As an unexpected freebie while I was picking up another pdp8 I've acquired a
small pdp11/15. I'm really an 8-man so this is a bit of a foreigner but it
seemed a shame to let it be thrown away.
It seems to be a fairly small system in a single box but beautifully clean
for a change ;o). The configuration sheet shows KC11, KF11-A, DL11, KG11-A,
MM11-F, MM11-f, DD11-A and H720F which seems to reflect the contents OK.
I've started browsing around but I'd welcome anyone giving me a rundown on
what these modules build up to.
I was quite interested to see the construction method with the cards
upside-down in the backplane and a snazzy rotatable rack mount for servicing
- unusual (to me at least).
Bob
Hi folks,
My aunt just emailed me to let me know she's got a friend with some
old floppies that she needs to get files off of.
They're Amsoft CF2 3" floppies, unfortunately something I've never had
in my collection, so I can't really help. If anyone on the list has
easy access to an Amstrad or ZX Spectrum system with a CF2 drive and
would be willing to help (possibly for a fee, I have no idea
whether/what they'd be willing to pay), please contact me off list,
and I'll try to get you connected!
Thanks,
-Seth
Mike asks:
> My real question is - 9 faulty out of 48, spread across both machines,
> seems very high. Are 4116s that unreliable? Or perhaps they're quite
> sensitive to power supply problems?
It isn't unusual to find that many years after manufacture, that a
particular batch of DRAM chips aren't reliable anymore.
DEC and other memory board makers used to keep internal lists
of known good batches and known bad batches of chips, and even
kept track of what brand/batch are shipped with each memory board
for long-term reliability tracking.
But it seems more likely that something marginal in the timing of the
motherboards or the power supply or something else is causing your
observed flakiness.
I don't really understand what you mean about the Apple II's "wouldn't
boot", though. They do not do an extensive (or any!) power-on memory test
but maybe loading DOS 3.3 is hitting RAM hard enough at power on
that it's turning somethng else up. As others have noted, just going
into BASIC at power-up doesn't hit memory too hard, and the quickie
tests of going into hi-res graphics and looking for flakiness on the screen
is useful if not definitive.
Tim.
Hi,
I just try to get a VT05 working with my PDP-8/e.
Having a tuned KL8E interface at 2400 baud.
I need fill characters....
Found a KL8E.PA in the OS/8 V3D sources. It is a two page handler and works.
But how do I get my system to use it as terminal handler? Or is there another one?
Best wishes,
Philipp :-)
--
http://www.hachti.de
First sorry for the delayed response.
Back when the Apple ][ Europlus were being sold new, and when
Microspot was actively selling them, one of my favourite ways of
finding RAM problems, was to type HGR2<return> and watch the screen.
It switched to displaying a large chunk of the second 16k bank as pure
raster graphics and then sets it all to black (zero). It only displays
seven bits of each byte on a mono monitor but any dead chips in those
seven shows up as recurring white (or randomly flashing) vertical
lines. If there is a fault in the first bank then the machine probably
will not start up, but if it does, typing HGR<return> displays the
first bank similarly but with four(?) lines of text at the bottom.
You can switch the RAM around to test bank 3 and the eighth bit of
each byte. By using the Basic commands (moveto and lineto?) you can
find out which bit has failed, or by switching RAM chips.
On 26 Apr 2009, at 18:00, cctalk-request at classiccmp.org wrote:
>
> Message: 3
> Date: Sun, 26 Apr 2009 23:38:28 +1200
> From: Mike van Bokhoven <mike at fenz.net>
> Subject: More broken Apples...
> To: General Discussion: On-Topic and Off-Topic Posts
> <cctalk at classiccmp.org>
> Message-ID: <49F447B4.1000708 at fenz.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Well, I dragged those Apple IIs out of storage, and spent this evening
> poking at them, with some success. Thought I'd post my results here,
> and
> hope that someone has some suggestions for me.
>
> There are three machines in total; one an Apple II Europlus, the other
> two generic II+ clones.
>
> The first thing I did was run them up - all dead, garbage on the
> screen.
> Same as last time I looked at them. Step 2 - pull all the cards and
> try
> again. After that, one of the clones ran up fine; turns out that the
> 'language card' (16k memory expansion) was killing it. Good stuff -
> one
> running Apple II, even if it's not an original.
