| The DEC (Digital Equipment Corporation) PDP-11 was a mainstay of academic computing circa 1980. Ours was a PDP-11/35 (see photos below of a similar machine). The screen image at right made for the MADSYS talk says that we had 15 MBytes of disk storage, but I think I was being a bit disingenuous here. Our PDP had two RK05 removable-cartridge disk drives, and each cartridge held 2.5 MBytes. We had 15 MBytes worth of cartridges total, but only two cartridges (5 MByte) could be on-line simultaneously. The tape drive was essential, because there was not sufficient memory to hold the matrices used in least-squares refinement. The matrix was written out to tape as it was calculated, and read back in again in several passes to solve the normal equations. |
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