well hello everyone and welcome back to
adrianne's digital basement on today's
video we're going back in time in a
little bit to take a look at this
machine the Southwest technical products
6800 computer system got to make sure I
say the name right I recently had a
video on the second Channel where I
showed a really old potentially kit SL
homemade Slade by a company but a oneoff
computer that was given to me and if you
haven't seen that video it's kind of
interesting um I'm still trying to
figure out out what the details around
that computer are and actually by the
time you see this video I may already
know a little bit about that machine but
unlike that oneoff computer this machine
here is actually somewhat historical of
a computer but yet it's something I had
never personally ever heard of until
just the other day actually and then I
ended up with one of them so without
further Ado let's take a closer look at
this thing see if I can even get it
working
[Music]
I mentioned in the intro that I thought
this computer was historical and when
you think about computers that are known
in history to be significant or
groundbreaking in the realm of Home
Computing it all goes back to the
original alir
before the AL computers were pretty much
relegated to companies or universities
or governments and not really to the
home so when alter released that first
kit computer it really was quite
revolutionary but it wasn't long after
the alter came out that other kit
computers came out on the market for
home users from my understanding it was
only about 6 months later that the MSI
880 came out which was actually really
just an alair clone but this was another
machine that came out around 6 months
after the alair did so it was in later
1975 the Southwest technical Products
Corporation that's their logo right
there released this machine the 6800
computer system unlike the alter and the
MSI this actually uses the Motorola 6800
8bit
microprocessor the Motorola chip in this
very much like the intile chip was an
apit processor it supported 64k of RAM
and was relatively ground braking for
its capabilities but also its low cost
now there's one big obvious difference
between this computer and the MSI and
the alter of course is the front panel
is really pretty boring looking having
just a power button and a reset switch
here this clear part of the case here is
actually just that it doesn't actually
have any lights or anything behind it so
this is it for this computer now while
the blank front plate on this is a
little less sexy than the one on the
other machines this this computer
actually was a lot more functional in
that all of the control of the computer
was done through a Serial port on the
back which you would combine with a
terminal or a teletype so that you
didn't have to be flipping switches to
load programs you could actually
directly load programs off of paper tape
or even cassette with an adapter through
that serial Port later versions of
alter's computers and pretty much all
the other kit type computers that came
out after this also had the ROM based
monitor with the serial port and did
away with all those front panel
switches now this particular computer
was actually saved from going to East
and given to me and I think a lot of the
reason why it was almost sent to e-waist
is because it doesn't have that sex
appeal that those other machines have
nor the cache or like the notoriety so
that someone looking at this computer
might not realize what it is and just
toss it out now this particular example
is a little bit Rough and Ready in the
condition Department the front panel is
actually not that bad it's missing a
metal trim piece that goes around the
front and I'll show a picture of it here
how it should look I think that part's
gone because if you take the cover off
of this you have to remove that trim
piece first and there's one on the back
as well and then you can take the cover
off and if you're going in and out the
computer a lot it's probably annoying
and you just did away with it but
because of that missing cover there's a
little like dense and Nix in the corners
of the front plate here which would be
mostly hidden if if the trim was
actually there another interesting
aspect of this computer is that the top
cover is entirely made with this metal
grate here which allows really good
ventilation of the system meaning that
there is no fan installed in here which
is unlike the alter and MSI and of
course back then those fans would have
been Main's powered fans and quite noisy
so nice that this machine is dead silent
if you're using it at least with a CRT
based terminal as opposed to a teletype
which are very noisy on their own
flipping the computer around to the back
we have two db2s here one labeled
control one labeled nothing uh two extra
spots for db2s and then four holes that
you can run cables through I guess and
the power cable just sticks through the
back like that it's too prong it's not
