base address (like 
>      serial ports and IRQs have)?  Or can I just use any free IRQ/address 
>      combination?  
>      
>      My assumption is that 0x300 is the START of an address range.  How 
>      large is the range?  
>      
>      How does the three byte 0xNNN addressing form relate to the addresses
> 
>      presented in /proc/ioports?  My Linux machines are at home, but my 
>      memory is that the file lists ranges using four byte address names.
>      
>      Also, what is 'full duplex' and do I want it enabled?
>      
>      TIA,
>      Peter
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