>
> Unfortunately, the other two weren't quite so cooperative. I decided
> to
> look at the other clone first, as its behaviour was pretty
> interesting.
> The screen was entirely full of apostrophes to begin with, but
> randomly,
> blocks of them would change to lower case 'p's, and back, flickering
> very quickly. It responded to a reset by changing the pattern of ps,
> though they tended to appear in the same place. I found the ASCII
> values
> interesting:
>
> ' = 0x60 = 0110 0000
> p = 0x70 = 0111 0000
>
> So, on reset, perhaps it's clearing half the bits per byte, and the
> other four have a problem. Reseting the machine tended to lead to
> random
> behaviour for a bit, such as random display changes, and speaker
> clicks.
> At one point, the display switched to high-res mode, and I could see
> that a large amount of memory had the same sort of pattern through it,
> and was flickering the same way text was; I guess the entire memory
> space is like that. Perhaps bits 5 and 6 are permanently stuck.
>
> I checked the CPU's behaviour; on reset, the address and data lines
> would run for at least a short time, so I'm guessing the CPU is likely
> to be OK. Often they would continue to run, at which time I'd see the
> flickering. Other times, activity would stop, and the flickering would
> also stop, usually leaving a screen full of 's.
>
> So, my next step is to track down a schematic for the machine, and see
> what I can figure out. I'm guessing I should look first at anything
> that
> deals with the high four bits of memory. Thoughts, suggestions and
> intuitive guesses welcome!
On Wed, 29 Apr 2009 15:33:43 -0600, Richard <legalize at xmission.com>
wrote:
> Reasonable idea. I've seen surplus environment controlled trailers
> for sale on govliquidation.
This is a great way of going if you are willing to re-rack your
equipment. The electronics trailers are specially designed to channel
cooling to the racks - some having zone controls. Generally, there is
also sufficient power distribution to handle the equipment you
described.
A number of years ago I outfitted a thirty-foot surplus equipment
trailer with a Modcomp II, data recorders, printer, and data
acquisition equipment for an atmospheric optical transfer function
experiment. The trailer I came up with had a row of racks that
covered one side leaving the other for a console and printer and room
for everyone involved to escape the elements. We operated out of
Tucson, Arizona with sites at Cape Canaveral in the summer, Lake Tahoe
in the winter, and Bolder, Colorado in the summer. About 10,000 miles
of travel in all with no equipment failures!
There were two zones of cooling: one for the equipment in the bays and
the other for the personnel space. There was over 100 Amps available
in the racks with 3-phase 220/110V wiring.
Another avenue to investigate are surplus equipment shelters. These
shelters have environmental systems, racks, and power distribution.
You hire a crane/big fork lift and a flatbed to move the beasts and
generally will go for less than the trailers.
CRC
>
>Subject: Re: Transistors...
> From: Fred Cisin <cisin at xenosoft.com>
> Date: Wed, 29 Apr 2009 11:50:48 -0700 (PDT)
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On Tue, 28 Apr 2009, Allison wrote:
>> Common base transistor has current gain of .99999.. and voltage gain >1 as
>> well as power gain. Wire is .9999999.. for all those.
>
>Is common wire really THAT close (.9999999..) to 1.0?
>I always assumed that wire losses were more than that.
>Or does that require superconductors?
Not quite but compared to many other things unless second order effects
are important it's practical to use 1. Mostly as what you put in is
what out get out for small systems at low curents and moderatly low
frequencies. At grid tranmission line currents and distances even
that .000001 part is significant.
At RF, noticable at VHF and higher then the resistivity of the surface
is more important than bulk due to skin effect.
Thats a whole nother can of worms.
Allison
On Apr 29, 2009, at 20:29, Joost van Baal wrote:
> The machine will be rescued by the Centre for Computing History
> (www.computinghistory.org.uk) near Cambridge, UK. (It might even
> get hooked up
> on the internet, within a couple of months.) Thanks locutus for
> help in
> mediating. See http://abramowitz.uvt.nl/sgi.txt for latest status.
Joost asked me to communicate this to all of you, so here it is.
.tsooJ
