some remembrances of UT Austin's CDC 6600
In 1966 I was a senior Math major at UT in Austin. To take classes in which you could learn/use programming, you had to take them as math or science or engineering classes because the UT CS Dept. didn't open until fall of '66, which was after I graduated. To help pay for my math degree I worked as a student computer operator at the UT Computation Center (UTCC) in 1965 and 1966.
Until summer of '66 the "mainframe" we had at UTCC was a CDC 1604. As the predecessor to the UTCC CDC 6600, it featured 48-bit words (eight 6-bit characters/word) and had 32K words of memory composed of tiny magnetic doughnuts commonly called cores. 1604 I/O was via eight Ampex 7-track, pinch-roller (read noisy!) tape drives (200, 556, and 800 BPI). It had no disks and the tape drives had to be PM'ed every AM by one of the two resident CDC engineers. After a successful PM "The Eyes"* was played through the 1604's operator console speaker. Upon hearing "The Eyes", the 1604 operator would know it was time to go to work for the day.
Summer of '66 saw the UTCC installation of the CDC 6600, which replaced the 1604 (and most of its auxiliary equipment, including the Ampex drives). As a UTCC employee I was privileged to help with the 6600's installation (mostly by staying out of the way!). Several more CDC engineers were on hand to accomplish the install. I remember internal wire length as being a critical issue to the optimal functioning of the new machine. As the pics in this article show, there were many internal wires. My recollection is that the 6600 used no integrated circuits; circuitry was implemented in discrete components, hence all the wires and internal cabinet cooling for the circuitry.
Our 6600 had 128K 60-bit words (ten 6-bit characters/word) of memory. I don't remember if that included memory for the ten peripheral processors. At the time, it just seemed incomprehensibly large!
Directly-attached, fast CDC tape drives, drum line printers, card readers and the sexy-in-its-day looking dual CRT operator console gave an enormous boost to UTCC throughput. I don't know how long the 6600 stayed in production at UTCC, but I suspect it was many years because of its superlative utility.
Our 6600 came with a new-to-us type of hardware - disk storage. The disk got everybody's attention, in more ways than one. On the plus side it was way fast; on the minus side its MTBF was way small.
Years later I learned from a CE whose job it had been to keep those disks running, that they were known among the CEs as giant disk brakes! The failure rate proved to be unacceptably short and the failures could be catastrophic, eventuating in a complete mechanical overhaul. Not only would data be lost by these failures, but physically rebuilding the drive could take an unacceptably long time. The read/write heads were hydraulically actuated, which made the head-positioning mechanism complicated and cumbersome to maintain.
After I graduated at the end of the summer of '66 I lost track of the 6600 and its disk problems, but my guess was the hydraulic disk was replaced by another, more reliable disk solution. To its credit the disk was not a CDC product; apparently CDC had arranged with the disk manufacturer to adapt their drive to the 6600.
The promise of supercomputing attendant with the UTCC's 6600 installation was immediately recognized by UTCC staff, UT faculty and students. A mathematical convergence Fortran test program I wrote for a math class ran orders of magnitude faster on the 6600 than on any other computer on campus at that time. In my first job out of college we used a CDC 3150 computer, which was certainly a step up from the old UTCC 1604, but having used the 6600 as a student/employee made me long for my UTCC days on the 6600.
*"The Eyes of Texas", of course.
Biting the hand that feeds IT
