This is a really trivial question, but I wasn't really a BBC micro hacker
in the old days,
I am planning some upgrdes to a BBC Model B+ (the fact that this
particular B+ lives in the bottom of an Acorn Cambridge shouldn't
matter...). One of them is to combine some of the ROMs (the B+ can take
27256 32K byte EPROMs), thus freeing up some ROM sockets and put a RAM
chip in one of them. I then have to fiddle the write-enable line [1] (should
be easy) and I have 32K of sideways RAM.
The hardware doens't worry me (I have schematics...). But how do I load a
ROM image into the sideways RAM? Is there some loader program I need (and
where do I get it)? Anything I should know about the image file on disk
(anything about the start/end/entry addreeses in the direxctory, for
example)?
[1] I believe it's a good idea to be able to write-protect the sideways
RAM, but I don't want to drill holes in my Cambridge. Has anoyne ever
used the cassette motor line for this? Seems like an obvious thing to use.
-tony
I am trying to figure out what tape drive was used to write some DDS tapes
that I'd like to read. The only clues I have are that they were written
on a VAX of some sort under VAX OpenVMS 5.5-2.
Any ideas?
Thanks!
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
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Hi
Have stumbled over the messages about HP5245, I have one, its
been working for years but now its developed some faults some
of the digits are stuck on a number.Like to have some basic diagrams
before I start fault finding, diagram of the two display boards
decade counter boards would be nice.
Kind Regards Carlo Kowcun (Italy)
Looking for about 10 5.25" blank Apple II or Atari 800 compatible
diskettes...just need something to play around with...
Pete
pbmain(a)wideopenwest.com
Hello,
A friend gave me his first computer to go in my collection.
Its a Challenger C4P. I do have the original manuals etc.
And of course my friend for information.
What I am looking for however is additional information,
websites etc devoted to it. I have the cassette based
version. The first question would be details on the
floppy disk version. IE can I upgrade mine. If not,
sources for programs for the cassette based unit.
Also I remember a program to simulate the cassette player
by using a PC with a sound card. Any one know if that one?
Or should I just make wav files and use media player?
For one thing, I would like a terminal emulation
program for it.
Thanks
Max at
There was an HP3000/922 at MSU Salvage today, with what looked like
a disk cabinet (similar size and shape to the processor cabinet)
and some cables. No idea whether any of it works. No apparent
software or manuals. I may grab it on Friday if it's still there.
If it didn't sell today it should be safe until then, as that's the
next public sale day.
If anyone wants this thing, let me know. I have little enough time
and spare cubic volume in my life without adopting machines I know
nothing about. Someone who already loves this family would make it
a better home.
De
>From: "Bryan Blackburn" <oldcomp(a)cox.net>
---snip---
>
>I may be whacked in the head, but what did the Poly 88 innovate other
>than cuteness? Or maybe that doesn't matter because it is has an s-100 buss?
Hi
Actually it did provide a turning point in micro processors.
It was the first S-100 to have only a power and reset button on the front.
It had a monitor ROM built in that provided a display of memory and
registers, using the memory mapped video. The ROM also had the
tape read code built in. They'd have put the tape write code in
it as well but that was all they could squeeze into the 1K EPROM.
The tape was capable of both Byte format and a high speed ( I forget
if it was 9600 or 4800 ). To write to the tape, one could enter
the program through the monitor. Of course, it made sense to save
that program as your first tape program. The Poly88 had its problems.
cooling was a big issue.
I have two of these, fully operational :)
Dwight
> wanted a TTL based computer, I'm thinking about
> building the Educ-8, http://www.ljw.me.uk/educ8/ , a
> similar TTL based machine described in an electronics
> australia article in 1975. Amazingly, they still sell
> the boards for it, or at least in theory they do, I've
I managed to collect the original magazines with the Educ-8 articles as
well as scans of the articles, and although the boards are available I
am not sure they would all that useful. The Educ-8 was designed around
both 74 and 8 series TTLs. I did some cross referencing, but could not
locate datasheets on all the 8 series ICs used, so I am not 100% certain
that there are pin equivalent 74 series ICs for all. This might mean a
board reroute.
David
>From: "ben franchuk" <bfranchuk(a)jetnet.ab.ca>
>
>Peter C. Wallace wrote:
>> Isn't self modifying code pretty much deprecated these days (aside from
>> trampolines and such)
>
>
>So what is a trampoline?
>> Peter Wallace
>
>
> I have yet to see a good use for self-modifying code. Other than
>subroutines and interupts placing data into a code segement the only
>self modifying code I have seen was for the 8088.
>Ben.
>
Hi
It is interesting that different people have different ideas
as to what self modifying code is. Actually, the ability to
load code and execute from a mass storage is self modifying.
Code that uses a variable value for a table to look up execution
addresses is self modifying. Most every multitasking system
I've seen are self modifying.
I think what people consider dangerous self modifying is
when the program alters the actual execution instructions in
memory and then executes them. It is strange that this form
gets such a large amount of emotional negative response while
other types are hardly considered issues.
No matter how the code is written, one can make bad code in
most any form. One can also make good code as well. There is
no reason why self modifying code should be any more dangerous
than any other type of coding if done with a complete understanding
of what the limitations are. What is the difference between
replacing one or two instructions and then executing them or
replacing an overlay and then executing that overlay? Other
than size, both are doing the same thing. One is forbidden
while the other is normal operation.
Dwight
First: I did not forget the terminals I announced some time ago.
Actually I?m looking for a cheap way to ship them to the fellows who
were interested. As I am quite busy at work at the moment, this will
take some time ? please excuse that.
My main question(s) ? I hope it?s ?on-topic?:
I obtained a nice IBM AS/400 9404 System. It was cheap and is in nice
condition, so I could not resist. It consists of two huge
enclosurements. One (I?ll call it the left one) is loaded with 3 or 4
nice and big harddisks. The second one contains the logic-boards, three
harddisks, an 8 inch diskette and a tape drive. Both boxes have some
batteries built in. The two boxes are interconnected with 3 cables. In
the right box some options(?) are installed:
Fist slot (left): Nr. 2700
Second slot (from the upper position to the lowest): ??? (looks like
the following
), 6151, 6136. Underneath the small modules I can read
2615.
3rd slot: 3120
4th slot: 2533
It?d be nice if you cold help me out a bit with these numbers. I could
not really find out what these are. Could somebody please identify
them?
I also got a 3197 terminal, twinax expansion boxes (2x 4 ports) and
some cables with the machine. My first question: How do I connect the
terminal correctly? I assume it plugs into port 0 for system console.
Are the cables critical, could I use cat 5? I have not enough
connectors
I?d be happy if anyone could supply some cheap connectors
(male) and Infos about the twinax cabling sheme, especially how the
pinout of the connectors and how I have to connect the console
terminal
I have no docs for the machine, but it should be loaded with an OS.
When I turn it on it seems to IPL. Is there any Info available online?
I think, I need some information about the OS too (at the back of the
machine I can read ?Release Level 2? on a sticker. Somebody told me the
OS-License is tied to the machine? If so, could someone provide me some
backup copies of the system disks?
I know most people would throw these machines out, but I want to keep
it as it is one of the earlier AS/400 systems.
I could make pictures if anyone needs it.
Thank you for any information,
Best regards,
Wolfgang
=====
====================================================
Ing. Wolfgang Eichberger cell.: +43-664-240-65-92
http://www.eichberger.org
email: wolfgang(a)eichberger.org
----------------------------------------------------
Gruentalerstr. 24 - 4020 Linz ? AUSTRIA
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