NCR Century 100

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NCRs first all integrated circuit computer. The 615-100 Series integrated a complete data processing system had 16KB or 32KB of short rod memory, 80-column card reader or paper tape reader, two 5MB removable disc drives, 600-line per minute printer. All logic gates were created by wire-wrapping nand gates together to form flip-flops and other complex circuits. The console of the system had only 18 lights and switches. To load a program you entered a hexadecimal boot strap code by setting the rotary switches. This would read a set of four boot cards that loaded the B1 operating system programs from the boot disc.

[edit] Dancing Rods

The memory of the Century Series computers used machine made, short (1/16 inch long and approximately the diameter of a human hair) iron-oxide coated, ceramic rods as their random access memories, instead of the hand-labor intensive core memories that were used by other computers of the time. These rods were inserted into a plastic alignment sheet which was wound with read, write, and sense wire coils arranged in columns and rows. To get the rods to stand up straight on the sheet (so that they would drop into the coils for assembly) a large electro-magnet was turned on and made the rods stand up and ‘dance’ into the individual holes.

[edit] Flying Heads

The removable disc drives were the first to employ floating or Flying heads. The Marketing material made a big thing of this, but there were a number of problems that plagued all of the Century Series systems. Head crashes were common because the head flew less than a human hair's width above the disc surface. And, unless a drive unit was repaired and carefully cleaned after a crash, the next disc pack to load would also crash. If a crashed disc pack was loaded on an operational drive, it could destroy the drive unit.