Thursday, May 29, 2008

Speaking at Defcon 16

After Black Hat, I'll be speaking at Defcon 16 regarding an entirely different subject. The abstract follows.

In 1990, a wire-bound book was published in Paris by the title of «Voyage au centre de la HP28 c/s». It presents a very thorough account of the inner workings of the Hewlett Packard 28 series of graphing calculators. Designed before the days of prepackaged microprocessors, the series uses the Saturn architecture, which HP designed in-house. This architecture is very different from today's homogeneous RISC chips, with registers of 1, 4, 12, 16, 20, and 64 bits in width. The fundamental unit of addressing is the nibble, rather than the byte. Floats are represented as binary-coded decimal, and a fundamental object in the operating system is an algebraic expression.

This architecture is still used, albeit in emulation, in the modern HP50g. With this talk, I intend to call attention to a fascinating, professional, and well-documented feat of reverse engineering. Using little more than their ingenuity and an Apple ][e, Paul Courbis and Sebastien Lalande reverse engineered a black box calculator into a real computer, one which became user-programmable in machine language as a result. More than that, they documented the hack in such exquisite detail that their book is not just a fascinating read, but also veritable holy scripture for anyone trying to write custom software for this machine.

Expect a thorough review, in English, of the contents of the book. This is not a sales pitch; electronic copies of both the translation and the original are free to all interested readers. Topics include the datatypes of the computer algebra system, hacking an upgrade into the memory bus, bootstrapping an assembler, writing in machine language by tables, and adding an I/O port for software backups.

If you'd like a copy of the book in advance, grab the original French from the site of Paul Courbis or email me for a rough draft of the English translation.

--Travis Goodspeed
<travis at>


Travis Goodspeed said...

update: I'm scheduled for 16h00 in the Breakout Room on Friday, the first day of the conference.

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