The description of the 6205 module is correct. I think Wikipedia exaggerates the fear of powering off a PDP-6, but perhaps others would like to vote on that. Another aspect of the 6205 is that the clock speed was getting into the range where reliability really required design as a radio frequency (RF) device, such as having a good ground plane, but this fact hadn't fully sunk in with the designers. Consequently, the noise margins were sometimes pesky, and sometimes a given 6205 would work in one slot but not in another, as I remember. One programmer that did a lot of the PDP-6 floating point library was former MIT student and TMRC member Clark Frasier (spelling?). I think he coded many of the trig functions. He might remember about sqrt, even if he didn't code it. -- Mike ----- Original Message ----- From: "quad" <quadricode@gmail.com> To: "math-fun" <math-fun@mailman.xmission.com> Cc: <rcs@xmission.com> Sent: Friday, April 15, 2011 8:21 PM Subject: Re: [math-fun] Origin of SQRT hack?
As a quick aside, Wikipedia says
"The PDP-6 was infamous because of the 6205 board, a large (11 x 9 inches) board which contained 1 bit of AR, MB, and MQ (thus there were 36 of these). It had 88 transistors, a 2-sided PC etch, two 18-pin and two 22-pin connectors (two on each side of the module). Because of all these connectors, swapping this module was a major undertaking, and the mechanical coupling made it highly likely that fixing one fault would cause another."
following with
"There was also a great fear of powering off a PDP-6, since it would generally result in at least one 6205 board failing."
Is this true?
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun