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The IMSAI 8080


Floppy Disk Drive

The Floppy Disk Drive is recommended for high-speed, mass data storage. Each disk stores up to 243K bytes of data, with average access time of 330 milli­seconds.

The IMSAI Floppy Disk Drive is available in a desktop cabinet or in a rack-mount package. The drive is built on a rugged, compact casting, and uses positive pressurization and self-contained air filters to assure continued reliability. The read/write heads retract automatically to reduce wear.

The front panel of the drive contains a number of indicators, including READY and SELECTED. For the selected drive these indicate:


The head is at track zero.


Write operation is in progress.


Head is loaded on the disk.


Disk is physically write-enabled.

A phase-lock-loop data separator is provided in each cabinet for increased reliability. The IMSAI 8080 system per­mits you to connect up to four disk drives through a single interface, giving you a total mass storage capacity of more than one million bytes.

Floppy Disk Drive


Unformatted Capacity


Per flexible disk: 3.2 million bits/ 400K bytes


Per track: 4 1.7K bits/5K bytes 3740 Format Capacity


Per flexible disk: 1.9 mfflion bits/ 243K bytes


Per track: 26.6K bits/3.3K bytes


Per sector: 1024 bits/128 bytes

Transfer Rate: 250K bits per second (nominal)

Track Density: 48 tracks per inch (0.021-in, track width)

Positioning Times


Access: 6 ms track-to-track


Head Stabilization: 10 ms


Head Load: l6 ms


Motor Start to Ready: 2 smaximum

Rotational Speed: 360 rpm ± 2.4% (167 ms/rev.)

Positioning Mechanism: Stepping motor, electrical detent

Media: IBM 3740 Diskette or IMSAI­approved equivalent

Dimensions: Same as IMSAI 8080 computer



Read Error, soft: Less than 1 in 109 bits


Read Error, hard: Less than 1 in 1012 bits


Positioning Error: Less than 1 in 106 accesses


MTBF: Better than 5000 hr


MTTR: Less than 30 mm


Component Life: More than 10,000 hours on all components

Heat Dissipation: 275 BTU/hr

Dual Drive Cabinet FDC 2-1

This is a dual-drive cabinet containing one disk drive with power supply and phase-lock-loop. Order a CABLE C to connect it to the computer chassis or, if this is a second Floppy Disk Drive cabinet, to connect it to the first cabinet. Includes a floppy diskette.

Rack Mount Hardware FDC-RM

This is hardware permitting the disk drive cabinet to mount in a standard 19-inch electronics rack. It consists of side panels that bolt to the inside of the electronics cabinet and a special dust cover. Order the rack mount option only in conjunction with an FDC 2-1.

Floppy Disk Drive FDC

Disk drive and power supply to add a drive to the dual-drive cabinet FDC 2-1. Includes a cable to interconnect drives within the cabinet. Includes a floppy diskette.

Floppy Diskette FDD

The recording medium for the Floppy Disk Drive. Equivalent to IBM 3740 Diskette.

Floppy Disk Interlace FJF

The FIF board is an interface/controller consisting of an IFM (Interface Master Board) and a FIB (Floppy Disk Interface board) which interface the disk to the computer.

The combination of FIB and IFM boards creates an intelligent controller including DMA transfer, which permits the computer to perform other tasks during disk operations.

The IFM board uses its own 8080A processor which is programmed to sup­port the floppy disk system. The program is stored in 1K byte EPROM chips and can be changed to support different data formats and densities on the floppy disk drives. Included is a disk bootstrap capability that reads and executes the contents of the first disk sector, allowing the disk operating system to gain con­trol after turning on the computer.

A single FIF interface will control up to four disk drives in a daisy chain signal bus, and can write-protect drives under software control. Commands in­clude Read Clock and Data Bits, Write Sector, Read Sector, Verify Sector, For­mat Track, Write Deleted Data Sector Mark, Write Protect, Write Enable and Restore Drive.

Logical and physical track addresses may be different. Cyclic redundancy checks are performed automatically. When an error is detected in reading or writing, the logic automatically retries up to 10 times.

The FIF board is furnished with a CABLE A to connect the board to the rear of the computer chassis. Order CABLE C to connect the chassis to the Floppy Disk Drive cabinet.

Two edge connectors EXPM are required.

Disk Drives Disk-50, Disk-80, Disk-200

You can specify 3330-type disk drives with 50, 80 or 200-megabyte capacities. Each drive is supplied with Disk Drive Interface HDIF.

Please contact the factory for additional information.

Serial Printer PTR-30A

This serial printer produces letter-quality copy and will operate in the plot mode to produce graphs. Print fonts are changeable, and two-color ribbons are available.

