I got my hands on a couple of PC boards for what appears to be
the XT project motherboard (MBE-XT) that went by the name of "The Big Blue
Seed" by Ray Kosmic and NuScope Associates. The book I have is an assembly
manual only and has no BIOS source.
Does anyone have this? Interestingly, the assembly manual also
has assembly procedures for a disk controller, memory, video, "super I/O",
miscellaneous, and prototyping. All told, there are 35 cards (3-PC
motherboard, 8-XT motherboard, 6 disk controller, 4 memory, 4 video, 3
multifunction, 3 misc., and 4 proto) in the series. Also, the table of
contents alludes to another assembly book for Apple clone boards.
Any info greatly appreciated.
Collector of classic computers
Lead engineer, Altair32 Emulator
Web site: <http://highgate.comm.sfu.ca/~rcini/classiccmp/>
Web site: http://www.altair32.com/
>Subject: Re: Vector Imagery
> From: "Ethan Dicks" <ethan.dicks at gmail.com>
> Date: Sun, 02 Jul 2006 18:49:18 +1200
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>On 7/2/06, Chuck Guzis <cclist at sydex.com> wrote:
>> > http://www.epanorama.net/circuits/dacs.html
>I've built that first simple ladder DAC (to hang a 1950s Triplett
>meter off of a parallel port for just random analog fun)... the
>problem is that it's difficult to tune the individual resistors to
>prevent the needle (or voltage) from going visibly *down* when
>transitioning the DAC from, say, 0x3F to 0x40 or 0x7F to 0x80. The
>cumulative errors of the low order bits can get to the point that you
>don't get a constant output increment by incrementing the digital
>value. The needle did deflect from 0 to full, but writing a ramping
>program showed very clearly that it wasn't a continuous progression.
First, the 1950s triplett meter is likely 20,000ohms/volt at will load
any ladder using resistors larger than 1000ohms in an R2R ladder.
The 5v range looks like a 100K resistor across the probes.
Second, The output port is TTL? CMOS? IF TTL the output swing is
not to 5V to with even light loads. IF CMOS output voltage will sag
if the load is too great.
For 8bit R2R ladders I use R=10k and 74HC244(or other high current
output CMOS) as a buffer. The load is usually very high impedence
(VTVM, FETVM, DVM, OPamp voltage follower).
>What I really would like to find is a formula for calculating R2R
>ladder values so that I could get a 0V-5V output from an 8-bit
>parallel port. Constructing it is easy, once one knows what resistors
> > The Petticoat 5 looks like it might have been built from the carcass of
> > an HP 9825 calculator/computer.
> Good spot! Now someone's going to get upset that it was maybe gutted to make
> a TV prop :)
actually it may be even worse, because the "petticoat" looks like the
even rarer 9835A (http://hpmuseum.net/image.php?file=992), which looks
very much like the 9825, but does not have the LED display or printer.
BTW although the monitor on top of the peticoat, looks like an HP
monitor (e.g. like the one used for the HP-86), the 9835A used a
totally different monitor.
Don't know if it'd work, but since you're ordering parts anyway
would a regulated charge pump work? I assume you're not using
the control lines; if you diode-or them together with maybe some
small resistors to limit & balance the load and set 'em high, they
oughta be good for 30-40ma, and if you're using a DAC it shouldn't
draw nearly as much power as an R-2R ladder...
It's often done with RS-232 gizmos, but I don't see why it wouldn't
work on the Parallel port as well.
Just a thought (and probably not a good one...)
Date: Tue, 4 Jul 2006 18:35:37 +1200
From: "Ethan Dicks" <ethan.dicks at gmail.com>
Subject: Powering (or not) a parallel-port-attached DAC (was Re:
On 7/4/06, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
> Obviously you might well not be able to do this. In which case, you
> either have to buffer the port lines (to reduce the output impedance
> there) or add a buffer amplifier on the analogue output. Either solution
> involves active components that need power.
I know that the "right" way to do it involves active components...
given my 95% success with passive components, I was hoping to squeak
by. If I could get power and data from the same source (see below), I
wouldn't be quite so picky.
> The Lorenz equation is remarkable for it's conciseness. I recall that
>when I first learned about it (late 80's?) I was told that it was
>originally intended to model some sort of atmospheric or gas flow
When I first heard of the Lorenz attractor, I read that Lorenz was trying to model
weather on a Royal-McBee computer (ontopic!), but due to processing constraints
was forced to drop everything but the wind (and perhaps temperature, but I'm not sure there)
The Lorenz Attractor came out of these equations.
Came out of a popular article, so, remember, "The Guide is definitive, reality is frequently inaccurate"