> No, I'm afraid you may have hit it on the head, and it's been the
> direction I've been leaning, that the microcode ROMs may have
> fried, but that just blows my mind. Tonight, I'll set up the
> PC that's got my ROM burner/reader, and read each one (if the
> ROMs aren't too large a size for my Needham unit). I'm assuming
> I'll see all 00s or all FFs (or maybe something like FEs) if
> they're blown; been a long time since I've looked at popped
> ROMs...
Ok, my microcode ROMs are fine, via direct observation
(dumped them to disk then ran them through my LOW7 filter
to strip the mark parity bit from the Prime ASCII. I also
verified the ROMs are OK by managing to provoke the system
to issue an error message that resides *only* in those ROMs.
> About the only other possibility is that the backplane got
> cooked, but it looks fine...
There are still some possibilities other than this, the
Primes appear to have been way-overengineered w/r/t making
sure the power is OK.
Thanks for all the suggestions, folks...
-dq
Hi,
I do cookies. It was something I did years ago{30+} to understand
all that stuff.
Allison
-----Original Message-----
From: John Allain <allain(a)panix.com>
To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org>
Date: Sunday, December 16, 2001 11:33 PM
Subject: Re: [PDP8-Lovers] how to clean a PDP8/A, dishwasher?
>> {everything about cores} -- Allison
>
>Thank-You very much for this. What's your consulting rate?
>
>> thats about it.
>
>No doubt.
>
>John A.
>
>
>
> Jim Arnott wrote:
> >
> > And what's the difference between an engineering project and Christmas?
> >
> > None. You do all the work and the fat guy in the suit gets all the credit.
> >
> > (did I read that here?)
> >
> > Jim
>
> And pay too!
Well, The Jolly Old Elf has to deal with some less-than-pleasant
happening.... the local radio stations have a Christmas song in
rotation titled "I Farted on Santa's Lap"... we should be so
lucky that the fat cats in suits would have one land on them...
-dq
> In practice the solution is to accept the fact that specs, no matter
> how much they are labored over, are for most efforts soft, and
> then describe mechanism to deal with uncertainty as part of the
> development process. Rapid prototype, stepwise refinement,
> the understanding that one cannot test their way to correctness and
> a willingness to throw at least one implementation completely
> away, coupled with small, agile teams that work with an active
> user community empirically produce more correct results in less
> time that alternative techniques.
This all sounds very familiar...
> Not like any of this is new. Brooks described this eons ago
> in _The Mythical Man Month_...
Ah, now I know why... insert <EWOK_WORSHIP_SOUND_EMOTICON> here.
I can't tell you how many managers I've wanted to strangle
using the prototype code they demanded I push into production...
-dq
> From: Ben Franchuk <bfranchuk(a)jetnet.ab.ca>
> "Should HTML/inline files be banded from EMAIL?" I ask.
> As of late I have turned inline viewing off, with all the
> stupid viruses around.
My vote: ban 'em.
Glen
0/0
> From: SUPRDAVE(a)aol.com
> >>Gee, a message from an AOL user with no HTML . . . imagine that . . .
> harrumph, will wonders ever fuckin cease?
Well, gee, no offense, it's just that html messages are a PITA to read with
my reader, and most lists and newsgroups frown on HTML posts.
> >> Kwanzaa is NOT a real holiday.
>
> >Okay, I'll bite: why isn't it?
>
> figure it out yourself, google is around for a reason
Google certainly is here for a reason, and I can do a search anytime I
like. My reason for asking is that you had stated an opinion, and I was
curious to find out more about your stated opinion. Based on the hostility
of your reply, I'll assume I was mistaken in asking.
Sheesh, man, what are you so pissed off about? This is a friendly list.
If you are so afraid of expressing your opinions, may I respectfully
suggest that you confine them to alt.flame.niggers, where you will find a
lot of other cowards to associate with.
FYI, I think it's a "made up" holiday and just wanted to know what your
thoughts were.
Glen
0/0
>does it have a spell-checker?
