IBM 305 RAMAC
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![]() IBM 305 RAMAC system:
IBM 305 main system (Processing unit, magnetic process drum, magnetic core register, electronic logical and arithmetic circuits) | |
Developer | IBM |
---|---|
Manufacturer | IBM |
Release date | September 14, 1956 |
Introductory price | US$3,200(equivalent to $34,700 in 2023) per month |
Discontinued | 1961 |
Units sold | More than 1,000 |
Successor | IBM 1401 |
Website | www |
TheIBM 305 RAMACwas the first commercial computer that used a moving-headhard disk drive(magneticdisk storage) forsecondary storage.[1]The system was publicly announced on September 14, 1956,[2][3]with test units already installed at the U.S. Navy and at private corporations.[2]RAMAC stood for "Random Access Method of Accounting and Control",[4]as its design was motivated by the need for real-time accounting in business.[5]
History
[edit]RAMAC was developed and manufactured at IBM's research facility inSan Jose, California.In 1959, IBM's CEOThomas J. Watson Jr.exhibited the RAMAC inMoscow.This led to a visit by Soviet leaderNikita Khrushchevto IBM's San Jose facility.[6]
The first RAMAC to be used in the U.S. auto industry was installed atChrysler'sMOPARDivision in 1957. It replaced a hugetub filewhich was part of MOPAR's parts inventory control and order processing system.
During the1960 Olympic Winter GamesinSquaw Valley(USA), IBM provided the first electronic data processing systems for the Games. The system featured an IBM RAMAC 305 computer, punched card data collection, and a central printing facility.
More than 1,000 systems were built. Production ended in 1961; the RAMAC computer became obsolete in 1962 when theIBM 1405Disk Storage Unit for theIBM 1401was introduced, and the 305 was withdrawn in 1969.
Overview
[edit]The first hard disk unit was shipped September 13, 1956.[7]The additional components of the computer were a card punch, a central processing unit, a power supply unit, an operator's console/card reader unit, and a printer. There was also a manual inquiry station that allowed direct access to stored records. IBM touted the system as being able to store the equivalent of 64,000punched cards.[5]
The 305 was one of the lastvacuum tubecomputers that IBM built. It weighed over a ton.[8]
TheIBM 350disk system stored 5 millionAlpha numericcharacters recorded as six data bits, oneparity bitand one space bit for eight bits recorded per character.[9]It had fifty 24-inch-diameter (610 mm) disks. Two independent access arms moved up and down to select a disk, and in and out to select a recording track, all underservocontrol. Average time to locate a single record was 600 milliseconds. Several improved models were added in the 1950s. The IBM RAMAC 305 system with 350 disk storage leased for US$3,200 (equivalent to $34,700 in 2023) per month.
![](https://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/BRL61-IBM_305_RAMAC.jpeg/220px-BRL61-IBM_305_RAMAC.jpeg)
The original 305 RAMAC computer system could be housed in a room of about 9 m (30 ft) by 15 m (50 ft); the 350 disk storage unit measured around 1.5 square meters (16 sq ft). Currie Munce, research vice president forHitachi Global Storage Technologies(which has acquired IBM's hard disk drive business), stated in aWall Street Journalinterview[10]that the RAMAC unit weighed over a ton, had to be moved around with forklifts, and was delivered via large cargo airplanes. According to Munce, the storage capacity of the drive could have been increased beyond five megabytes, but IBM's marketing department at that time was against a larger capacity drive, because they did not know how to sell a product with more storage.
![](https://upload.wikimedia.org/wikipedia/commons/thumb/b/b4/IBM_350_RAMAC.jpg/220px-IBM_350_RAMAC.jpg)
Programming the 305 involved not only writingmachine languageinstructions to be stored on thedrum memory,but also almost every unit in the system (including the computer itself) could be programmed by inserting wire jumpers into aplugboardcontrol panel.
Architecture
[edit]This sectionneeds additional citations forverification.(September 2013) |
System architecture was documented in the305 RAMAC Manual of Operation.[4] The 305 was a character-orientedvariable "word" lengthdecimal (BCD) computer with adrum memoryrotating at 6000RPMthat held 3200Alpha numericcharacters. Acore memorybuffer of 100 characters was used for temporary storage during data transfers.
Each character was six bits – plus oneodd paritybit ( "R" ) – composed of two zone bits ( "X" and "O" ) and remaining four binary bits for the value of the digit in the following format:
X O 8 4 2 1 R
Instructionscould only be stored on 20 tracks of the drum memory and were fixed length (10 characters), in the following format:
- T1A1B1T2A2B2M N P Q
Field positions | Function |
---|---|
T1A1B1 | Source operand address – Track, low order AB character |
T2A2B2 | Destination operand address – Track, low order AB character |
M N | Length of operands (each operand must be entirely on its specified track) |
P | Program exit code; used to select test conditions, perform jumps, and initiate input/output. The 305's control panel programming determines the action(s) performed. |
Q | Control code; modifies the operation (similar to anop code), the default operation being a copy from source to destination. Other operations were: "1" Compare, "2" Field compare, "3" Compare & Field compare, "5" Accumulator reset, "6" Blank transfer test, "7" Compress & Expand, "8" Expand, "9" Compress |
Fixed-pointdata "words" could be any size from one decimal digit up to 100 decimal digits, with the X bit of the least significant digit storing the sign (signed magnitude).
Data records could be any size from one character up to 100 characters.
Drum memory
[edit]The drum memory was organized into 32 tracks of 100 characters each.
