Hey all! So, I've found myself studying up on RS-232 this year for a few
reasons.
I'm mulling over doing an RS232 themed talk at June VCF. Not a super
exciting topic, but I do think that RS232 has an interesting history: In
the SAGE relationship, and as a follow up to (essentially) prior telegraph
communication.
From what I've read, "50 baud" was a kind of an initial goal to beat, since
that's what the top telegraph operators could achieve (in small burst,
probably not all day). And those operators did have to also deal with
things like start/stop "bits". Maybe it wasn't an intentional goal, but
just that it establishes why "50 baud" is generally the lowest we ever see
mentioned (or, if you go slower than that, might as well use the older
tech).
Then 75/110/130 baud to have digital-systems interoperate with classic
mechanical teletypes. Going any faster and those systems jam up or
overheat? These weren't yet called "serial ports", so I'm not sure what a
late 50s system would even call their equipment that facilitate this data
exchange (since I'm not sure what kind of crystal-clock they even had
yet).
Then, was it the SAGE program that demonstrated the idea of doing this kind
of data exchange across copper phone lines? That is, the idea of computers
collaborating not just in a room, but across long distances (miles)? And
doing so by using an audio tone presentation? (they settled on around
3100MHz, which ended up translating to 300 baud? hence, that's basically
why the first digital to digital system data exchange settled on that baud
rate, which was reliable on both 50 and 60Hz power systems, and
meaningfully faster than prior 110 baud - so a good milestone to turn it
into a product, which was the Bell Model 103?).
I couldn't find much details (like a manual) on the Bell 101 equipment
(anyone seen one or have a manual?). But I did find the Bell 103 manual -
the photo of its innards is grainy, so I don't understand how the Bell 103
did 300 baud without a UART (and one of the pinout lines I see did run
power, so not sure if that's-yet RS232 or not; I know RS232 was evolving
right at that same time circa 1962). I've about the 1970ish TR1402
initial DIP UART, with anything prior being an experiment (like a full
board concept by DEC).
I know from 1962, both RS232 and ASCII standards still took maybe another
decade to really gain traction as standards (at least, from what I've
read). Getting the world to comply with any standard always takes a lot of
effort (for a practical reason of everyone still having invested in the
older tooling that was still functional). But it's interesting how those
two standards are still in use (not in their original form, but least the
1967 revisions) - extending from Baudot.and late 1800s-tech on telegraphs.
Does anyone know of any grocery stories using RS232 in the 1960s? I think
barcode scanning was just introduced in that era. I can just imagine a
smart grocery store owner, in the backroom programming their minicomputer
for payroll and inventory management. In FORTRAN and without a CRT?
Actually, in the 60s, I think included software would be negotiated with
the provider of the computer (well, I'm not sure how that differed between
minis and mainframes).
I know early microcomputers used RS232 for keyboards (1974-1976 era). The
IBM PC keyboard is essentially another form of serial.
Well, sorry for the rambling - have other RS232 related questions, but
first wanted to focus on the historical aspects (and see if I'm somewhat on
the right track at least).
-Steve
Microsoft, or is it Micro-Soft or MICROSOFT, is a 50 yr. old trans-national
corporation. Whether it has been good or not-so-good for society is
debatable but on the financial-side its been very kind to investors(the
earliest ones anyways). Capitalism certainly owes Microsoft a good nod!
Happy computing.
Murray 🙂
Follow-up:
Vendor now on eBay for Fairchild 75325DC in lots-of-five; they accepted my
Best Offer.
https://www.ebay.com/itm/333675901157
So now I can get back to making some progress on repairing the H222A in my
MM11-DP :-}!
From: pbirkel(a)gmail.com
Sent: Friday, March 11, 2022 10:01 AM
To: General Discussion: On-Topic Posts <cctech(a)classiccmp.org>
Subject: Seeking a MC75325L Dual Memory Driver
I have here in my hands a DEC H222A (16Kx18), part of a MM11-DP, that took a
blow at sometime in the past. In consequence there are a number of small
parts damaged (snapped diode, crushed axial electrolytic, chipped mica
capacitor, cracked/broken SIP resister net) but those all appear to be
relatively easy to replace.
What's not so easy to replace is the MC75325L Dual Memory Driver (L =
Ceramic) that was de-lidded in the process :-<.