even grounded but this was the old days
it's not like there was any kind of RF
shielding on this machine or any kind of
safety whatsoever actually and just like
the out this machine here was sold only
only as a kit so you could buy all the
parts to make this and you got the case
and all the circuit boards and the power
supply and whatnot but you still had to
put it together yourself it meant that
you included all the ic's the circuit
board stuff like that but you had to do
all the soldering yourself but one thing
about this machine compared to the alter
which was pretty significant besides the
visual difference and the ROM based
serial monitor stuff like that this
machine was really really inexpensive at
the time this computer came out it was
definitely a competitor to the alter and
was pretty comparable as well both were
kit computers and this ad which was from
May 1975 shows the alair price here
$439 for the kit with the assembly
instructions if we take a look at this
brochure from around October 1975 for
the 6800 computer system you can see
here that the complete kit was $450 us
which was actually slight slightly more
expensive than the kit form of the alter
but there's actually one big difference
if we look down here it says that the
basic Kit only includes the alter the
CPU and the front panel it didn't come
with anything else including Ram or any
IO cards to add 1K of ram cost you
$176 or 4K for
$264 when we take a look at what the
6800 included you can see here it
includes the MP a b c d FM and P well
let's break down what each of those
parts are so MPA is the microprocessor
system board so this included a little
bit of static Ram 128 bytes I think the
clocks the ROM to get the system booted
and the processor included the
motherboard which has the address
decoders it included MPC as well which
as you see here is a TTY current Loop or
rs232 terminal interface board that was
included with the kit that goes back to
what I was saying earlier is that unlike
the alair and the side there are no
controls in the front of the machine you
do all of the setup configuration and
execution using the machine language
monitor that's included on the ROM you
got the chassis cover with aluminum and
black finish but right here you got mpm
memory board with 2K of static memory
expandable to 4K with the MPX kit below
so for your
$450 you actually got the serial board
and the memory board with 2K that you
didn't get with the outar you could buy
an additional 2K of ram to go up to 4K
total for another
$45 so if we imagine here that you buy
this system and you want to upgrade it
to 4K of ram you're going to need the
$450 plus the $45 here so you're at $495
total for the kit meanwhile for the
alter you're spending
$439 Plus for 4K $264 more do for $693
and if you wanted to have a Serial Port
as well you need to add that board which
I'm not sure how much that cost but it
says they did offer it here just as a
reference I'm using the Consumer Price
Index inflation calculator the
$693 that the out cost with the 4K Ram
is the equivalent of
$3,700 in today's money compare that to
the $2,600 for the 6800 system there is
one other consideration on the altara
you could use the front panel to do
simple calculations or create little
programs that flashlights or do whatever
but ultimately wasn't super flexible
when it came to using the computer as
what we would consider a computer today
as I mentioned on the 6800 computer you
had to hook up something to the serial
Port that was on this interface this
control board right here and if you got
this computer without having any way to
hook it up to something like a teletype
or a Serial terminal you actually
weren't able to use the computer at all
Southwest technical Products Corporation
did actually sell a computer terminal
kit and it was $275 so definitely not
cheap at all and here is a picture of
that assembled kit which is actually an
iteration on the original TV typewriter
which was pretty much the very first
device in
1973 which let you hook a computer or at
least a keyboard up to a monitor and see
text displayed on it from my
understanding one of the big
improvements on this later version was
that you used static Ram as opposed to
shift registered which allowed you to
move the cursor around and edit any part
of the screen one other thing to
consider is that this kit did not
include any kind of monitor or CRT you
had to use your TV set or a security
camera monitor like seeing here now if
we add the price of the terminal kit to
the 6800 computer it was $770 which was
more than the alair with the 4K of ram
but remember for $693 for the AL you're
still getting a computer where you have
to interact with it through the front
panel and that's it meanwhile on the
6800 for $770 you got a computer that
actually had a keyboard and a monitor
while you hook it up up to a monitor and
then you can interact with it with a
keyboard which was much more how we
expect to use computers even today now
