Price/Performance of time

[Jerry Feldman]

Back in the early 1970s Burger King's Manex Point of Sale used a DEC 
PDP-8M. I seem to remember that 1 4K memory board (core memory) cost 
about $5000. With the exception of Connecticut,  each POS had only 4K of 
memory to do full point of sale functions, as well as store hourly 
sales, inventory, cash control, and data communications. In each store, 
the systems would be called by the Miami HQ and would dump the block of 
data. We had power fail, so that if power failed, it would save all of 
its registers (a 12-bit accumulator, a 1 bit link, and a program 
counter).  The modem was very dumb. It had a ring interrupt. The baud 
rate was set in the program. We would simply shift the data to be sent 
into the link, sent a bit, then loop for a 1200 bps interval. Since 
memory on the PDP-8 was 12-bits, we had to keep track of where we were. 
Essentially we would take 2 words, and break them up into 3 words each 
containing 10 bits (8-bits + start and stop). The host in Miami had to 
then reassemble the data. Additionally, we had no I/O devices other than 
the keyboard and Nixie tubes. The keyboard was not ASCII. We had to read 
both the row and column to figure out the key. The printer had 10 
columns. I think we had 5 columns on the drum for digits 0-9. The 
remaining columns had letters, but only 10 letters per column, so a 
Whopper was probably WPR. I rewrite the print routine a few times.
No disk, no tape. If a system had to be reloaded manually, the service 
guy had to bring a punched paper tape reader and the paper tape reader 
board.

At that time the system cost for an entire store was about $20,000 
including 4 registers. Each register could support 2 servers for a 
maximum of 8 servers. The system could only process 1 server at a time. 
When microprocessor systems became available, the cost of these systems 
were about $5000 per store.

-- 
Jerry Feldman <gaf at blu.org>
Boston Linux and Unix
PGP key id: 537C5846
PGP Key fingerprint: 3D1B 8377 A3C0 A5F2 ECBB  CA3B 4607 4319 537C 5846


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