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IBM 7074

From Alfawiki
IBM 7070
Company typeComputer
IndustryData processing
PredecessorIBM 650, IBM 705
Founded1958
SuccessorIBM 7080, IBM System/360
ProductsDecimal-based transistorized stored-program computer

IBM 7070 represents a decimal-based intermediate data processing machine introduced by IBM in 1958. As a member of the IBM 700/7000 series, it was IBM’s inaugural transistorized stored-program computer, succeeding the earlier vacuum tube models.

Designed to replace both the IBM 650 and IBM 705, the 7070 was incompatible with the 650 instruction set due to differing memory structures, necessitating a simulator for running older software. Although promoted as an upgrade to the IBM 705, it did not achieve commercial success because it lacked full support for the 705 character set. This shortcoming led IBM to develop the transistorized and compatible IBM 7080.

Data storage utilized words composed of 10 decimal digits plus a sign, encoded through a two-out-of-five coding scheme. The system was offered with either 5,000 or 9,990 words of core memory and delivered performance around 27KIPS. Leasing fees were approximately $17,400 monthly, with purchase costs near $813,000.

The physical weight of the system was .

Later variants included the faster IBM 7074 released in 1960, which could be expanded up to 30,000 words of memory, and the more cost-effective IBM 7072 introduced in 1961 that employed slower tape drives to lower expenses. Both models were eventually replaced by the System/360 line unveiled in 1964.

Architecture

The 7070 operates with word addressing, where many instructions specify ranges of digits. It features a unified address space encompassing both registers and core memory, equipped with three accumulators and 99 index words. IBM’s digit numbering begins at zero for the most significant digit.

Typical instructions contain a signed two-digit operation code, two-digit index field, two-digit control field—often defining a field—and a four-digit address. The system uses Record Definition Words (RDWs) to manage block transfers, input/output operations, and table lookups. A minus sign designates the final RDW in a list; alphabetic signs are invalid. Each RDW identifies starting and ending addresses for a data block.

Hardware implementation

The logic and control circuits of the 7070 employed complemented transistor diode logic (CTDL), while timing and core storage utilized current-mode logic. These functions were realized on Standard Modular System (SMS) cards. The machine contained approximately 30,000 alloy-junction germanium transistors alongside about 22,000 germanium diodes distributed over roughly 14,000 SMS cards.

Input/Output in original announcement

The 7070 series—including models 7070, 7072, and 7074—supported various peripheral devices: one IBM 7150 console typewriter; up to four IBM 7300 disk storage units connected via IBM 7604 Tape Control and IBM 7605 RAMAC Control; forty IBM 729 tape drives (models II and IV) linked through IBM 7604 Tape Control; and six unit-record devices (three input and three output) attached via IBM 7603 Input/Output Synchronizer and IBM 7600 Input/Output Control. The more economical 7072 model used slower IBM 7330 tape drives instead of the IBM 729 drives found on the other two models.

Mode of operation

Input/output procedures depend on lists of RDWs where the final entry is marked with a minus sign; each RDW specifies block start and end addresses.

Each of four I/O channels can connect up to ten IBM 729 tape drives; additionally, four IBM 7300 disk drives attach to the first two channels. These channels function asynchronously relative to the processor and issue priority interrupts when operations complete.

Unit-record equipment such as card readers, printers, and punches interface with the IBM 7600 Input/Output Control through a 7603 synchronizer that buffers data transfers. Completion of data movement between device and buffer triggers priority interrupts; however, transfers between buffer and core memory halt processor activity until finished. These transfers are limited to blocks of sixteen words.

The IBM 7150 console typewriter and the IBM 7501 console card reader connect directly to the IBM 7600 Input/Output Control unit.

729 Tape Drives

The IBM 729 is a seven-track tape drive compatible with most IBM 14xx and 70xx systems. Offered in models II and IV, it operates at 556 BPI but also supports a 200 BPI mode to maintain compatibility with older IBM 727 and 729 model I drives. Subsequent versions, models V and VI, increased the recording density to 800 BPI. The 729 was not utilized with the IBM 7072.

7150 Console Control Unit

The 7150 features a console typewriter that enables system control and interaction with programs through the 7600 I/O controller.

7151 Console Card Reader

The 7151 is a modified keypunch device dedicated exclusively to card reading functions.

7300 Disk Storage Units

The IBM 7300 Disk Storage Unit provides a storage capacity of six million digits. It was superseded by the IBM 1301 in 1961.

7330 Tape Drive

The IBM 7330 serves as a slower and more cost-effective alternative to the 729 tape drive, supporting two recording densities: 200 BPI and 556 BPI. It was not employed on the IBM 7070 or 7074 models.

7400 Printer

A maximum of three 7400 Printers can be connected to the 7603 Input/Output Synchronizer. These printers produce lines of up to 120 columns at speeds reaching 150 lines per minute, with formatting controlled via a wired plugboard.

7500 Card Reader

Up to three 7500 Card Readers may be attached to the 7603 Input/Output Synchronizer. These devices read standard 80-column cards at rates up to 500 cards per minute, with layout configuration managed by a plugboard.

7550 Card Punch

As many as three 7550 Card Punches can connect to the 7603 Input/Output Synchronizer. They punch data onto 80-column cards at speeds up to 250 cards per minute, controlled through a plugboard system.

7907 Data Channel

The 7907 is an eight-bit data channel that shares interface compatibility with IBM’s 7908 and 7909 channels used on the IBM 7080 and IBM 7090 systems.

1301 and 1302 Disk Storage

Introduced in 1961, the 1301-1 Disk Storage Unit delivers storage capacity of twenty-eight million characters per module, replacing the IBM 7300. The unit connects via an IBM 7907 Data Channel paired with an IBM 7631-II File Control. The 1302, launched in 1963, expanded this capacity by four times compared to the original 1301.

7340 Hypertape

The IBM 7340 Hypertape, introduced in 1961, interfaces with an IBM 7907 Data Channel through an IBM 7640 Hypertape Control unit.

1414 I/O Synchronizer

The IBM 1414-6 Input-Output Synchronizer contains six buffer registers and supports multiple serial input/output devices including:

  • The 1009 Data Transmission Unit (modem)
  • The 1011 Paper Tape Reader
  • The 1014 Remote Enquiry Units (keyboards and typewriters)
  • Various telegraph I/O units

This synchronizer connects to the IBM 7070/7074 systems via the IBM 7907 Data Channel Switch, which executes channel programs stored in main memory.

See also

  • IBM 608, IBM’s first fully transistorized product featuring plugboard programming

External links

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