The one thing you could do with a real front panel (not the debugger ROMs
and a keyboard/LED display) is debug new card designs. Remember the Morrow
S-100 extender card with the built-in logic probe? For those of us who
wanted to build our own cards (remember wirewrap too?) but couldn't afford a
home o-scope, much less a logic analyzer, the logic probe and single
stepping front panel were invaluable. You could actually single step
execute an I/O command and see the address and data bus decode on the
peripheral card. And when you finished soldering that new 8KB static RAM
board full of 2102s, you could see the bit change from 1 to 0 right before
your eyes, no better way to find a bad chip or solder joint.
The best thing IMSAI ever did was come out with a good front panel, not that
wiring nightmare that MITS put on the Altair. I still have a running IMSAI
with the front panel (circa 1977), plus an Ithaca Intersystems S-100 with
the front panel, which was only a slight improvement over the IMSAI version.
I also had one homebrew S-100 with the Wameco front panel, which used hex
displays for address and data but otherwise was identical to the IMSAI front
panel. Does anyone remember other front panel S-100 cards besides MITS,
IMSAI, Ithaca, and Wameco? Wasn't there a Byte-8 sold by Olson Electronics
for a while that also had a front panel?
Well actually the Vector 4 (accoding to the doc) has both a Z80B and a
8088-2, they can be individually selected through the use of port 0cH and
port 0dH. They are both clocked at 5.1 MHz.
And yes the Floppies are hard sectored (16) for a total capacity of 630 KB.
They can also be eqiped with a 5MB HD
-------------------------------------------------------------
Fran?ois
Visit the Sanctuary at: http://home.att.net/~francois.auradon
>Yes it was. One of my s100 boxen is a Vector MX (s100 crate only none of
>the original boards). The MX was z80 powered byt the Vector 4 may
>have been 8088(cpm-86 V1).
>
>Allison
>
A friend of mine was recently in D.C. and took this
photo of the Microcomputer exhibit in the Smithsonian
Museum. I recognize the Altair and the Sol but what
is the Apple prototype sitting on the table? Here is the
link to the photo...
http://home.att.net/~rwood54741/Museum50.jpg
Bob Wood
______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com
<I did some software work on a Horizon many years ago. As I recall, it ha
<two full height 5.25" bays, a good sized power supply behind the bays (o
<the right side) and a shorty S-100 card cage on the left, 8 card slots?
<the NS motherboard also had some logic on the motherboard, at the rear.
<believe there were one or two 8251 serial ports, a baud rate generator,
<maybe a parallel port or interrupt controller (look for an Intel 8214 or
<28-pin AMD IC)?
Err no. The back plane will have two 8251 serial port and a parallel port
and supporting ttl for same. It has a heartbeat timer for that can drive
interrupts. The interrupt logic is on the CPU ZPB-A and it allows 1-of-8
RST locations to be used (z80 mode 0). there isn't a 8214 in the whole
thing if it's a Horizon unless the board with it is not from NS*!
BTW, 112 slots though a full 64k system could be configured in as few as
three cards! The lineup would be CPU, 64k ram card, disk controller and
the IO already built into the mother board(2 serial and 1 parallel).
The power supply is responsable for 30% of the total weight and is
electrically robust.
It was easy to check, mine is sitting here cranking a z80 asm file.
Allison
< I think it uses the S-100 bus. According to their manual, North Star
<used the same disk controller in the Horizon that they sold for the S-10
<systems. I have a NS S-100 controller. They are the same electricaly and
<software wise but maybe physically different.
They are the same or close cousins and both S100. NS* prior to advantage
was nothing but an S100 house.
The first one sold (still have mine) was MDC-A a single density unit that
cound address up to three single sided drives.
The later MDS-A was a Double density controller for up to four twosided
drives.
Both were S100, the same form factor and had on board boot proms
nominally at the same standard address. The latter DD version would
read and write SD media as well.
Now as to formats and non NS* controllers. NONE of the FDC chips can
read the NS* format but a controller that could is easily built for most
any bus or cpu capable of reading data at the required rate and doing
the housework inbetween.
Allison
<These I/O ports are all 8 bit, right?
<
<Now, an S100 frontpanel would have 16 toggle switches (at least - to
<load a memory address). So why can't you either
You could they didn't and they board was chockfull of crap and a little
more would have made a mess of it.
In 1974 the altair was an "ok" design at best. It was one set of
engineers vision and at that point their best shot. They did it that
way.
Allison
<Was the latter really considered a problem in those days? Or was it
<just that as a result it wasn't real useful to have the front panel do
<that? (Or was it just the additional cost of having the front panel
<do that?)
Fancy way is, cost benefit ratio. It cost a lot! Another was, it's easier
to not do that. Actually it was rare I needed the ability.
Allison
<But what does an instruction do? It just generates bus cycles, right?
<The bus doesn't care whether those cycles come from the CPU or something
<else (unless there's bus mastering and arbitration, which I doubt).
In theory your correct.
<The difference between generating a memory cycle and and I/O cycle on an
<Intel CPU is simply a matter of clocking a different value onto the
<"control bus" (which might be a multiplexed bus, I don't know the 8080
<that well).
Reducing that to practice and at a low cost on S100 bus with an 8080 is a
different matter. To understand that you need to know both as S100 was
not a bidirectional data bus(seperate data in and data out paths) and
all the bus control signals were RAW 8080 status/controls making it a
royal pain to do DMA on the bus. To make a point to do a memory write
on the bus you have to output SWO/, PWR/, MWRITE, SMEMR, SOUT, SINP,
PDBIN and all of them must be in the correct state (some are active
high!). S100 was a poorly designed bus in that respect. I may add that
Altair 8800(a) and Imsai were not bus masters, they were more CPU control.
The best way to descrive this is if the CPU was Not there the front panel
was an ornament.
Allison
At 06:34 PM 2/24/98 PST, you wrote:
>A friend of mine was recently in D.C. and took this
>photo of the Microcomputer exhibit in the Smithsonian
>Museum. I recognize the Altair and the Sol but what
>is the Apple prototype sitting on the table? Here is the
>link to the photo...
Looks like an Apple I to me, but then again I've never seen an actual model
in person.
Hi, I just got back from a hamfest. Found two brand new in the box full
height Tandon floppy drives for the IBM PC. Rich, do you want one?
I also bought two AT&T 3B1 computers without keyboards or monitors. Does
anyone know if the keyboard and monitor from a AT&T 6300 will work on them?
Or where I can find a monitor and keyboard? Also need any advice about
how to get these up and running. What are all the ports for? etc
Joe
