Date   : Wed, 27 Jul 2005 10:49:49 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: Econet-Ethernet bridge

On Tue, 2005-07-26 at 19:05 +0200, Mark Usher wrote:
> >As long as the design and PCB is well documented, 
> >and available in digital form, surely in umpety years 
> >time when the current chips are have transformed into 
> >unobtanium, it can just be edited to accommodate the 
> >new ones?
> So why bother putting on an ISA slot now, that wouldn't be used as the part
> is available. And as you point out, getting hold of ISA cards in ten years
> might be quite difficult? 

I agree that an ISA slot on the board wouldn't necessarily be much use.
ISA cards are still easy to find now (although it took me a couple of
months to find 20 *identical* boards recently), but that won't be true
in 5 years time.

The bit I'm questioning is the whole "everything on one board" approach
as it negates keeping with the times. The bit you know will stay the
same is the Econet side, because that's the whole point of the project.
But you don't know what the network interface on the other side of
things will be - already someone might want 1Gbit Ethernet because
that's what their LAN is, or token ring, or slip.

Hence the reason I like the idea of interfacing the an Econet module to
a PC, and letting the PC worry about routing and whatever other
hardware's attached (plus things like running as an Econet fileserver if
needs be). The PC hardware can change with the times without redesign of
anything. Note that PC doesn't even mean IBM-compatible; could be a Mac
or a RiscPC or whatever - anything that supports a common OS between the
hardware (hence going for Linux or *BSD would seem sensible, with a
software project fork for those wanting Windows say)

The only critical thing is what interface to use between the Econet
module and the PC. PCI and ISA are probably dead ends for the reason of
changing times as mentioned before. That probably leaves SCSI, USB,
serial and parallel. 

SCSI's not available on enough machines for it to be viable. USB's only
on newer hardware, whilst serial is sometimes only available on older
hardware. Parallel seems to be everywhere, but may well be far too slow
to drive a module.

So, possibly USB or serial are the choices. Maybe both is an option as
at least from a hardware point of view the interface is likely trivial
compared to an all-in-one board with its own CPU. 


I don't know. I can see advantages in both an all-in-one board and a PC-
interface approach. The former's more compact, and more fun for people
to design. The latter's more cost-effective for users and probably more
flexible both now and as time goes on.

At the very least, I'd urge any project to keep details of driving an
Econet module as a seperate area from the rest, as it'd then be valuable
input for anyone trying the other approach...

cheers

Jules