From: Tom.Jennings@f111.n125.z1.FIDONET.ORG (Tom Jennings)
Date: Fri, 13 Nov 92 19:23:25 PST
To: cypherpunks@toad.com
Subject: re: Rander box and other stuff
Message-ID: <3612.2B045BBD@fidogate.FIDONET.ORG>
MIME-Version: 1.0
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 U> From: crunch@netcom.com (John Draper)

 U>    I think I have a rough description of the hardware 
 U> serial random generator I want to build.    I want to call 
 U> it the "Rander box" for lack of a better name. 

Using serial ports is probably not a good idea on PC clones. The IBM
hardware design limits a machine to two ports comfortably, four
practical maximum. Any machine that uses telecomm. (BBSs, etc) will
have to consume the serial hardware, and will interfere with whatever
you have to do.

A good choice would be a parallel port, ie. a printer port. The IBM
design allows 4 or more easily, and rarely do you see a pclone with
more than two printers attached. If there isn't a spare port
available, Fry's sells printer adapters for $19.95. Late-model printer
adapters are 8 bit in and out, and are capable of Ethernet speeds.
The parallel port uses standard busy/done and TTL levels.

(For a "universal" serial version, you could internally have the 8 bit
busy/done interface drive a UART. I bet simply fixing the data rate
to 9600 baud would work.)

 U>    When switched on,   and a "cr" (or some other 
 U> character) is sent to it, random bytes will stream out 
 U> continiously.   Another "cr" will stop the byte stream.    
 U> At least this is ONE approach.   If anyone can think of a 
 U> better way,  Pse speak up. 

I was about to say "prolly not necessary", but others make valid
points... XON/XOFF, DTR, etc are all workable... DTR is compat
w/serial and parallel too.

On a pclone, producing bits continuously is easier. When not in use,
the driver will dump bits onto the floor. Fancy (software) drivers
could spool the bits into a nice big pile ("every bit is sacred...").
A simple driver could simply have say 10,000 bits, and continuously
overwrite the oldest (wrap around the buffer...)

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