One method that I have used for years with equipment that blows fuses is to
put a light bulb in line with the incoming power. Depending on the actual
correct load of the equipment determines the wattage of the bulb needed. On
normal operation the bulb will light to about 1/4 to 1/2 of normal then dim.
(typical inrush - charging caps.) If the bulb lights near fully it is
taking the load instead of blowing the fuse. At this time you can use a
meter and find the defective component. Usual caution applies the equipment
is floating if the bulb is in line with neutral.
Dan Burrows
dburrows(a)netpath.net
-----Original Message-----
From: John Foust <jfoust(a)threedee.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Thursday, October 08, 1998 12:30 PM
Subject: Re: Apple power supply problems
>At 08:34 AM 10/8/98 -0700, Marvin wrote:
>> Running it a short time with
>>the fuse shorted out heated up the chip and I was able to feel where the
>>problem was. Troubleshooting vs normal operation :).
>
>And sometimes when you do that, the dead chips will notify you
>of their new condition by blowing their tops.
>
>- John
< seems though, everybody wrote assembler code so that either the s/w chec
< to see which processor was used or wrote straight 8080 asm code to just
< cover everybody without having the extra CPU checking code taking up spa
< Most commercial language interpreters and compilers, especially from Hea
< handled 8080-based machines for sure.
Generally true but, not absolutley so.. however some bios used Z80 code
to do disk io or used 8080 code tricks that do not run on z80.
Come from having aboth an 8085 powered s100 (explorer 8085) and a slew of
z80 systems.
< Allison, for the H8 there were at least two third-party Z80 CPU boards m
< (I can look up the mfgrs if anybody wants) and a Heath-made Z80 board.
I'm well aware of them and helped several friends bring them up.
< Early on when the Z80 became rather popular, the original 8080 CPU boar
< was of course found to be lacking in performance compared to the TRS-80'
< N*, Kaypros, various S100's and other contemporary CP/M Z80 machines.
< Hence, the little cottage industry, so to speak, which sprang up to dea
< with making Z80 boards. A 4 MHz CPU by DG Micro (I think that's the name
I went to z80 in early 1977 as the 8080 already had a case of impending
doom being limited to 2mhz and fewer instructions. The better instruction
set of the z80 was enough in itself.
< really was a performer up against many other machines. The H-89 was a Z8
< machine when it first was introduced around 1980 or thereabouts.
Yes, h89 was mid 1980, by then the z80 had permutated the software
for cpm systems. Consider that S100 system ahd all pretty much gone
z80 by 1978 and the few non z80 systems were either dual processsor
like Compupro 8/16 or oddball the Autocontrol AC85 (8085/5mhz). The
ZCPR CCP replacement and widespread use of z80s made for major software
like languages to be 8080 compatable at the expense of performance
while the system would have a bios written using z80 extended.
Allison
< I seem to recall that one (or more) of the Godbout/CompuPro ram boards u
< a 2kx8 static RAM part that had the same pinout as a 2716 EPROM, and cou
< support 2716s in place of some/all of the RAM chips. True or false?
Ram16 and RAM17 both used 6116 2kx8 but neither were configurable for
2716 Eproms. It can be done but it would be a hack.
Allison
Below is a description of a system with some data to be rescued.
I've already responded to the people mentioned, so there's no need
to respond again. I asked for more details, if they had any:
when was it used, what software did it run, whether the disk is
soft- or hard-sectored.
I have no idea, though, what kind of system this was. Does "AES"
ring a bell with any Canadian readers?
- John
>>Sent from: Gilles Poitras <cowpunk(a)sirius.com>
>>
>>This is from a mailing list for theological librarians that I am on.
>>
>>Can anyone help out?
>>
>>>"Accelerating obsolescence" strikes again.
