In the past few months, I've been heavily involved with upgrading
some CAT scanners that date from the late 70's. I've mostly been involved
with the PDP-11 side, but bolted onto the PDP-11 (or, actually, the other
way around) there's a custom piece of hardware (two dozen hex-height
cards) that does all the heavy number crunching. Backprojection is
what the process is called, and it's basically a deconvolution of the
data measured by the individual detectors to make the pretty picture
of your insides that a CAT scanner displays.
The power and speed of this classic hardware is quite impressive,
considering it's nearly 20 years old now. We've been timing other
approaches to backprojection, and if we implement the same algorithm
that the custom hardware is doing but on a modern 533 MHz Pentium III,
we discover that the custom hardware is twice as fast as the Pentium.
There are some other competing technologies, making use of DSP chips,
which promise to be faster, but at a substantial development cost.
Is this a fair comparison? Maybe not! The Pentium system costs roughly
$2000, while the custom backprojection hardware was several hundred
thousand dollars back in the late 70's.
The PC boards that make up the backprojector make use of a unique
technology: the PC boards themselves are just plain old two-layer boards,
with the actual PC traces carrying only power and ground. All the actual
wiring is done by fine machine-laid wiring between pads, with all
the wire layers "potted" in a plastic compound. Obviously, reworking
such a PC board is extremely difficult, but it gives impressive component
densities for the time. The modern equivalent of this is multi-layer
PC boards, naturally.
Of course, there's another sort of power involved too: the custom
backprojection hardware requires +5V at 350 Amps, and some installations
have multiple backprojectors!
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
<> I have em. Both 10 sector NS* format (no even for $20 I dont give them
<> up) and also some of my TI99/4a likely others that I'd have bought aroun
<
<Wow! What brand of diskettes were they? All the NS diskettes I've seen
<have the standard windows, but I think they were just 3M and Verbatim
<diskettes.
Actually a mix of NS* hard sector and some soft sector, Shugart, dysan,
Verbatum, memorex and 3M, looking at them. It's a standards thing. At
the time 1978 35 track was the standard, 40 wasn't far behind but it was
different in that the media had to have a longer opening to work right.
Allison
<This was known by the trademark "Multiwire", and was often used for
<quick-turn production. DEC used it on a few boards in the KL10-PV
<processor; later revisions of the same boards were conventional PCBs.
that was it. It's had two characteristics, high density and lines could
cross (it was insulated). Since the "inner layers" were power and ground
they were easy to modify (wires could be seen and removed or cut) and the
transmission line characteristics were better than the then vogue 2 layer
boards. All the lead holes were plated through as were any vias.
Allison
I grabbed a copy of the picture... a little dark... I had to do some
adjustments to it...
What I see are:
o Two H960 tall cabs
o One cab has 4 RL series drives in it (pretty obvious)
o The other has what appears to be a pdp-8/e/f and two
pdp-8/A's, both with the programmer console.
Megan Gentry
Former RT-11 Developer
+--------------------------------+-------------------------------------+
| Megan Gentry, EMT/B, PP-ASEL | Internet (work): gentry!zk3.dec.com |
| Unix Support Engineering Group | (home): mbg!world.std.com |
| Compaq Computer Corporation | addresses need '@' in place of '!' |
| 110 Spitbrook Rd. ZK03-2/T43 | URL: http://world.std.com/~mbg/ |
| Nashua, NH 03062 | "pdp-11 programmer - some assembler |
| (603) 884 1055 | required." - mbg |
+--------------------------------+-------------------------------------+
--- allisonp(a)world.std.com wrote:
> > The fact that the machine hangs solid when the card is where it's
> > supposed to be may be a clue that the it's permanently stuck interrupting.
>
> Depending on backplane the grant may not end-up where you guess it is.
I was assuming a sinusoidal AB-AB chain starting from the slots labelled
"A" and "B" (out of A, B, C, and D). Now... the one twist is that the cards
are installed with the CPU facing the bottom of the cage (solder side up),
but the keys on the backplane connectors are a dead giveaway.