I am wondering whether anyone has one of these ICs in their spare parts
drawer that I could acquire?
I do see a MC75325P (plastic) on eBay at littlediode_components for ~20USD,
plus a surprisingly modest shipping charge (Royal Mail International).
UTSOURCE claims to have a supplier of the ceramic part "new", with a
significantly higher shipping charge.
Before I go with the ceramic part (IMO not the sort of packaging that gets .
remarked) I thought that I would check here for alternative sources.
Thank you,
paul
I prefer to use the Daily Digest mode. Then you can quickly glance at the topics and decide whether it is worth reading any particular messages. The pain comes when you may want to contribute something, as then you need to reconstruct enough of the message of concern in a new composition and reply that way.
Kevin Anderson
Dubuque, Iowa
Message: 3
Date: Thu, 23 Jan 2025 08:44:29 -0700
From: ben <bfranchuk(a)jetnet.ab.ca>
Subject: [cctalk] Re: AI? Really?
On 2025-01-23 8:15 a.m., Alexander Schreiber wrote:
On Tue, Jan 21, 2025 at 12:52:49PM -0700, ben via cctalk wrote:
On 2025-01-21 10:54 a.m., Paul Koning wrote:
Uh, what? How would the earth surface gravity be that much different? "Citation needed" as Wikipedia would say.
paul
https://en.wikipedia.org/wiki/Autodynamics
Ah, crackpot nonsense: "mainstream physicists have considered autodynamics
a crackpot theory for decades" - which is right there on the Wikipedia
page.
Kind regards,
Alex.
How lucky I am that I am not a "mainstream physicist".
A true scientist looks at the evidence, not what is discussed by others.
I also like the expanding earth theory, vs continental drift.
Where is all that energy to move the plates around.
The answer to your question is one that even mainstream physicists (Lord Kelvin) have gotten wrong in the past. See https://www.americanscientist.org/article/kelvin-perry-and-the-age-of-the-e…
A little humor for the group.
Among my other "legacy" systems I also have and still fool around
with a bunch of TRS-80's. Believe it or not, the Z80 based TRS-80's
were among the systems for which a version of STVOS was available.
Thought I would look to see if any of it was still floating around.
Asked Google
"TRS-80 Software Tools Virtual Operating System"
Got this result at the top of my response generated by whatever AI
engine they use.
--------------------------------------------------------------------------
A "TRS-80 Software Tools Virtual Operating System" refers to a software
program that allows a modern computer to emulate a vintage TRS-80
computer, essentially creating a virtual environment where you can run
old TRS-80 software, including operating systems like TRSDOS, by
simulating the hardware and functionality of the original machine,
letting you access and use programs designed for the TRS-80 on your
current computer.
---------------------------------------------------------------------------
That is the biggest pile of steaming poo I have ever seen come out of
any of the various AI engines I have run into. Not one piece of it is
accurate other than the mention of TRSDOS.
I also have a bunch of iRobot Roombas in my house. Based on my
experience with AI and robots I think there is no chance we will
have to worry about any Terminators in the future.
bill
Hi Folks!
Anyone have one or more of the old TI CPUs? The usual suspects don't
stock it (Unicorn, Abra, Jameco...). I have a customers game board in
where the CPU was backwards and previously destroyed...
In case anyone is curious the game was from Japan - Universal's COSMIC
GUERILLA.
This is NOT the TMS9918A - video chip - that some folks are trying to
emulate with Raspberry Pi(e)s.
Thanks!
John :-#)#
--
John's Jukes Ltd.
7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
Call (604)872-5757 (Pinballs, Jukes, Video Games)
flippers.com
"Old pinballers never die, they just flip out"
How much for the quadra VRAM and how many are there?
-----------------------------------------From: "Juan del Pino via
cctalk"
To: cctalk(a)classiccmp.org
Cc: "Juan del Pino"
Sent: Tuesday January 21 2025 11:24:00AM
Subject: [cctalk] Ram and vram
Hello, people:
anyone interested?
hitachi hb56a19a. 150
TC514400ASJ-70
256KB VRAM Apple Macintosh Quadra 700 900 950 68-Pin SIMM RAM 70ns
MT42C8128DJ-7 50
IBM Memory Ram 4MB 1M x 32 B1D1320BA-7
DRAM SIMM 72 PINES 60NS 16MB TI TMS417409ADJ-2E. x2
Thanks
