# IBM 7070

IBM 7070 is a decimal-architecture intermediate data-processing system that was introduced by IBM in 1958. It was part of the IBM 700/7000 series, and was based on discrete transistors rather than the vacuum tubes of the 1950s. It was the company's first transistorized stored-program computer.
The 7070 was expected to be a "common successor to at least the 650 and the 705". The 7070 was not designed to be compatible with the 650 instruction set, as the latter had a second jump address in every instruction to allow optimal use of the drum, something unnecessary and wasteful in a computer with random-access core memory. As a result, a simulator was needed to run old programs. The 7070 was also marketed as an IBM 705 upgrade, but failed miserably due to its incompatibilities, including an inability to fully represent the 705 character set; forcing IBM to quickly introduce the IBM 7080 as a "transistorized IBM 705" that was fully compatible.
The 7070 series stored data in words containing 10 decimal digits plus a sign. Digits were encoded using a two-out-of-five code. Characters were represented by a two-digit code. The machine shipped with 5,000 or 9,990 words of core memory and the CPU speed was about 27KIPS. A typical system was leased for $17,400 per month or could be purchased for $813,000.
The 7070 weighed 23,150 pounds (11.6 short tons; 10.5 t).
Later systems in this series were the faster IBM 7074 introduced in July 1960 and the IBM 7072 (1961), a less expensive system using the slower 7330 instead of 729 tape drives. The 7074 could be expanded to 30K words. They were eventually replaced by the System/360, announced in 1964.

## Architecture

The 7070 is word addressable but many instructions can specify a range of digits. It has a single address space for registers and core storage. It has three accumulators and 99 index words. IBM numbers digits starting with 0 for the most significant digit.
Instructions on the 7070 typically have a signed two-digit opcode, a two-digit index field, a two-digit control field and a four-digit address field. In many instruction the control field is used as a field definition.
The 7070 uses Record Definition Words (RDWs) for
* Block transmission
* Input/Output
* Table lookup
A minus sign indicates the last RDW in a list; an alpha sign is invalid. Each RDW contains the starting and ending address for a block.

## Hardware implementation

The 7070 was implemented using both CTDL (in the logic and control sections)$^{:167}$ and current-mode logic (in the timing storage and core storage sections) on Standard Modular System (SMS) cards. A total of about 30,000 alloy-junction germanium transistors and 22,000 germanium diodes are used, on approximately 14,000 SMS cards.$^{:167}$

## Input/Output in original announcement

The 7070, 7072 and 7074 support a variety of peripheral devices. including up to 1 7150 console typewriter, 4 7300 Disk-Storage units attached to an IBM 7604 Tape Control via an IBM 7605 RAMAC Control, 40 729 models II and IV tape drives attached to an IBM 7604 Tape Control, and 6 (3 input, 3 output) unit record devices attached to an IBM 7603 Input/Output Synchronizer via an IBM 7600 Input/Output control.

### Mode of operation

Every I/O operation uses a list of Record Definition Words (RDWs); the last RDW in the list has a minus sign. Each RDW has a beginning and ending address.
Ten 729 tape drives can be attached to each of 4 I/O channels. Four 7300 disk drives can be attached to the first two channels. The channels run asynchronously to the processor and generate priority interrupts upon completion of an operation.
Unit-record devices (Card readers, printers, punches) are connected to a 7600 Input/Output control via a 7603 synchronizer that buffers cards and print lines. Completion of a transfer between the device and the buffer generates a priority interrupt. Transfers between the buffer and core storage delay the processor until completion. Transfers are limited to 16 words.
The 7150 console and 7501 console card reader are connected directly to the 7600 Input/Output control

### 729 Tape drives

The IBM 729 is a 7-track tape drive common to most of the IBM 14xx and 70xx computers. It is available as a model II and a faster model IV. The models II and IV normally record at 556 BPI, but they support 200 BPI for compatibility with the older IBM 727 and 729 model I. The models V and VI, supporting 800 BPI, were announced later. The 729 is not used on the 7072.

### 7150 Console control unit

The 7150 includes a console typewriter that both controls the system and communicates with the running program via the 7600 I/O control.

#### 7151 console card reader

The 7151 console card reader is a modified keypunch that can only read.

### 7300 Disk Storage Units

The IBM 7300 Disk Storage Unit has a capacity of 6 million digits. The IBM 1301 replaced it in 1961.

### 7330 Tape drive

The IBM 7330 is a slower, less expensive, alternative to the 729; it is not used on the 7070 or 7074. Like the 729 II and IV, the 7330 supports dual (200 BPI/556 BPI) density.

### 7400 Printer

Up to three 7400 Printers can be attached to the 7603 Input/Output Synchronizer. The 7400 prints 120 column lines at up to 150 lines per minute. The installation must wire a plugboard to control the layout of the print line.

### 7500 Card reader

Up to three 7500 Card readers can be attached to the 7603 Input/Output Synchronizer. The 7500 reads 80-column cards at up to 500 cards per minute. The installation must wire a plugboard to control the layout of the cards.

### 7550 Card punch

Up to three 7550 Card punches can be attached to the 7603 Input/Output Synchronizer. The 7550 punches 80-column cards at up to 250 cards per minute. The installation must wire a plugboard to control the layout of the cards.

## Additional or optional I/O units
### 7907 Data Channel

The 7907 is an 8-bit channel with the same interface as the 7908 and 7909 channels on the 7080 and 7090.

### 1301 and 1302 Disk storage

In 1961, IBM announced the IBM 1301-1 Disk Storage Unit, with a capacity of 28 million characters per module, replacing the IBM 7300 Disk Storage Units. The 1301 attaches to an IBM 7907 Data Channel via an IBM 7631-II File Control.
In 1963, IBM announced the IBM 1302, with quadruple the capacity of the 1301.

### 7340 Hypertape

In 1961, IBM announced the IBM 7340 Hypertape. The 7340 attaches to an IBM 7907 Data Channel via an IBM 7640 Hypertape Control.

### 1414 I/O Synchronizer

* IBM 1414-6 Input-Output Synchronizer contains 6 buffers and can attach a variety of serial I/O devices:
** 1009 Data Transmission Unit (modem)
** 1011 Paper Tape Reader
** 1014 Remote Enquiry Units (keyboards and typewriter)
** Telegraph I/O units
The 1414-6 is connected to 7070/7074 via the IBM 7907 Data Channel Switch. The 7907 can execute channel programs from the main memory of the 7070.