> My memory is fuzzy on this but I think Ht-11 (heath os) did not like RTC
> <line event> interrupt and would hang on that.
Hmm... I don't have any HT-11 disks, only RT-11. But the LTC *was* enabled.
> Yes, also DLV11 or the heath serial card both should have HALT on BREAK
> enabled. <both support it as do the 11/03>
I didn't even try that. For now, because of bootstrap considerations, I'm
running with an 11/23plus CPU and a VT-220 (because it's close).
Speaking of bootstraps, what did the H-11 come with stock? BDV-11? Custom
Heath board?
-ethan
=====
Infinet has been sold. The domain is going away in February.
Please send all replies to
erd(a)iname.com
__________________________________________________
Do You Yahoo!?
Bid and sell for free at http://auctions.yahoo.com
>Yes it was or in a later time frame m8186 (kdf11, 11/23) with m8044s.
>that workes better than 11/23+ (m8189) as it was a dual solution and the
>hath backplane was rather cramped.
Mine actually has an 11/53+ board in it... :-) I do have the H27 board
and drives and a heath serial line board, though I use a DLV11-J and
and -E in it. I also have an RQDX3 connected to a table-top RD54
nowadays...
Megan Gentry
Former RT-11 Developer
+--------------------------------+-------------------------------------+
| Megan Gentry, EMT/B, PP-ASEL | Internet (work): gentry!zk3.dec.com |
| Unix Support Engineering Group | (home): mbg!world.std.com |
| Compaq Computer Corporation | addresses need '@' in place of '!' |
| 110 Spitbrook Rd. ZK03-2/T43 | URL: http://world.std.com/~mbg/ |
| Nashua, NH 03062 | "pdp-11 programmer - some assembler |
| (603) 884 1055 | required." - mbg |
+--------------------------------+-------------------------------------+
>By the way, I am curious where you got your lander program... I ask
>because a few years back, I contacted Jack (via a pointer from the
>Computer Museum in Boston), and what he had was a 9 -Track tape that he
>had gotten from someone who had preserved a copy while he was at the
>University of Wisconsin-Milwaukee. He sent me the tape, and I read it
>and returned the contents to him, including the lander program, some demo
>programs, etc.
The version I have is the one I obtained back in 1975 or so... one
that Jack and I worked on when I was a student at WPI and he was
visiting the college for some reason... The ME department had a
GT44 (11/40 based system with a VT11 and VR14) and we did some work
on it to fix some intensity problems with the thrust and directional
control bars as well as getting it to work with a programmable clock.
Megan Gentry
Former RT-11 Developer
+--------------------------------+-------------------------------------+
| Megan Gentry, EMT/B, PP-ASEL | Internet (work): gentry!zk3.dec.com |
| Unix Support Engineering Group | (home): mbg!world.std.com |
| Compaq Computer Corporation | addresses need '@' in place of '!' |
| 110 Spitbrook Rd. ZK03-2/T43 | URL: http://world.std.com/~mbg/ |
| Nashua, NH 03062 | "pdp-11 programmer - some assembler |
| (603) 884 1055 | required." - mbg |
+--------------------------------+-------------------------------------+
I will be in Philadelphia all day Friday with nothing but time on my hands.
Can anyone recommend any good hunting grounds for 1975 - 1985 micro's or
micro magazines?
Bob Stek
bobstek(a)ix.netcom.com
Saver of Lost SOLs
The above may be of some interest to list subscribers in Australia:
------------------------------------
The School of Psychology has some old computer gear which is of no
commercial value. The items include:
Apple II with various interface cards, MicronEye video camera, printer
Commodore Amiga computers and accessories
Commodore Vic 20 Computers and accessories
These items may or may not be in working order, but may be of
interest to someone who collects ancient computers. I'd hate to have to
throw them in the big green bin.
If interested please contact me, or one of the Psychology Technical
staff.
--
Dave Heap mailto:dheap@metz.une.edu.au
School of Psychology, <= postal address
University of New England, phone: + 61 2 6773 2587 fax: + 61 2 6773 3820
Armidale NSW 2351, Australia http://metz.une.edu.au/~dheap/
