Ishii Yoshiteru, Saito Masato, Yamada Akihiko, and others started developing the NEAC-2204 in 1960. The first unit was completed and shipped in September 1961.

The NEAC-2204 took the online, real-time processing and multi-program processing developed for the NEAC-2202 and added stored-program memory and file and I/O devices. The NEAC-2204 was able to execute seven separate programs simultaneously through CPU time-slicing with its stored-program memory. The developers used a magnetic drum for the main memory, since cost concerns outweighed performance, but they balanced this with the computation speed by using magnetic core buffer memory as cache memory. The NEAC-2204 could control up to seven I/O devices simultaneously thanks to a time-division methodology. Therefore, the computer supported many different I/O devices, including the NEAC-Writer, photoelectric tape readers, high-speed paper-tape punchers, card I/O devices, and high-speed teletypewriters.

The NEAC-2204 was designed to use inexpensive, high-capacity magnetic tape for data file maintenance. Part of the magnetic drum was used as a buffer to mitigate the speed differential between the computer and the tape.

The first unit was installed in the basement of Yamaichi Securities’ Fukuoka branch with the terminals located in the first floor office. During the day, the computer was used online to process securities transactions and afterhours it was left to batch process statistics and reports. In its own way, the NEAC-2402 was the harbinger of online banking.

Specifications of the NEAC-2204
Completed September 1961
Computation method Control method Fixed-point, serial, base10 Stored-program memory
Logic elements transistors 350
diodes 7,000
magnetic cores 360
Word structure Numeric words 12 digits in base10 + sign (1 bit)
String words One character (kana or symbols) represented with 2 digits
Instructions 3 1/2 addressing system
14 index registers
Computation speeds(using magnetic core memory) Addition and subtraction 1.5 ms
Multiplication 33.5 ms
Division 38.75 ms
Internal storage unit (core) Magnetic drum Main memory: 3000 words average call time: 13.7 ms
Loop memory: 100 words average call time: 3.7 ms
Magnetic core Loop memory: 100 words average call time: 3.7 ms
Magnetic tape unit Magnetic tape units: up to six
Read-write speed: 120 words/second
One reel: 380 meters long with a capacity of 100,000 words
I/O units Photoelectric tape reader 200 characters/second, up to four units
High-speed paper-tape punch 50 characters/second, up to four units
High-speed teletypewriters 200 characters/minute, 120 characters/line (with a 96-character set)
350 characters/minute, 120 characters/line (with a 48-character set)
Up to three units of either type
Card readers 200 cards/minute, up to three units
100 cards/minute, up to three units
NEAC-Writer 100 cards/minute, up to seven units
Print speed: 560 characters/minute
Punch speed: 560 characters/minute
Read speed: 560 characters/minute

NEC NEAC-2204 system (including the main unit, an I/O controller, a magnetic tape unit, a high-speed