The printer operates at a rate of 30 characters per second, using the Hy-Type I daisy-wheel printer mechanism. It will space up, down, right or left. Tabs are program-controlled and operate at high speed in either direction. The platen is 132 characters wide.

The printer includes a power supply. A software driver program listing is furnished with the printer to facilitate normal character printing and plotting. The driver routine uses about 512 bytes of memory.

The required interface is the PlO 4-1 with an installed Parallel I/O Module (PIOM) and two PlO cables.

A 10-foot round cable is furnished to interconnect the printer with three male 25-pin EIA-type connectors to the rear of the computer chassis.


Print Speed: 30 characters per second (average text)

Character Set: 96 characters 'Print Line: 132 columns Form Width: 15 inches maximum Carriage Return Time: 400 ms maximum for 132 columns Tabulation: Right and left, direct to column address

Tabulation Speed: 400 ms maximum for 132 columns

Column Spacing: 60 positions per inch (nominal)

Paper Feed: Bidirectional

Paper Feed Spacing: 48 positions per inch (nominal)

Paper Feed Speed: 4 inches per second plus 50 ms settling delay

Dimensions: 81/2 in. high, 22'/2 lfl. wide, 131/2 in. deep Weight: 30 lb

Tractor Feed Option PTR-30A-TF

This option for the PTR-30A printer pro­vides greater paper control when using multipart forms. It also provides better registration when backing-up a line and overprinting. Only available when ordered with PTR-30A.

Line Printer PTR-300A

The Line Printer prints up to 314 lines of 80-column material per minute. The unit is ruggedly built and produces a high-quality copy on standard fan-folded or rolled forms from 4 to 9 ¾ inches wide. Multipart forms may have up to six parts. Form width and length are operator-adjustable to permit the printer to handle a variety of forms.

The standard USASCII 63-character set is provided. Character spacing is 10 characters per inch and 6 lines per inch, operator-adjustable to 3 lines per inch.

The printer mechanism uses indi­vidual type pallets in an endless revolv­ing carrier belt. This system gives you high-speed operation along with the good character quality and changeability advantages of an impact typebox printer.

Automatic Character Substitution: The printer may be made to print either the upper-case equivalent of a received lower-case character, or the substitute character.

Parity Error Indication: The printer prints the substitute character for a character received with an even parity error. The printer is easily changed to operate with odd parity or none.

Test Character Generation: A switch inside the printer may be used to test the printer mechanism by printing a substitute character in all printable positions of consecutive lines.

The printer includes power supply and a 10-foot flat cable terminated by a 25-pin EIA-type connector which connects to the rear of the computer chassis. The required interface for the Line Printer is the Line Printer Interface board set (LIF).

Line Printer PTR-300B

This line printer is 132 columns wide and in all other respects equivalent to Line Printer PTR-300A. The maximum paper width is 14 ¼ inches. Requires interface board set LIF.

Line Printer Interface LJF

The LIF interfaces the Line Printer to the computer. It consists of an Interface Master (IFM) board and a Line Printer (LIB) board. The combination of LIB and IFM boards creates an intelligent controller including DMA transfer, per­mitting the computer to perform other tasks during printer operations.

The IFM board uses its own 8080A processor which is programmed to sup­port the printer. The program is stored in 1K byte PROM chips.

The LIF board is furnished with a CABLE A to connect the board to the rear of the computer chassis and a cable to connect the chassis to the Line Printer.

Requires two edge connectors EXPM.

Video Display/Keyboard Terminal CRT-2480A

The Video Terminal is a high-quality 24-line, 80-character-per-line terminal featuring:

12-inch (diagonal) CRT with P4 white phosphor and etched non-glare surface

59-key keyboard with office typewriter layout and containing all teletype­writer data and control keys

Displays 64 ASCII characters (upper­case, numeric and punctuation)

RS232C and current-loop interfaces at standard communications baud rates from 75 to 19,200 baud for full-duplex or half-duplex asynchronous operation

Automatic scrolling with new data entered at screen bottom

Variable communications format: word length, parity and stop bits switch-selectable.

The terminal includes a 3-foot round communications cable terminated by a male 25-pin EIA-type connector. The required interface is an SIO 2-2 or SIO 2-1 board.

To extend the length of the cable furnished, order CABLE C.

Terminal dimensions are: 13 ½ in. high, 15 ½ in. wide, 19 in. deep. It weighs 25 pounds and requires 80 Watts of 115V ac power.

Video Display/Keyboard Terminal CRT-1280A

This is identical to the CRT-2480A except that it provides 12 lines on the screen instead of 24 lines.

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