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Re: Not enough slots!
In article <SKNKWRKS.93Nov8160455@mayall.cs.unlv.edu>,
Scott Alfter <sknkwrks@mayall.cs.unlv.edu> wrote:
>In article <cJwmcc3w165w@ersys.edmonton.ab.ca> herbertf@ersys.edmonton.ab.ca (Herbert Fung) writes:
>>Hmm... I wonder, how realistic is it to construct a sort of switchbox for
>>peripheral cards? Would it be safe? It'd certainly be convienient, one of
>>my GS's has run out of slots and now I'm using a second one.
>
>It's been done before...a company called SCRG had a switchbox with 4
>slots. I think you could only switch cards when the computer was off
>and you could only use relatively slow cards (no disk controllers,
>etc.), but if you needed more slots, it would do the job. They also
>sold an extension cable that would run a slot outside your machine;
>you could then plug and unplug cards as needed without opening the
>machine. (This, I think, would work with faster cards.)
Of course, someone COULD design a box that was more than just a mechanical
type of switching device. It'd probably need a separate power supply to
releave the computer's supply, but all the cards could be powered up and
operational at the same time the rest of the computer is online, and then
there'd just be buffering circuitry to control which card was actually
logically 'mapped' into the slot at any given time. The box could even be
controlled from the computer by adding a few softswitches somewhere. It'd
be preferable to have the box mount right on top of or behind the computer in
order to minimize buss cable length. One would also have to be picky about
what cards they put in it, since DMA cards, etc, wouldn't be happy not having
access to the computer when they want it! Interrupts would be a problem too.
I began thinking about this when I ran out of slots on my //e and wanted to
make a D/A board and some other stuff for it. I have designed an external
box that is addressed from the buss, but I pretty much dropped the Apple II
buss design from there. I've designed it to allow big (almost motherboard
sized) add on cards and be able to address them seperately in different modes.
I've designed a 16 channel 8-bit digital I/O (giving me 128 bits, or the
ability to represent any number from 0 to 3.402823665...x10^38 EXACTLY in
binary format! =) I've also designed an 8 channel 8 bit d/a and a/d board
(that will also support 12 bits by using a different chip to populate it) that
I just have to route a couple more lines to complete! I just haven't had time
to do it. Then of course I still have to expose and etch and populate these
@#$% boards, and the thought of doing so without plated through holes doesn't
appeal to me. Oh well, enough of my plans...
>
> _/_ Scott Alfter (sknkwrks@cs.unlv.edu) Ask me about SoftDAC--digital
> / v \ Call the Skunk Works BBS today! audio for your Apple IIe/IIc!
>(IIGS( (702) 894-9619 300-14400 V.32bis 1:209/263 Apple II, IBM, Trek, & more
> \_^_/ ---===#### Why be politically correct when you can be RIGHT? ####===-
Michael Foegelle
--
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