Re: Execution Speed of Early HP Programmables Message #5 Posted by Jim Horn on 27 Nov 2011, 12:55 p.m., in response to message #3 by Katie Wasserman
Early calculators used a bit serial architecture - i.e. the addresses and data were shuffled around only one bit at a time. That's how the '41's RAM and ROM could fit into 8 pin DIPs. So, combine a sub-megahertz clock with having to shuffle 56 bits per register around and then use a lot of internal programming opcodes to do a simple add, combined with having to do GOTOs by searching entirely through memory on the '67, and the slow speed is no surprise.
Of course, a simple counting loop is easy on the Curta. Transcedental math is another thing!
Still, the fastest factoring program on the HP-67 found 10^10-33 prime in about 3 hours 45 minutes, as I recall. The HP-41 was blazingly 3 times faster. Glacial by current standards, but that was over 30 years ago (i.e. the answers arrived 30 years before today's machines can deliver them). And far faster than the personal calculators of 30 years before that...
(An old saying - you can tell the pioneers as they're the ones with the arrows sticking out of their backs).
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