that we know a little bit about this
machine let's open this thing up take a
look inside now normally there are I
think 14 screws that hold the top cover
on and of course that trim piece is
installed on the front and back which
completes the look and also um makes it
a little bit less sharp along the edges
here I only have two screws installed in
here because when I got this computer it
didn't have any screws installed in it
whatsoever the machine itself was
actually in pretty rough shape it was
very dirty and there's definitely
evidence that this was stored in a let's
say less than ideal environment since
this machine has been in the basement
all I've done to it is clean it up a
little bit because it was really quite
dirty the power supply section here you
can see there's quite a bit of rust on
the Transformer and of course the fact
that the case is open on the top means
that any kind of moisture or dirt or
whatever can fall straight down into to
this so this is obviously rusted over
time it shouldn't cause a problem though
and if this computer ends up working
well I can take the power supply out or
take this Transformer out and give it a
little coating of rust converter and
then black spray paint the way this
power supply works is very common for
Machines of this era the mains comes in
it's reduced to a lower ac voltage
there's a bridge rectifier right here
that's mounted upside down onto the
chassis the output of that is DC and it
goes into this large filter capacitor
here which which then feeds to this
board which makes its way to the power
connector which is currently unplugged
it's right here and that's what goes to
the motherboard the large cap is
producing around roughly 8 volts on
regulated DC which when it gets to the
motherboard and these cards they have
voltage Regulators on them that bring it
down to the 5 volts and this little
board also has four diodes and two
capacitors on it along with this fuse
and this generates A+ 12 and a minus
12vt unregulated DC and that goes to the
motherboard as well through the power
connector right here that would almost
certainly be for serial lines or any
other chips that need like a+2 or a
minus5 and they would use voltage
Regulators on those boards locally to
actually generate those voltages you
might think these caps don't look quite
right and that's right the two that were
on here had bulged and were in really
bad shape so I actually replaced them
these are modern 1,000 microfarad nions
and I didn't have the axial type so I
just stuck these in here for now I
suppose if I want to try to restore this
to something that looks a little more
correct I guess I would use some axials
but to be honest this is totally fine
like this and this large cap here which
is made by mallerie actually unplugged
the leads here and used my bench power
supply and a very low amount of current
to actually reform this over a long
period of time so this cap is also
working perfect but I have not yet
connected power to the motherboard or
any of these cards because I wanted to
do that on camera just in case anything
goes catastrophically wrong now let's
talk about the slots here there are
seven slots in the front and they're 50
pins each these are for the CPU card and
all the main expansion cards that
essentially need all the address and
data bus lines all the signals that are
from the CPU and then on the back of the
motherboard there are seven more slots
that use a smaller 30 pin connector and
the reason for this is because there are
actually some ic's down on the
motherboard right there you see them
here and these actually do address
decoding and each of these slots is
addressable with 0 through 7even right
here so each one of them has a few bites
of address space Associated to them so
when you plug a card into this slot
right here it's just like on the Apple 2
where you can address that at a specific
memory location because of the address
decoding that's on the motherboard here
the S100 bus machines didn't have
anything like that and nor do say the
ISA bus on the PC doesn't matter where
you plug a card in it just works and you
have to map the io space or the iio
address space so you can address that
card properly it is my understanding
that the benefit of doing this address
decoding on the motherboard here allows
for much simpler cards here because
otherwise you'd have to be doing all the
address decoding on the card itself now
this right here is the serial console
card so this is what you would hook your
serial terminal up to when you Boo the
computer and you can see here that there
just is not a lot going on and that's
all because of the fact that the
motherboard is doing nty coding another
big difference between this motherboard
design and the alair S100 bus is look at
the connector it uses these sort of
Molex connectors and these very thick
pins on the motherboard and it's like
that for all of the slots it's a very
substantial connection and actually I