>>>
>>>Professor Dr Hans Rollmann, who supervises one of the more elegant and
>>>elaborate sites on the WorldWideWeb for the Department of Religious Studies
>>>at Memorial University in Newfoundland, has found some important primary
>>>data that he hopes to mount with other texts on the site. These data are
>>>imprisoned on 8-inch computer disks that were made on an AES computer,
>>>apparently in the 1980s. No printed record of the material survives; only
>>>the 8-inch disks remain. No AES computer or 8-inch drive exists at Memorial
>>>University; the technical services people from the Computing Sciences
>>>Department tried to build an 8-inch drive from spare parts, but came up
>>>short. The intellectual content frozen in this "obsolete" technology
>>>remains unreadable.
>>>
>>>Does anyone know the whereabouts of an intact AES computer? Failing that,
>>>is there any available information about these machines? What did the
>>>acronym AES stand for? Where was it built? Most important, what operating
>>>system did it use? What word processing software might have been loaded?
>>>
>>>Has anyone preserved any computer with an 8-inch disk drive? As I recall,
>>>both Commodore and Atari used 8-inch drives.
>>>
>>>Anyone who has useful information on this problem can communicate with
>>>Professor Rollmann at
>>>
>>> hrollman(a)morgan.ucs.mun.ca
>>>
>>>Those who may be interested in his religious studies web site can begin
>>>sifting through its many layers at
>>>
>>> http://www.ucs.mun.ca/~hrollman
>>>
>>>Professor Rollmann will be grateful for any assistance anyone can offer.
>>>The rest of us need to be sure that any intellectual material we
>>>"catalogue" can also be "read."
I have a manual for the N* HRAM series which I'd be happy to copy and send
you - email me. There are some differences between revision B and E boards
and there are lots of jumper options. In summary, S1 and S2 select the
active memory areas, JP1 selects the bank status on reset and selects I/O
control bits for bank switching and parity, JP2 selects areas to be bank
switched, JP3 selects the parity error response, JP4 implements the First
Quadrant option (only revision E 48K version), and JP6 is reserved (no
jumper).
Bob Stek
bobstek(a)ix.netcom.com
Saver of Lost SOLs (and the occasional Horizon)
Hi Jim and all,
At 10:50 PM 10/7/98 -0700, you wrote:
>Can anyone confirm this vague memory, or set me straight?
>
>I seem to recall that one (or more) of the Godbout/CompuPro ram boards used
>a 2kx8 static RAM part that had the same pinout as a 2716 EPROM, and could
>support 2716s in place of some/all of the RAM chips. True or false?
>
>And if true, was there any special configuration that needed to be done for
>the 2716s?
>
A 6116 is a 2kx8 static ram. The only difference in its pinout from a 2716
is pin 21. For the 6116 it is /write enable (active low). For the 2716 it is
V(program). For read it is tied to 5V, it needs a higher voltage and
current, up to 5mA, so just a TTL "1" isn't enough. Can you jumper this pin
to +5 volts?
-Dave
Hey, several threads just coalesced in my head. (Ouch!)
There are a handful of questions that keep getting re-hashed.
Build my SwTPC kit and play with it, or treasure it in pristine form?
Is my LSI-11 a micro, or not?
Are my XT's really classic?
Should I hack my Apple-1 to sub in a 99 GHz Pentium for the 6502?
Wanna buy a 1200 baud modem?
The problem is that we have so many different backgrounds and goals,
everybody has different answers to those.
So, when these questions come up, maybe instead of arguing about the
right answers, we could gain more by digging backwards to the *reasons*
for the different answers.
Here are my two cents:
Most of my stupid sample questions revolve around differing valuations.
Sources of value.
1. Nostalgia
I had/wanted one of these once.
2. Education
This is really different from stuff I already know.
3. Preservationism
There are only three left on the entire planet.
If I don't protect it, soon there won't be any.
4. Usability
I make practical use of it.
5. Money
There are only three left on the entire planet.
Somebody must be willing to pay a lot for it.
.. any more?
So building a Heathkit is good for reasons 1, 2, and 4; and bad on 3 and 5.
In my own collection, different items hit different buttons. I play
games on my Radio Shack Color Computers, so they hit button 4. I also
hack around in machine code on them, so they hit button 2. And I've done
quite a bit of work with 6809's, so they hit button 1 as well. (No wonder
I have such a pile of CoCos!) My SwTPC kit is still unbuilt for reason 3.
