View source for IBM 7070

The '''IBM 7070''' was IBM's first commercial [[transistor]]  [[mainframe]]; first ''announced'' (in September, 1958), as the [[IBM 7090]] beat it to actual first delivery. It was intended for commercial use (as it was built at a time when computers for scientific and business computing used separate [[instruction set]]s).

It was built out of [[Standard Modular System]] cards; the complete machine contained about 14,000 of these cards. It mostly used Complemented Transistor Diode Logic (CTDL), a form of [[diode-transistor logic|DTL]]. [[Main memory]] was [[core memory|core]], either 5K or 10K [[word]]s.

Like its [[vacuum tube]] technology predecessors, the [[IBM 650]] and [[IBM 708]], it was a decimal machine; words were 10 digits long, plus a sign digit. Internally it used a [[two-out-of-five]] code, unlike the 650, which had used [[bi-quinary]] coding; with the higher per-bit cost of core memory, a coding which used less [[bit]]s per digit made sense.

It was not upwardly compatible with its predecessors, however. There was good reason for the 650 incompatability; that machine used a [[drum]] for [[main memory]], and the [[instruction]] format included a 'next [[address]]' field, which was not needed with the [[random access]] [[core memory]] of the 7070. The incompatability with the 708 was harder to justify, and in fact IBM was forced to bring out a compatible [[IBM 7000 series|7000 series]] replacement for the 708, the [[IBM 7080]].

Like the 650, it used a [[serial computer|serial]] [[arithmetic logic unit|ALU]] (digit-serial, not bit-, though), and had three internal word-length [[register]]s in the [[Central Processing Unit|CPU]]; they used [[magnetic field|magnetic]] [[memory]]. Decimal [[floating point]] support was an option.

==Peripherals==

Up to twelve [[magnetic tape drive]]s could be connected to a 7070, via two separate [[data channel]]s; the 729II could read 15,000 characters per second, the 729IV could read 62,500. These drives had a read [[head]] mounted just after the write head in the tape path, to allow immediate checking while writing.

The 7300 moveable-head [[disk]] system could store up to to 6 million digits per drive; up to four drives could be connected, via the same two data channels. Each disk had three sets of heads, to minimize access time.

Up to ten 'manual inquiry stations' ([[printing terminal]]s) could be attached; an interesting innovation, likely one of the earliest [[on-line system]]s.

[[Punched card]] readers and punches were also supported; up to three of each. [[Printer]]s could also be attached, but the maximum count of printers and card punches was three.

==Further reading==

* Charles J. Bashe, Lyle R. Johnson, John H. Palmer, Emerson W. Pugh, ''IBM's Early Computers'', MIT Press, Cambridge, 1986

==External links==

* [https://www.computer.org/csdl/proceedings/afips/1958/5053/00/50530165.pdf The IBM 7070 Data Processing System]
* [https://www.multicians.org/thvv/7070.html The IBM 7070]
* [https://web.archive.org/web/20090805050253/http://www.bobbemer.com/BIRTH.HTM Birth of an Unwanted IBM Computer] (archived)

[[Category:IBM Mainframes]]