You can use any connector which suits you. You can use any name for a bus,
even Fred or Jake. You can use any existing bus protocol you desire. It's
your computer.
What I said, apparently not clearly enough, is that I'm partial to the VME,
and, though the typical wire-wrap connector for VME (i.e. that particular
connector, VME or not) costs more than a typical PC at the junk store. I
made the mistake of believing that, from your prior comments in other
context, you watch every penny with considerable interest, and you might
appreciate the opportunity to use a video board, perhaps a Mono, or a VGA,
or even HGA, none of which use interrupts or DMA. For that reason I figured
you'd not mind corrupting the "standard" usage of ISA signals since you'd
not be using circuits which use the ones which you felt were inappropriately
implemented. I said that because if you go dumpster diving in almost any
business park or office complex, you'll find ISA serial cards and ISA video
cards, particularly on a Monday or a Friday.
OTOH, if dumpsters are not to your taste, the thrift stores sell them for
the approximate cost of a burger here in the US. You can get LAN boards and
others there too, but they sometimes use interrupts and DMA, which might be
a problem if you've changed the way in which you use them from what a
typical PC does.
In my view, and that's not universal, by any means, $2 VME cards don't come
up often enough for me ever to have seen one. If you like VME and find them
to be cheap enough, I think that's an excellent choice, not that my approval
is needed for what goes in YOUR computer.
I did say, however, that if I were going to switch to the 96-pin DIN 41612
connector, I'd use VME because that gives me a fallback position if I
haven't time, patience, or skill enough to create my own ??? and I don't
mind shelling out the $$$.
I can guarantee you, though, that if you build your own serial card for
whatever bus, it will cost more for the parts than an ISA video card at the
thrift store would cost. Maybe, if you intend to roll your own, you SHOULD
build an ISA adapter or two, so you can save the time and trouble, not to
mention expense, of building a card you can buy for little money. That way
you can allocate your scarce resources in the way which best serves your
goals and build your own video board, or whatever, later.
If you were to choose to reinvent the ISA on a better connector, being short
a couple of pins, you could quickly do away with the 4x Color-burst
oscillator and the AEN signal, neither of which would do much four you
outside the PC.
regards,
Dick
-----Original Message-----
From: Tony Duell <ard_at_p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Monday, July 05, 1999 2:14 PM
Subject: Re: OT: A call to arms (sort of)
>>
>> On Sun, 4 Jul 1999, Richard Erlacher wrote:
>> >If I were using the DIN connectors, I'd get a standard out, read and
>> >understand it, and then use it, calling it VME, its rightful name.
>> >Unfortunately, I'd not be able to get a two-port serial board or a LAN
board
>> >for VME from the local thrift store.
>>
>> I don't get it...are you saying that the connector somehow determines the
>> bus? An bus could in theory be compatible with ISA and use some other
>> connector, and still be ISA for the most part.
>
>Exactly. A 3-row DIN 41612 connector has 96 pins. ISA bus has 98 pins (on
>a 16 bit slot). And I'm sure I could find 2 signals that I could 'do
>without' (miss off one of the DMA channels?).
>
>In other words you could put something with much the same signals as ISA
>on a DIN41612 if you wanted to. The result shouldn't be called ISA
>(because you can't just plug a card straight in). But it would work, and
>the cards would be easy to design.
>
>I like DIN41612 connectors because you can easily use them on homebrew
>cards. Wire-wrap versions exist. If you want to use a card edge type of
>connector you really have to gold-plate the PCB, and that's hard to do at
>home. It's also a pain having to get a PCB house to make all the
>prototype boards. Much easier if you can homebrew them.
>
>I've used those connectors for all sorts of things, most of them not
>VME-related. Of course I've not called the result VME...
>
>-tony
>
Received on Mon Jul 05 1999 - 17:11:39 BST