Ethernet Cards

[Lyle Seaman]

tmh at bigfoot.FOKUS.GMD.DBP.DE (Thomas Hoberg) writes:

>In article <707 at denwa.uucp>, jimmy at denwa.info.com (Jim Gottlieb) writes:
>|> 6386E WGS).  We switched to the 3Com 3C503 and all was fine.  Our video
>|> card (Olivetti supplied) doesn't have the option to switch it into
>|> 8-bit mode.  I wonder if the 16-bit Ethercard Plus would have worked.

You don't need to have an option to switch a 16-bit board into 8-bit mode,
just put it in an 8-bit slot.

>I really wonder whether there is any advantage to using a 16-bit Ethernet card
>then, other than having a couple more IRQ lines available. The WD Ethercards
>use only a 16k window and I guess nobody could afford to waste 128k of address
>space for that. In any case the bandwidth provided by an 8-bit slot should be
>quite sufficient for a 10Mb Ethernet.

I can't understand why you can't give up 128k of address space, unless your
machine is maxed out on RAM.  Most machines have limits at 16M, and 128K 
isn't a whole lot, compared to that.

I don't know what the bandwidth of the PC bus is, but it's not as simple
as you think.  To keep an Ethernet card pushing data out at 10Mb/s, you
can either 1. keep the bus running at 10Mb/s constantly, or 2. blast
data across the bus occasionally, buffer it on the card, and dribble it
out at 10Mb/s.  Doing (1) is pretty difficult (impossible), so you have
to resort to (2).  That's what a 16-bit card with extra RAM does for you.

Furthermore, it's doubtful that the older cards would be able to get data
out at 10Mb/s even under condition (1).

-- 
Lyle                      Wang             lws at comm.wang.com
508 967 2322         Lowell, MA, USA       uunet!comm.wang.com!lws
             The scum always rises to the top.