I think this is insanely interesting. The Internet Archive is offering the data from a disk of a Cray-1 read via a robot buily by Chris Fenton:

I managed to acquire a disk drive from the 1970's that could accept one of these disks, but none of the control electronics worked anymore. I built a robot that manually steps the read heads forward, and then I fed the output directly from the analog sensor into an ADC and buffered it using an FPGA, recording ~4 revolutions of the disk for each head/step. I have approximately 55,000 files, each ~650 kilobytes, of the form "head_#_step_#.dat" that each contain a ~67 millisecond snapshot (the disk is revolving at 3600 RPM, so 1 revolution = 16.67 mS) of the digitized output of the analog read sensor. I need to do a fair amount of signal processing to try to recover data on it, but I'd like a way to share the data with others that might be interested in taking a stab at it. ... more »

Ultimately, Fenton got the information off of the disk pack using a whole variety of techniques and experiments, as part of a research project this summer. He wrote a paper about the process, entitled “Digital Archeology with Drive-Independent Data Recovery: Now, With More Drive Dependence!” and it’s now mirrored here at the archive. If nothing else, be sure to browse through the paper just to see the customized stepper motor and reader he build to pull the magnetic data off the platters. And I was kind of understating things... ultimately he did hook it up to USB. ... more »

One of the coolest aspects of this machine is that everything is fully pipelined. This machine was designed to be fast, so if you’re careful, you can actually get one (or more) instruction every cycle. This has some interesting implications – there’s no ‘divide’ instruction, for instance, because it can take a variable amount of time to finish. To perform a divide, you need to first compute the ‘reciprocal approximation’ (something we *can* do in exactly 13 cycles, it turns out) of the denominator value, and then perform a separate multiply of that result with the numerator. ... more »