🚀 go-pugleaf

	(Please use e-mail to reply.)

	Greetings.

	This message is for people who remember S100 buss and can,
	perhaps, give me it's advantages and disadvantages, for a
	particular application, as compared with the AT ISA, Multibus
	and QBus. If not interested, hit "n" now. 



	

	I am in the process of planning a small IBM AT add-on. 
	It will have it's own case and be connected to the AT-buss 
	though an interface card.

	The reason why I don't want to put it on one board (or a set)
	Is that it's components are big real-estate users. Most of 
	the stuff will be "custom", basicly a lot of PLAs and such. 
	Also, a lot of "discrete" LSI and SSI. It also has to be 
	expendable in a big way.

	My question is really on the buss connctors and layout.

	I would like to use the S100 for a number of reasons:
	
	1) It's well known and relatively reliable (and cheap)
	2) Lot's of people have S100-based enclosures
	3) There are a lot of pins available (lot's of possible grounds)
	4) wire-wrap boards go for ~$25 each.
	5) The idea of having an on-board voltage regulator is
	   a good idea in systems that run fast and don't like
	   noise in DC supply.
	
	Perhaps a little info on what the buss has to handle will
	help in your criticizms :-)

	I already have a 386 (33MHz) but am not impressed with the
	way the power of the cpu is bogged down, to a standstill, by
	the use of the ISA buss (AT buss) I can't really do much about
	it, but I _can_ do something about the way I add more features
	to my system.

	I want to have lots of digital inputs (8255s) and analog 
	channels. I also want a way to design my own projects (such
	as coprocessors, controllers, etc.) I have been told, by 
	people I consider gurus, that such things do not belong 
	on the system buss. They belong in their own "realm" to 
	which the system downloads problems, goes back to it's main 
	job, and only returns to transfer the processed data back to 
	main memory. 

	Back to the question:

	I don't want people to misunderstand me. I'm not trying to
	use an existing buss from the compatibility point of view.
	All the pins in my S100 project will be my very own. What I
	want is a reliable and proven array of connectors, pin
	spacings, noise problems, proto-boards, and other matters
	which make the final system reliable.

	So, can anyone suggest a better "card cage"? I was looking
	at the Multibus I and II, but they are much too expensive.
	The card cage also is hard to come by. I have also looked
	at the QBus, but finding proto-card can be an adventure.
	And, last but least :-), there is the original AT connector
	and wire-wrap board. The only problem is that it's small, 
	compared to the above board, and has many less pins. Not 
	that I plan to use them all. I want at least 20 or so for 
	grounds and, with the AT connector, there aren't that many left.
	
	One more thing, I want the buss to be able to handle fast
	clocks on parts of it. That is, there may be a set of
	pins that operate at a high speed, compared to the rest, without
	interference. I plan to use the "not used" pins, on the opposite
	side of the card-edge, as grounds.  

	One thing though, why _did_ the S100 buss die? If IBM used
	the S100, would it be the most popular "standard" now?
	Or was(is) something just _wrong_ with it?

	Take care.

	P.S. Please don't just say "You're an idiot, stick with NuBus"
	or the like. I would like people to give me "reasonable" comments.
	Also, please e-mail. I will archive and make it available.
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