already took these cards off once to
sort of clean the motherboard a little
bit and it was really really hard to get
them off they were almost stuck on there
so let's go through the various cards on
this motherboard we'll start with the
one I have in my hand right here this is
the
MPC which is the control card I'm pretty
sure that stands for and it's connected
to the control port on the back of the
machine and it is serial so there's just
uh three wires here and this uses the
Motorola
6820 chip right here which is from my
understanding a parallel IO chip it is
not a Serial uart or anything like that
but a parallel one and the monitor ROM
that's on this machine actually bit
bangs seral over this parallel chip and
I learned this fact after binge watching
a bunch of videos on this computer on
this great YouTube channel which uh I'll
show a picture of it right here it's a
small Channel where the creator has
shown off many of the cool things about
this computer and I've learned quite a
bit so without his channel I I would
have been having to do a ton more
research reading documentation and
whatnot and what I learned is that the
monitor ROM that's included on this
thing it's on the CPU board which is
beyond the camera view right here that
was actually made by Motorola and it's a
mask ROM so it was already off the shelf
and the way that ROM addressed the
various components in the machine like
this bus over here and whatnot was
already predetermined and because this
card is a hard coded design for that
Motorola ROM it can only work at 300 bod
or 110 B and there are two jumpers right
here to configure that so when we do
test this thing out it's going to be
kind of slow the serial connection on
the top of the board uses that same type
of pin header Arrangement as on the
motherboard so I've unplugged that there
this card here is an mp- S another OEM
card from Southwest and as you see here
it has a b rate selector up to 1,200 and
I'm pretty sure this is MC 6850 chip is
actually a Serial chip it's not a
parallel chip that is bit banged but
that hard-coated ROM will only work with
that other one and we can't get 12200 B
for the terminal or like you know the
console out of this thing the next card
that's in here is the mp- LA which I'm
pretty sure is like a parallel IO card
so it's much like the user port on the
vic2 or the pet of commer 64 which
allows you in software to toggle IO pins
off and on right here so this would be
good for not just hooking up say
something like a printer or an LCD
screen or whatever externally but you
could hook up sensors or other external
peripherals to this thing and have it
all go through this MC
6821 which I'm pretty sure is a very
similar or compatible chip to the io
controllers that are on the pet for the
keyboard as an
example okay moving on to the large
cards here let's see if I can get these
out okay they're much easier to remove
now when I put them back in the machine
I use deoxit on the connectors which of
course has a lubricant in it which
allows you to get the cards in and out a
lot more easily first time I tried to
get the cards out I actually broke some
of the plastic standoffs that hold the
motherboard down uh because they're just
the little clip ones you push in and
push the motherboard onto they broke off
I just actually installed some metal
standoffs under the motherboard on this
side so now it's held in actually more
securely than it was even originally all
right the next board here is the mp- m
board which is another OEM card it's a
Ram Board now originally when you bought
this if you got the kit computer for
$395 you got this board and it came with
4K of ram here and one of these voltage
Regulators actually I think the kit
might have come with the expansion
memory as well so what they did is when
they sold it to you if you wanted to
save money you could opt for a 2K system
where you installed half the RAM and
then later you could buy the additional
RAM and the voltage regulator and put
that on and you'd end up with a 4K board
that's what we have going on here
unfortunately the markings on these
chips are all pretty much worn off they
seem to have like a plastic casing to
them these are static RAM chips and one
of the reasons why there aren't a whole
lot of chips on this Ram Board is it
doesn't need to worry about doing Dam
refresh so static Ram was a little bit
expensive back in the day but it
definitely simplified the overall design
of the whole computer looks like this
chip here actually has a marking that is
visible it looks like it's a 21
L2 from 1977 21st week and that's that
coincides with pretty much all the chips
that are in this machine it seems like
this was a slightly later machine in
that it was purchased in 1977 versus
like when it first came out in late
1975 when this machine came out
computers were advancing so incredibly
rapidly like what came out in 1975 this
machine was very quickly outdated by
machines that came out just a couple
