IBM 7072

IBM 7070
Company type	Computer
Industry	Computer hardware
Predecessor	IBM 650, IBM 705
Founded	1958
Successor	IBM 7080, IBM System/360
Products	Decimal-based intermediate data-processing machine

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 initial transistorized stored-program computer, replacing the vacuum tube technology found in earlier models.

Designed to replace both the IBM 650 and IBM 705, the 7070 was not compatible with the IBM 650 instruction set, necessitating a simulator for running existing programs. Although promoted as an upgrade path for the IBM 705, it failed to gain traction due to incompatibilities such as a restricted character set, which led IBM to develop the fully compatible IBM 7080.

Data was stored in words consisting of 10 decimal digits plus a sign, utilizing a two-out-of-five code to represent digits and two-digit codes for characters. The system was available with either 5,000 or 9,990 words of core memory and delivered performance around 27KIPS. Leasing costs were roughly $17,400 monthly, while outright purchase was about $813,000. The machine's weight was approximately .

Subsequent versions included the quicker IBM 7074 (introduced in 1960), which could be expanded up to 30,000 words, and the more affordable IBM 7072 (released in 1961), which operated with slower tape drives. These models were eventually phased out following the launch of the System/360 in 1964.

Architecture

The architecture of the 7070 is word-addressable, with many instructions specifying digit ranges. 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.

Instruction formats generally consist of a signed two-digit opcode, followed by a two-digit index field, a two-digit control field—often representing a field definition—and a four-digit address field.

The system uses Record Definition Words (RDWs) to manage block transfers, input/output processes, and table lookups. A minus sign indicates the final RDW in a sequence; alpha signs are invalid. Each RDW specifies starting and ending addresses for data blocks.

Hardware implementation

Logic and control circuits of the 7070 utilize complemented transistor diode logic (CTDL), whereas timing storage and core storage employ current-mode logic implemented on Standard Modular System (SMS) cards. Approximately 30,000 alloy-junction germanium transistors and 22,000 germanium diodes are distributed across around 14,000 SMS cards within the system.

Input/Output in original announcement

The IBM 7070 family—including models 7072 and 7074—supports diverse peripheral devices such as one IBM 7150 console typewriter; up to four IBM 7300 disk storage units connected via IBM 7604 Tape Control and IBM 7605 RAMAC Control; as many as forty IBM 729 tape drives (models II and IV) interfaced through an IBM 7604 Tape Control; plus six unit-record peripherals (three input devices and three output devices) linked via an IBM 7603 Input/Output Synchronizer and IBM 7600 Input/Output control. The less expensive 7072 model substitutes slower IBM 7330 tape drives instead of the IBM 729 drives used by the other two models.

Mode of operation

Input/output functions rely on lists of Record Definition Words (RDWs), where the last RDW is marked by a minus sign. Each RDW defines the start and end addresses for data blocks.

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

Unit-record equipment—including card readers, printers, and punches—connect through the IBM 7600 Input/Output control via a IBM 7603 synchronizer that buffers card data and print lines. Completion of data transfer between device and buffer triggers priority interrupts; transfers between buffer and core memory stall the processor until finished. These transfers are limited to blocks of up to sixteen words.

The IBM 7150 console typewriter and 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 utilized primarily in various IBM 14xx and 70xx computer models. Offered in versions II and IV, it operates at a recording density of 556 BPI while maintaining backward compatibility with older models at 200 BPI. Subsequent versions V and VI enhanced this capability to 800 BPI. Notably, the 729 drive was not implemented on the IBM 7072 system.

7150 Console Control Unit

The 7150 includes a console typewriter that manages system operations and facilitates communication with programs through the 7600 I/O control unit.

7151 Console Card Reader

The 7151 is a specialized adaptation of a keypunch machine, designed solely for card reading purposes.

7300 Disk Storage Units

The IBM 7300 Disk Storage Unit provided storage capacity equivalent to six million digits. It was superseded by the IBM 1301 model in 1961.

7330 Tape Drive

The IBM 7330 serves as a more economical and slower alternative to the 729 tape drive, supporting dual density formats of 200 and 556 BPI. It was not compatible with the IBM 7070 or 7074 systems.

7400 Printer

Up to three units of the 7400 Printer can be connected via the 7603 Input/Output Synchronizer. This printer produces output in 120-column format at speeds reaching up to 150 lines per minute. The print format is determined by a wired plugboard configuration.

7500 Card Reader

A maximum of three 7500 Card Readers may be linked to the 7603 synchronizer. These devices read standard 80-column punched cards at rates up to 500 cards per minute, with card layout managed through plugboard wiring.

7550 Card Punch

As many as three 7550 Card Punch units can be attached to the 7603 synchronizer, punching data onto 80-column cards at speeds of up to 250 cards per minute. The punch format is controlled via plugboard wiring.

7907 Data Channel

The 7907 is an 8-bit data channel that shares interface compatibility with the IBM 7908 and 7909 channels used on IBM's 7080 and 7090 systems.

1301 and 1302 Disk Storage

Introduced in 1961, the 1301-1 Disk Storage Unit offered a capacity of twenty-eight million characters per module, replacing the earlier IBM 7300. It interfaces through the IBM 7907 Data Channel via an IBM 7631-II File Control unit. The 1302, announced in 1963, expanded this capacity fourfold compared to the original model.

7340 Hypertape

The IBM 7340 Hypertape, launched in 1961, connects through the IBM 7907 Data Channel using an IBM 7640 Hypertape Control unit.

1414 I/O Synchronizer

The IBM 1414-6 Input-Output Synchronizer incorporates six buffers and supports multiple serial I/O devices, including:

The 1009 Data Transmission Unit (modem)
The 1011 Paper Tape Reader
The 1014 Remote Enquiry Units (keyboards and typewriter)
Telegraph input/output devices

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