[vcf-midatlantic] Homebrew Computer Systems from Bob the donor

Herb Johnson hjohnson at retrotechnology.info
Fri Jun 25 00:59:24 UTC 2021


On 6/24/2021 5:08 PM, Neil Cherry wrote:
> On 6/24/21 12:58 PM, Herb Johnson via vcf-midatlantic wrote:
> 
> Herb do you have any articles, notes, pointers on ttl/cmos uarts and 
> modems?
> 
> I really think we/VCF should have examples of those and the KC Tape 
> interface for a system of the same period. 

> 
> I think a nice hand built computer with a few ads from the time period.
> Maybe a Trans Am and the price in the ad. It give folks an idea. Also
> something common like a Wonder Bread add and the cost of a loaf of bread. 


https://www.retrotechnology.com/restore/cass_data.html

covers audio-cassette technologies and some related tape tech. Every 
microcomputer that supported cassette tape, documented the format they 
used. I haven't matched brand and model to particular formats like 
Kansas City Standard or other standards.

There was also a *digital* Phillips cassette standard, with digital 
heads and digital media. It was of higher density. Some terminals used 
those schemes, TI for instance.

About modems: I don't cover that so much. I have some real old modems I 
could write up someday. I have some S-100 modem boards, and of course 
all the 80's and 90's computers had modem cards or used external modems. 
I have two boxes of Haynes-class modems to 56K models.And lots of Apple 
Macintosh CS slot modems. Nobody wants them anymore.

About serial and UARTs. (Shrug) Too far down in the weeds, I'm not a 
find-a-chip Web site. Every I/O card with a UART, every computer with a 
UART, is documented somewhere. I do have a document about the radio 
amateurs and their serial networking TCP/IP "packet radio" activities:

https://www.retrotechnology.com/dri/cpm_tcpip.html

I show a progression from ham digital networking through to SLIP and 
PPP, which personal computers used in the 1990's to dial up Unix systems 
to get onto the early Internet. With the advent of WiFi little Arduino 
class boards, all this became of zero interest. (The page is a decade 
old from last update).

There's some "let's BBS" interest today for the modem experience. I"ve 
not kept up with it.

----------------------------

As to the VCFed museum showing this kind of tech, well, they have a 
number of early single-boards and small board-set microcomputer systems. 
Chances are some of them used cassettes. I'm not aware of any "home 
brewed" systems at the chip/board level on display. Some people would 
say that a S-100 system is "homebrew" which isn't quite at the level of 
recent discussion.

I'm sure such an early system is somewhere in the Warehouse because I 
can't *imagine* MARCH or VCFed turning down one that early. That doesn't 
mean I'm right. (The 8008 Mark-8 might qualify but that is a based on a 
particular design and may not be on exhibit, it was a long term loan).

Makes me want to consider, exhibiting just such a system. Not *working*, 
that's a nightmare to restore and boring to operate and observe. One can 
get enough out of it, by reading the specs and docs and looking at the 
hardware.

Regards, Herb the Builder
"can you build it?" "yes, we can!"

-- 
Herbert R. Johnson, New Jersey in the USA
http://www.retrotechnology.com OR .net
preserve, recover, restore 1970's computing
email: hjohnson AT retrotechnology DOT com
or try later herbjohnson AT comcast DOT net

-- 
Herbert R. Johnson, New Jersey in the USA
http://www.retrotechnology.com OR .net
preserve, recover, restore 1970's computing
email: hjohnson AT retrotechnology DOT com
or try later herbjohnson AT comcast DOT net


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