years later and if you look at the Apple
2 that's a great example that in 1977
when Apple 2 came out it had graphics
and sound and a keyboard and everything
was all built in and expandability and a
switching power supply just a couple
years later even the grandfather of
these machines the aler was actually
discontinued from my understanding the
very first model at least in
1978 I'm not sure when this machine was
discontinued but I can't imagine that it
went much longer after this machine was
purchased there was a later version of
this machine I saw pictures of that seem
to use the Motorola 689 processor and
that was the same processor used in the
trs8 color computer but I have a feeling
that people who bought this invested in
this early model here were probably
using it for quite a while because it
was still a very functional machine back
to the hardware that's in this machine
here I'm just noticing right here
there's a little jumper link that has an
A and it's put into this little pin here
that says seven I wouldn't be surprised
if this jumper selects where in the
memory address space of the CPU this Ram
Board shows up this probably indicates
that this shows up at 7,000
hex all right let's try to get the next
board out of here oh yeah these are easy
to pull out with the deoxit that's
awesome all right so this board right
here this is the CPU board this also
came with the computer or the kit of
course it's the
mp- here's the Motorola 68000 right here
1977 day code 26 week over here on the
board we have two ic's this one right
here I'm pretty sure is that ROM ship
here it's the 6810 this is that monitor
ROM I talked about that was hardcoded to
address like the console port on that
specific serial card or parallel card
and right here we have an MC 6830
p8 quite sure this is static Ram I think
it's 128 bytes and the static Ram is
mapped into a fixed address space I
think at 8,000 hex which is directly
used by the monitor ROM for storing
registers stack information stuff like
that what's neat is even without that
other Ram Board installed or working in
the machine this static Ram if this
works should be enough to get this
machine up and booted where I can at
least type in commands and read and
write to this memory in that little tiny
address space there all right moving on
there are two more boards in here let's
pull out this front one here oh it's
really really stuck in there very firmly
there we go it came out all right so
this is a Ram Board and this one is not
made by Southwest and if you you'll
notice right here this is made by smoke
signal broadcasting it looks like it has
a serial number of
2877 and on the front side of the board
here it says SSB for smoke signal
broadcasting
m16a so that would be a 16 kilobyte Ram
Board and notice here there's a couple
chips in socket so I guess uh they have
gone bad and at some point in the past
someone has replaced them these are TMS
444s from Texas Instruments I think
these chips are 4K by 1 bit chips so you
would need eight of these to equal 4K
total of 8 bit memory meaning this of
course this board has 16k on it I
definitely don't have any Ram that is
like this so I don't think it'd be too
hard to take a 16k stattic ram chip for
instance and just wire that directly in
to like this select logic right here in
the address data bus lines and kind of
replace all of these with just one IC as
I mentioned that this power supply on
this board is unregulated each Board
needs its own voltage regulator and this
one obviously has a larger one because
there's more ic's on here so they're
using a bigger uh 5vt regulator with
this heat sink here in addition there's
dip switches here which almost certainly
is for selecting where in memory this
stuff is mapped into and I wouldn't be
surprised if this board is configured
right now into address space 0000 at the
beginning of ram I'm noticing here
there's a little bit of damage caused by
those two sockets when they were
installed Sol a few traces were lifted
so if there's a problem on this boort I
can always double check to make sure
that uh this is not more of a problem
without things like the hako and
desoldering iron and other hot air
stations it would have been hard to get
these chips out of this board all right
we're down to the last card that's in
this machine pop this one out this is a
floppy Drive controller it's got the FD
1771 B which I'm pretty sure is the
exact same chip that is used in the trcd
model 2 that I was working on I was
thinking that this chip here is probably
a ROM chip cuz I mean there needs to be
a ROM on this board this is a
74s 474 n I'm going to have to go look
up what that is exactly and then this
right here is the Motorola
6821 so that's like a parallel IO
controller chip which is used for what
it's to control the floppy controller it
looks like so instead of hooking the
floppy controller directly up to the bus
they're driving it through this uh
parallel IO chip that's interesting this
