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Bristol’s ‘Big Hex Machine’
Nov. 14, 2016
by Mark Ollig

Yours truly is writing this column the day after the US presidential election.

I noted the sun still rose, the birds still sang, and my coffee still tastes pretty good.

Not too long ago; ok, many years ago, when I attended telephony school in Wadena, we learned about and built several types of electronic circuits; ranging from power supplies to ohm meters.

During the morning class, we learned theory, and traced the currents, resistances, voltages, and power flowing through circuit schematics.

We also worked those lengthy capacitance formulas.

During the afternoons, we paired off in twos in the electronics lab and built the electronic circuits we were taught about in the morning.

Each lab desk had a large wooden “breadboard” and shelves of plastic bins filled with a variety of electronic components, spools of wire, and tools.

The breadboard’s surface was designed as a base for connecting electronic components and wiring of the circuits we built using circuit schematics.

It was a solderless breadboard, which saved us from having to solder the wires to the components.

I later learned about soldering when I worked fulltime at the telephone company during the late 1970s.

Back then, the telephone company used an electro-mechanical, all-relay, analog voice-processing switch.

Installation and maintenance of individual subscriber lines and trunking wiring circuits required the use of rosin core soldering techniques for their connections in the telephone central office.

One subscriber could have 14 separate wiring solder points made to specific terminal blocks located on the wiring mainframe.

My central office soldering days ended in December 1986, when the telephone company installed a new digital central office for processing voice calls.

Instead of wiring and soldering each connection, one could sit in front of a computer display screen and program the subscriber lines and trunks using a keyboard.

But I digress-back to my school days.

Once in a while, a student would sneak over to another lab table’s breadboard and switch the polarity of a DC capacitor.

This action created a large firecracker “pop!” sound when the unbeknownst student turned on their power supply and learned too late their DC capacitor’s polarity had been reversed.

This practical joke caused the other students to erupt in laughter.

Rest assured, yours truly never took part in this electronic delinquency.

After witnessing this prank, I made sure to check my lab’s electronic components before applying power to them.

Today, students at the University of Bristol in the UK are learning in a unique way how computers work.

They and their teacher built a large-sized 16-bit computer with all its cabling and electronic components installed on a plywood sheet using 86-square-feet of surface space.

The plywood is used as a breadboard, and is wall-mounted in their lab for easy viewing and hands-on access.

They called their computer the Big Hex Machine.

This computer processes and programs information via a distinct 16-bit hexadecimal numbering system.

Each single 16-bit hexadecimal number is actually two bytes – as there are 8 bits in 1 byte.

Imagine counting in decimal from zero to 15; which is 16 distinct values.

In hexadecimal, the value also starts with a zero; however the hex 10 equals an A, 11 equals B, 12 equals C, 13 equals D, 14 equals E, and 15 equals F.

I haven’t thought of hex and decimal conversions for a long time, and feel a slight headache coming on.

The Big Hex Machine is being used as “an ultimate teaching tool,” which gives a full and easily seen visual of how the wiring paths are used for connecting the inputs and outputs of the computer’s electronic components.

Its wiring and component modules can easily be traced.

Numerous “hex modules” used with this 16-bit computer include logic gates NOT, AND, OR, and XOR, as well as an arithmetic unit module for making operational logic decisions.

Its non-volatile memory, storing up to 32,768 bytes of information, can retain its data during a power loss.

A web-based application controls how the computer operates.

Students are writing and programming code into this computer, executing it, and observing the results on a custom-built, box-shaped LED matrix screen.

“It’s a result of a great collaboration between students and staff and a real testament to persistence, commitment and teamwork. Most importantly, it’s an achievement of thinking a bit differently,” said Richard Grafton, senior creative teaching technologist in the Department of Computer Science.

The Big Hex Machine is impressive to look at, and provides a great beginner’s hands-on learning tool for students.

I uploaded a couple photos of the Big Hex Machine itself on the wall, and one with two students and a teacher standing in front of it at: http://tinyurl.com/bits-hexmachine.

The University of Bristol can be followed on Twitter via their @BristolUni name.

My non-hexadecimal postings are found using @bitsandbytes.


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