The color code of this table is:
- Yellow – Storage
- Blue – Arithmetic
- Green – Input/output
- Red – Special function
Track specifier | Source function | Destination function |
---|---|---|
W X Y Z | General storage | |
0 1 2 3 4 5 6 7 8 9 & A B C D E F G H I |
Instruction storage, general storage | |
L | Read accumulator | Add to accumulator |
M | Read & clear accumulator | Subtract from accumulator |
V | Multiplicand (1 to 9 characters) or divisor (1 to 9 characters) | |
N | — | Multiply (1 to 11 characters) Stores 2 to 20 character product in accumulators 0 & 1 |
P | — | Divide (option) |
K | 380 Punched card input | — |
S T | — | 323 Punched card output, 370 Printer Output, 407 Printer output |
Q | 380 Inquiry input/output | |
J | — | 350 File Address |
R | 350 File data input/output | |
- | Core buffer | Character selector |
$ | 382 Paper tape input/output (option) |
L
andM
select the same track, containing ten 10-character "Accumulators".As a destinationLspecifies addition,Mspecifies subtraction. (Numbers in these accumulators were stored inten's complementform, with the X bit of the most significant digit storing the sign. The sign of each accumulator was also held in arelay.However the 305 automatically converted between its standard signed magnitude format and this format without the need for special programming.)
J
,R
,and-
do not select tracks on the drum, they specify other sources and destinations.
Jumps
[edit]The 305's instruction set does not include any jumps, instead these are programmed on the control panel:
- Unconditional jump – the program exit code (P field) specifies aProgram exit hubon the control panel, which has a wire plugged into it and, via distributors, toProgram entry hubsspecifying the first, second and third address digit of the instruction to jump to.
- Conditional jump – the program exit code (P field) specifies aProgram exit hubon the control panel, which has a wire plugged into it and the appropriateCondition selector common hubto be tested, the corresponding twoCondition selector output hubs have wires plugged into them and theProgram entry hubs specifying the instructions to jump to or theProgram advance hubto continue in sequence. Complicated conditions involving manyCondition selectorscould be wired to execute in a single instruction (e.g., Testing the sign and zero states of multiple accumulators), with one of severalProgram entry hubs activated.
- Multi-way jump – the destination track (T2field) is set to
-
and the appropriateCharacter selector hubs on the control panel have wires plugged into them and theProgram entry hubs specifying the instructions to jump to or theProgram advance hubto continue in sequence.
Timing
[edit]All timing signals for the 305 were derived from a factory recordedclock trackon the drum. The clock track contained 816 pulses 12 μs apart with a 208 μs gap for sync.
Reading or writing a character took 96 μs.
The 305's typical instruction took three revolutions of the drum (30 ms): one (I phase) to fetch the instruction, one (R phase) to read the source operand and copy it to the core buffer, and one (W phase) to write the destination operand from the core buffer. If the P field (Program exit code) was not blank, then two (D phaseandP phase) additional revolutions of the drum (20 ms) were added to the execution time to allow relays to be picked. TheImproved Processing Speedoption could be installed that allowed the three instruction phases (IRW) to immediately follow each other instead of waiting for the next revolution to start; with this option and well optimized code and operand placement a typical instruction could execute in as little as one revolution of the drum (10 ms).
Certain instructions though took far longer than the typical 30 ms to 50 ms. For example, multiply took six to nineteen revolutions of the drum (60 ms to 190 ms) and divide (an option) took ten to thirty seven revolutions of the drum (100 ms to 370 ms). Input/Output instructions could interlock the processor for as many revolutions of the drum as needed by the hardware.
Hardware implementation
[edit]The logic circuitry of the 305 was built of one- and two-tube pluggable units and relays.
Related peripheral units
[edit]![](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c3/IBM_305_RAMAC_system_%282%29.jpg/220px-IBM_305_RAMAC_system_%282%29.jpg)
![](https://upload.wikimedia.org/wikipedia/commons/thumb/f/f3/IBM_380_console_%281%29.jpg/220px-IBM_380_console_%281%29.jpg)
A basic system was composed of the following units:
- IBM 305 – Processing unit, the magnetic process drum, magnetic core register and electronic logical and arithmetic circuits
- IBM 350– Disk storage unit
- IBM 370– Printer
- IBM 323 – Card punch
- IBM 380 – Console, the card reader andIBM Electric typewritermodel B1
- IBM 340 – Power supply
See also
[edit]References
[edit]- ^Preimesberger, Chris (2006-09-08)."IBM Builds on 50 Years of Spinning Disk Storage".eWeek.Retrieved2012-10-16.
- ^ab650 RAMAC announcementThe 305 RAMAC and the 650 RAMAC were internally announced on September 4, 1956.
- ^I.B.M. To Put Out New 'Think' Units,New York Times,September 14, 1956
- ^ab305 RAMAC Manual of Operation,IBM, April 1957.
- ^abIBM RAMAC promotional film
- ^McElvenny, Ralph; Wortman, Marc.The Greatest Capitalist Who Ever Lived.p. 276.ISBN978-1-5417-6852-9.
- ^Steven Levy, "The Hard Disk That Changed the World"Newsweek,August 7, 2006
- ^Weik, Martin H. (March 1961)."IBM 305 RAMAC".ed-thelen.org.A Third Survey of Domestic Electronic Digital Computing Systems. SeeSUNOCO Philadelphia.
- ^"RAMAC 305 Customer Engineering Manual of Instruction"(PDF).IBM Corp., 1959.pp. 7–8 and 85.
- ^Lee Gomes, "Talking Tech"The Wall Street Journal,August 22, 2006
External links
[edit]![](https://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
- IBM 305 RAMAC Data Processing System
- IBM Archives on the 305
- IBM 350 RAMACsite originally prepared under the supervision of the Storage Special Interest Group of theComputer History Museum
- Youtube video