board here is from 1977 smoke signal
broadcasting as well and does it have a
part number on the top I don't see it
just says Hank white number
13104 is that who put it together or
that the owner of this machine oh it
does say right here BFD 68
I know at the time this controller came
out there were other controllers that
came out for this machine right around
that same time period like the one made
by Southwest Techo products actually
connected to one of these IO connectors
on the back here and there was a
replacement ROM that went on the CPU
card that replaced that Motorola one
that had commands that would directly
address the uh floppy Controller made by
them so you could like boot directly off
a disc really easily but there were
other cars that plugged onto these slots
in the front that had ROM chips right on
them that contain the Doss or the disc
oper system for the drive so you didn't
even need to take up any space on your
floppy disc to use the drives you just
executed what was in the ROMs here from
the machine language monitor you just
issued one command and then you were up
and running with disc drives hopefully
this thing works in a similar way and if
not then hopefully I can find the manual
to try to figure out how this thing
works a quick Google search does reveal
that the 74s 474 that is on this board
right here is indeed a 4 kilobit prom
I'm pretty sure that's 4 kilobit yep 512
bytes by 8 Bits bipolar prom that means
that you could just execute code
straight out of this and it's only 512
bytes in size which isn't a whole lot
but I wouldn't be surprised if this is
mapped to the
c0000 address space so you can just go
right to it to start booting your floppy
discs I spent some time Googling for the
manual for this particular disc
controller card but I actually couldn't
find it I did find this advertisement
for it it looks like it came with this
external drive chassis it does mention
here it has a built-in ROM for booting
right off your floppy disc but the
problem is it seems to indicate there
are two different versions of Doss one
that loads into 7,000 hex and one that
loads into d000 hex I searched around
for dis images of them and I found one
actually on archive.org but it's the
version that loads into d000 and now
we've looked at the ram boards that come
with this machine there is no memory on
this machine up in that higher range
where this dos dis wants to load so if
anyone can find a scan of the original
manual and also an image of that dos dis
that loads into 7,000 that'd be really
helpful and that completes the tour of
the Southwest technical Products
Corporation 68,000 computer system what
a mouthful that is in the next video
I'll be diving into this machine to see
if I can get it actually up and running
after all these years who knows last
time this thing was even powered up let
alone worked I hope you enjoyed this
introduction to this computer I've been
finding this absolutely fascinating I
know very little about this 7s era of
machines at least before the pet and the
Apple 2 and the tr80 came out this sort
of home brew kit stuff is quite unknown
to me and I find it so fascinating how
it was like such a an open Community
people were hacking and modifying the
hardware and companies were cloning each
other and making all sorts of
interesting machines after doing some
research I found that this particular
machine was the basis of a whole bunch
of other computers that were 6800 and
6809 based even that smoke signal
broadcasting company that made the ram
card and the disc drive in here actually
made a version of one of these computers
with the same bus connectors as this
called ss50 and ss30 and then it had
built-in disc drives as well it's really
fascinating to me that this was an
alternative to the S100 bus which I
thought pretty much took over the entire
world when it came to home computers at
least until personal computers came out
like the IBM PC and the commer 64 and of
course other stuff like that which this
completely obliterated anyone wanting to
use these types of machines and that of
course happened in the 80s so anyhow if
you like this video thumbs up if you
didn't you know what to do hit that
subscribe button you all the good stuff
huge thanks to my patrons their names
are SC up the side of the screen if you
want to become a patron you can do so at
the link in the description below and of
course a huge thanks to the local viewer
here in town who donated this computer
to me and actually saved it from being
ewed so thank you very much for that
it's been a fascinating journey and I
know there's going to be more
interesting videos around this machine
if you want to know more about this
machine don't forget to check out the
YouTube channel that I showed earlier
I'll be putting a link in the
description to that there's cool info
there about both this machine and the
alt so that's going to be it stay
healthy stay safe and I will see you
next time bye
[Music]