It doesn't hit buttons 1 or 2 so hard because I also have an assembled one
which covers those nicely. (Man, I'm a lucky guy!) And it seems my own
button 5 isn't connected to anything. But other peoples' seem to work
just fine.
The one sample question still unanswered is a definition thing. So maybe
the root question should be, why is one definition better than another?
I learned the definition of microprocessor to be a single-chip CPU, and
a microcomputer to be a computer based on a microprocessor. But I never
questioned it. Why is that a useful definition?
Maybe it is a measure of how hard it would be to build a system around
it. Which in turn could be correlated with cost, and so with popularity.
By that reasoning, if you get the same functionality out of a smallish
chip-set as a single chip, and the price is the same, both should be
considered as micros.
Or maybe it has more to do with physical size of the end result; if you
have a single chip instead of four, it leaves you with more room to put
the rest of the computer on that same PC board. Maybe that could be
really important for hobbyists. (I know my own attempts at homebrewing
were all SBC's.)
But there is a red herring in all this. External VLSI support chips
are a convenience. You could have built an 8080 system without the 8228.
You would just use a boatload of TTL instead. So again, the issue is
probably just cost of doing so (money, time, space). Was the 8080 more
expensive in any way because of the 8228's existance? No. Was it any
less of a microcomputer? Either the 8228 was enough of an improvement
over the boatload of TTL that it made 8080 systems doable (ie, made it a
micro), or maybe the lack of the 8228 circuitry in the 8080 chip itself
still made it impractical for some (ie, made it a non-micro). It depends
on where your thresholds are. You can still argue about whether or not
the 8080 without an 8228 is a complete CPU, but my point is that this may
not be worth arguing. What is the practical impact of having the entire
CPU on one chip vs. two? How does it change anyone's behaviour? *That*
could be worth some discussion.
I have my own ideas about which things are micros and which are not, but
in retrospect, the definition that I was taught is not a useful one; it
does not classify things into categories that I can use to any benefit.
Cheers,
Bill.
>I seem to recall that one (or more) of the Godbout/CompuPro ram boards used
>a 2kx8 static RAM part that had the same pinout as a 2716 EPROM, and could
>support 2716s in place of some/all of the RAM chips. True or false?
True! The part is the Hitachi (or compatible) 6116P-2.
>And if true, was there any special configuration that needed to be done for
>the 2716s?
It depends on the exact board; most boards that would take either had
a jumper per socket to set RAM vs EPROM. Which board are you specifically
interested in? When I bought out the stock of the last remaining
Compupro dealer I ended up with most of the manuals in addition to
hundreds of boards...
This feature certainly wasn't confined to Compupro; there were several
dozen other manufacturers of memory boards that did this, too. Most
of the time the jumpers are pretty obvious, though some weren't below
requiring the user to do PC board surgery.
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology Voice: 301-767-5917
7328 Bradley Blvd Fax: 301-767-5927
Bethesda, MD, USA 20817
> Is there available on the Web this info?
Probably, but the authoratitive source for this sort of thing is
the manual that matches the version of RT you're interested in.
> Also, I have an 11/73 with RT-11SJ V5.0.... it has an 8" drive.
>What would I have to do to make a bootable minimal floppy on this
>machine? In other words how few files can one get away with to wake
>up a PDP11 with only an RX02 clone as it's mass storage?
That's easy: SWAP.SYS, TT.SYS, DY.SYS (or DX.SYS or whatever driver
your hardware uses for the 8" drive), and a monitor (RT11SJ.SYS). This
gives you a bootable minimal floppy which is capable of doing very
little :-). Almost certainly you want to put PIP, DIR, DUP, FORMAT,
and other useful "recovery utilities" on as well (BUP if you use it,
your favorite editor, etc.). And certainly the
drivers for any other devices you may be interested in.
And, of course, after putting the files on the floppy, you want to make
it hardware bootable too! COPY/BOOT DY:RT11SJ DY:, for example.
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology Voice: 301-767-5917
7328 Bradley Blvd Fax: 301-767-5927
Bethesda, MD, USA 20817