ROFL... well, I assume it does... and so does the email client I use... I
just never use the spell checker... sorry, dyslexia has completely
destroyed my ability to spell a damn thing, and I (as well as most
everyone I write to) have accepted this fact, so I just don't use spell
check as often as I really should. Heck... consider yourself lucky, I
only made 3 errors in the last email (Strictly and default x2)
But just for you... I spel chekt this emial :-)
-chris
<http://www.mythtech.net>
It takes quite a bit to read one bit (the same amount to read
all the bits on one sense line).
You need to in order:
Select the specific word (or bit) and drive it with the X and
Y lines, each will be 50% plus a tiny bit extra current
needed to switch a bit. And yes that is a regulated
current or wire melting may occur! Typically it's a pulse
of several hundred milliamps.
Then at the right time after the select pulse is applied
you will see a big or smaller pulse on the sense line.
the difference between a 1 or 0(zero) is the timing and
the height of that pulse.
That was the nasty item as both timing of the XY select
pulse and the time to the read window are current,
temperature and specific to the cores used. The resulting
signal is quite small and is measured in tens of millivolts
for a core that switched and maybe a millivolt for one that
did not. Yes, the sense line does have a lot of noise!
To do that again or write a 1/0 you need to reverse or
leave the XYselect polarity. The inhibit line (for a 4 wire
core mat ) can be the sense line for write (three wire mat).
To write the opposite data you select the core via XY with
enough current to flip the core, to not write that value you
apply enough current of the reversed polarity to the inhibit
line to reduce the field(from the XY selects) in the selected
core to less than the half select value.
The basic operation of reading implicity sets all cores in the word
line to the same state. To write (a word) along a word line you
reverse the currents and also apply inhibit current on a bit by
bit basis. The end result is some cores in the word flip (reverse
the magnetic field) and those inhibited do not.
Now... if you want simpler try this...
Wind about 20 turns of wire on a nail (iron, or better yet steel).
Wind another 20 turns. We use a lot of wire to get a BIG signal.
Now if you hook a simple 1-3V DC meter to one winding and
then hook the other winding to say a 1.5V battery you should
see the meter pulse (basic transformer action). If you interupt
the connection (off on off) you will see another pulse of differing
polarity (needle will go the other way for a moment). Do that a
few times to note the reaction and then reverse the battery and
repeat. When you do that you will not the meter action indicates
a bigger pulse the first time and back to like before if you do it
again. Now the majik of core. When you magnitize something
like that the nail/washer/core takes a magnetic polarity and
holds it. If you reverse that magnetizing field you not only get
the field but also the change in magnetic polarity. That change
significantly greater. The other peice of majik is that while you
didn't measure it in that simple rig the current required to magnetize
the nail in the opposite direction is greater than if the magnetic
field in the in the nail was random(zero). This is the characteristic
called hysteresis, IE: to change a field takes more than the amount
needed to maintain or initially estabilish it.
I might have fluffed the grammer and spelling in my hurry to write
this but, thats about it.
Allison
-----Original Message-----
From: John Allain <allain(a)panix.com>
To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org>
Date: Sunday, December 16, 2001 2:02 PM
Subject: Re: [PDP8-Lovers] how to clean a PDP8/A, dishwasher?
>> No need to trace, they are quite regular, you can ohm them. You still
>> need core drivers, sense amps and a dozens of diodes for current
>> steering.
>
>We were thinking what could a person do to see the output from
>just one core bit, not too much more than that... and then work up
>from there.
>
>John A.
>
> From: Richard Erlacher <edick(a)idcomm.com>
> A PC floppy cable certainly wouldn't work with the Little Boards I have,
since
> they use the standard floppy disk cable, which has no twists or cuts.
Take a "modern" PC dual-fdd cable and cut off the end which has the twist
in it.
Glen
0/0
From: Richard Erlacher <edick(a)idcomm.com>
>the "vintage-PC" chipsets were 5 MHz parts, I do believe. That still
wasn't
>rocket-fast, but it was adequate for the 4.77 MHz i8088.
Yes, and NEC and INTEL were selling 8mhz parts before then.
The "PC" was slow by contemporary standards. I'd have likend it to
building
a 2mhz z80 system in 1981, equally poor thing to do.
Allison
