Hi everyone
As a 4th year computer engineering student with a part time job, I
definitely have too much time on my hands, so I've been thinking about
doing something like building my own computer. I remember playing with
the 68k SBCs back in my assembly class, so I thought something from
that family might be an interesting choice. It's ambitious, but
ideally I'd like to do 16/32 bits and a few megs of memory.
Have any of you built something like this? I'm looking for links to
project pages, shared experiences, and advice on what processor to
use. Reminiscence is welcome too, if you have fond memories of such a
thing :)
Thanks
John Floren
--
Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn
Rarest Intel chips in no particular order (from a CPU collector forum; posted in 2005; nobody disagreed):
X8008
G8008
C4040 Purple
C4040 Left Ground Strap
8080B
8080-8
8008
8008-1
MC8080
C4004 W #5 & Ground Strap
ISTR that the 441000s were used in some of the RAM expansion boards for the HP
laserjet Series II printers as well as some of the EMS memory expansion boards.
I probably have a stash of them around here in boards, but it would also
probably take a day of looking to find them :).
> > > Not 411000s - those are 1Mx1s unless I'm quite mistaken. I have a
> > > small pile of those. What I need (as mentioned in the subject line)
> > > is 1Mx4, perhaps known as 441000s, perhaps by other numbers; and I
> > > agree with Keith that they are uncommon in DIP format...
>
>Subject: Re: Commodore PET RS-232
> From: Fred Cisin <cisin at xenosoft.com>
> Date: Fri, 12 Dec 2008 18:22:39 -0800 (PST)
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On Fri, 12 Dec 2008, Dave Caroline wrote:
>> should be a way/was a way to use the 6522 VIA chip it will need
>> translation to rs232 levels though
>
>Does anybody here remember a thread from last month called:
>Re: RS232 voltage level converter box
>
>(trying to figure out what a board with 1488s and 1489s was for)
>
DEC had boards like that for going from TTL to RS232 as modules and
for current loop (TTY) to RS232 or the other way around. There were
a lot of "things" that often had oddball interfaces like Ham radio
tranceivers that could be driven by computer but only had serial TTL.
Allison
tiggerlasv at aim.com wrote:
> I don't have a source for MMJ cables,
> but I do have a US/Domestic source for MMP's
> (the offset modular connectors). . .
>
> http://www.gruber.com/GruberInd/pg.asp?FeatureID=38
>
> They are .14 / each for flat cable, and .41 / each for round cable.
> Last I checked, they don't ship internationally.
>
>
> There are two different styles of DecConnect cables;
> both inverted, and not inverted.?? The only difference
> of course, is that one connector is flipped on one end.
Correct. And excellent info.
> When used with genuine DEC adapters, one?style worked
> for printers (DCE), and the other style worked with terminals (DTE).
Um. No. :-)
Both printers, terminals and computers are DTE.
DTE means data terminal (or terminating) equipment, while DCE means data
communcation equipment. A typical DCE is a modem.
DEC was one of the few companies that actually got this right, and made
cables and connectors that actually followed the standard (well, until
the switched to MMJ anyway, which was a standard of it's own).
If just every computer manufacturer had read the specs, the world would
have been much nicer, but what can one expect from companies who just
didn't put in the effort because of money and lockins (most anyone), or
just was too big to even bother (IBM).
The other company I know of who was pretty good at actually following
the RS-232 standard is HP.
> Back in the early 90's, our office used uVax 2000's,
> connected to VT220's. along with various printers,
> connected using DEC MMJ <> DB25 adapters.
> You couldn't simply swap the DecConnect cables
> because of the inverted MMP's on some of the cables.
> All of our cabling and adapters were unmodified DEC products.
Well, which adapter worked was obviously based on which cable you had. :-)
You still got four combinations, two of which would make you happy.
Johnny
Everyone has seen old monitors/terminals with text clearly burned into the screen, or a grid of fuzzy boxes where the character cells line up, wear from many years of use and abuse. While graphic color tubes can and do develop screen burn (the Macintosh menu bar, and Windows taskbar being commonly found etched into discarded color monitors), the burn-in problem seems more prevelant on older, monochrome tubes.
I use a fair number of old monochrome monitors, and a couple of terminals I use every day. Yesterday, I accidentally left a computer and it's monochrome monitor running unattended for about four hours (I forgot to shut it off/got distracted). When I returned, I carefully examined the areas where text had been on the screen, and could not detect any burn-in, although I can tell that the left side of the display has an oh-so-faint browning to it. Now, I am almost positive that this was there all along, after all - this thing lived a hard life before I found it. But, it got me thinking, how long does text need to be on the screen to burn into a monocrhome tube? Four hours doesn't seem like enough time - otherwise every PC monitor would have the WordPerfect ruler burned into it.
I did some searching, but of course, could only turn up things relating to modern plasma screen TV's, which apparently suffer similar degredation from use.
Were there any studies conducted, or actual ratings for picture tubes like this? The sort of tubes I'm referring to are standard monochrome CRT's, like the ones used in terminals and monitors in the early 80's.
On a similar note, I was playing with a system test utility program for the Commodore PET. It tests the RAM and ROM, loops continuously and displays the test results and running time on the screen. The Commodore PET also uses this sort of monochrome picture tube - and unlike most other machines, you can't shut off just the screen and leave the computer running. So, this test program alternates every second or so between normal and inverse video modes. Now, since the screen is flashing, it shouldn't damage the phosphors - since it is my understanding that the phosphor burn phenomenon isn't so much the phosphors wearing out, but related to them being constantly excited, and therefore heating up and darkening. Is this correct thinking? While I don't plan on running this test for extended periods of time, I do wonder about it's potential effect on the screen, if any.
It's interesting to see what's already burned into screens though, it gives an insight into what the computer used to do. I have terminals with logon promts burned into them, menu systems, and at least one with a dire confidentiality warning permently etched into the tube. I've got a Monitor IIe with "Apple //e" burned into the top - clearly someone left the computer on without a disk in it for a very long time to get that clear of a burn in.
So, like I said, I just got curious about the whole thing, and figured I'd see if anyone else knew more on the subject. Obviously, I always try to be careful and shut things off when I'm not using them, but, you know, mistakes happen.
-Ian
[I tried to send this before, but I don't think it went out. My
apologies if you're seeing this a second time.]
According to my reading, the Burroughs B5000 and Manchester Atlas were
both Harvard architecture machines, and the GE-645 was von Neumann. Am
I correct in my interpretation?
Peace... Sridhar
What options are there for adding an RS-232 port to a Commodore PET? The computer's user port has a different pinout from the C64 (although it uses the same connector), and the port doesn't have the serial output signals the 64 does. Therefore, the quick and dirty hacks that worked great on the 64 to provide serial won't work on the PET.
What communications options exist/existed for the PET, aside from Commodore-produced IEEE-488 modems? Does the ROM include routines to handle such communication, like the C64, or would software need to be created for a particular interface? Is there a teminal emulation software available for the PET?
I have an 8032, and an 8050 disk drive - but of course, the 8050 is completely incompatible with nearly everything else - serial communication would be a big help.
This is new territory for me - the C64, I know. The PET... I'm learning :)
-Ian
