Wow! Never heard of that before. You described an electromechanical implementation of a software ring-buffer. Amazing.
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com]On Behalf Of Bob Bell
Sent: Saturday, May 02, 2015 6:56 AM
Subject: RE: [N8VEM-S100:6910] Re: Altair Cyclops Info Wanted
Leonard, your comment about shift registers just awakened some very long-term memory.
In the 70’s I was employed just out of high school and during my undergrad years as a bench tech fixing terminals, one particular brand being Wiltek.
These beasts were built to the size of an average office desk. The electronics existed in a card cage inside – about 7 or 8 PCBs each measuring about 10 by 16 inches, all stuffed with SSI and MSI 74xx.
Some of the boards had the shift register memory you mentioned for temporary storage.
But the mass-storage facility was a rather unusual implementation of magnetic tape.
Two continuous loops, each about 50 feet long, of mag tape with cog holes, making it look very similar to 16mm film, were run back and forth through a transport.
The transport was a set of stepper motors that moved the tape under a read/write head, which handled 8 bits at a time.
One loop stored received data and one stored data to be transmitted. This would happen in batches when the mainframe would poll the terminal.
The tape was stored in a narrow channel built into the back side of the desk.
The biggest problems with these machines were all centered around the tape storage:
Driver transistors and damper diodes would go bad, occasionally catastrophically burning holes in the PCB.
Tape heads would wear and need to be refurbished.
The tapes themselves would go bad.
I cannot remember ever having to replace any of the shift register ICs, even though they were early NMOS devices.
I would NOT like to return to those days.
I do, however, remember the Cyclops article and thinking how cool that was (literally – all cameras of that era were tubes!)
Just a kid in school at the time, it was quite over my head and far in excess of my lawn mowing budget.
n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of
Some terminals I worked on years ago used shift registers connected in a loop as memory...
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com]
On Behalf Of John Parsons
A little detective work that
needs a sanity check:
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