IBM 5406 System/3

On March 4, 2021 the Arlington (Massachusetts) Coal & Lumber Company donated an IBM 5406 Model B3 System/3, S/N 32379, including a 5444 Model 1 disk drive, S/N 48754, and a 5213 Model 2 printer, S/N 21627, and equipped with 12k bytes of core memory . This system was installed on Valentine's day in 1973 and was used to manage their inventory and billing.

The System/3 is the first member of IBM's Midrange Systems that were produced in Rochester Minnesota from July 30, 1969 to June 1985. The 5406 was introduced on October 28, 1970.

There is a WWW site dedicated to the IBM System/3 here: http://www.ibmsystem3.nl/overview.html There are 42 System/3 machines known to exist.

Quite a bit of documentation for this machine has been scanned and is available here.

IBM 5406 System/3 Restoration blog.

This list describes all of the features that were included when the machine was first built.

The disk drive in the original order is a 5444 Model 1 with a 1.2MB fixed and 1.2MB removable storage. The disk controller is actually jumpered for a 5444 Model 2 with 2.4MB fixed and 2.4MB removable storage. Sometime in the machine's working life the disk capacity was upgraded. The 5444 Model 1 and Model 2 drives are physically the same, but the Model 1 is restricted to 1/2 of the full capacity.

Optional Features that are not installed on this machine:

  • Bisynchronous Communications Adapter: Allows this system to talk to a mainframe through a modem. BISYNC allows you to transfer files and reports between the two machines, as well as run jobs on the other machine.

  • Serial I/O Channel:

  • 2222 Wire Matrix Printer and and Ledger Card Device:

  • 2265-2 Display Unit: It sits on the desk to the left of the printer. The 2265-2 can be used for output for interactive work instead of the 5213 printer.

  • 5444 Model 2 or Model 3 disk: A second disk could be added in the lower drawer at the left of the desk.

  • 5496 Data Recorder:

The system was ordered with a 5444 Model 1 disk drive, S/N 48754, that has one 1.2MB fixed disk and one 1.2MB removable disk. Sometime during it's working life the storage was upgraded from a Model 1 to a Model 2. This increased the storage to 2.4MB fixed disk and one 2.4MB removable Typically the operating system and application programs were on the fixed disk, and customer data files were on the removable disk. The first 5444 disk drive is located in the top drawer at the left of the desk, and the lower drawer is empty. A second 5444 disk drive could be installed in the lower drawer. A 5444 Model 2 drive was also available with twice the storage.

This system does not have the optional 2265-2 Display Unit so commands are entered on this keyboard and the results are shown on the printer.

This is the 5444 disk drive without the removable disk pack installed. There is a fixed disk platter inside the drive.

It looks like the 5444-1 drive that we have is restricted from accessing the remaining 100 cylinders that exist on the drive. We are investigating how the cylinder restriction is implemented in the disk controller.

The labels on the drive show that it is a 5444 Model 1, S/N 48754. This drive has 104 tracks per surface, 100 for data, 3 alternate tracks used to replace defective tracks (1,2,&3) and a CE track (103). Sector 0 , Track 0, Head 0, on both the fixed and removable platters contain boot blocks. With two surfaces per drive it yields 200 tracks on the fixed and 200 tracks on the removable parts of the drive. Each track has 24 256 byte sectors. That yields 1.2MB of storage for the fixed and 1.2MB for the removable parts of the drive. The average access time for the drive is 153 ms, about 7 times slower than a modern laptop drive. The 5444-2 drive has double the capacity of the 5444-1 drive.

The 5444 drive shown with the removable disk pack and it's cover installed.

This is the 5213 Model 2 printer with the cover open. It can print 132 columns of text at 6 lines per inch. It only prints in one direction, at a rate of 8.5 inches per second. The newer Model 3 printer can print in both directions. The ink ribbon mechanism has problems detailed below.

The front of the processing unit holds the Customer Engineer (CE) Panel. This is used to diagnose and repair the machine. The CE Panel can be lifted and places on the top of the cabinet to provide better access when the right side is open. A cassette tape deck can be connected to the CE panel to load disk diagnostics when the disk is broken.

The is the back of the CE panel. You can see the labels on the back of the roller for the faults and the rotary switch that lets the system know what position the roller is in. The shielded gray cable is use for the logic probe and the cassette tape player.

The double doors on the right of the processing unit open to reveal five populated card cages. The bottom right card cage is not installed, and likely is used for a controller option that is not installed on this machine. The bottom left card cage holds the 12k of core memory.

The frame swings out to allow access to the SLT modules. The back of the monstrous power supply is at the left.

This is the label on the side of the swing out processor unit frame. It looks like signal names and locations on the pins on the backplanes.

This is the inside of the processor unit frame. There are normally covers over the Monolithic System Technology (MST) logic cards to allow for good air flow, but I removed them so you could see the cards. The chassis at the bottom right holds 12k of core memory. There should be "X" shaped rubber parts holding the ribbon cables into the channels. All but one at the left have deteriorated and fallen off.

Looks like the Core memory is OK.

The back of the processing unit holds additional electronics. We will open this part and post images soon.

With the sheet metal cover removed you can see the heat sinks for the +6V, -4V, and -30V power supplies. The air filters below the heat sinks look like they have never been changed since the system was installed. The IBM CEs should have replaced them as part of the periodic maintenance.

The sheet metal covers that are normally installed on the left side of the processing unit were left behind when the machine was picked up. The silver boxes contain the power control devices. The cables in this area are normally connected to the keyboard, printer, and disk drive in the desk. There are two hour meters at the right. The upper one logs customer on time, and the lower one logs Customer Engineer (CE) on time. IBM would lease machines based on the time used. The CEs had a separate hour meter so the customer did not pay for repair time. There is a third hour meter at the top left for the disk drive.

This is the power connector for the whole system. The connector is made by Russell and Stoll (now part of Thomas and Betts). It is part number 3913 and the mating receptacle is part number 3743. I ordered a new-old-stock receptacle from eBay. This connector means that the system is wired for 208/230VAC single-phase and needs a 20A circuit.


When the disk or disk controller fails, you can load diagnostic programs from a cassette player connected to the CE panel. You need to have a special board installed in the CPU cabinet to use the cassette player. We need to determine if the special board is installed in our machine.

We have the Customer Engineer disk pack for this system. This is installed in the removable part of the disk drive, and boots a tiny operating system. You can then load diagnostics for any part of the system. Since this machine has core memory, you can power off the machine and the diagnostic will stay in memory.

Quite a bit of CE microfiche came with the machine. If a PDF file of the microfiche is available, it is a clickable link.

  • 5129401, 00D1_2, CPU Test 1, 5-Jun-70

  • 5129403, 00D2_2, Loader For CPU Test, 5-Jun-70

  • 5129405, 00D3_0, CPU Test 3, 20-Dec-69

  • 5129407, 00D4_1, CPU Test 4, 10-Apr-70

  • 5129409, 00D5_1, CPU Test 5, 10-Apr-70

  • 5129411, 00D6_1, CPU Test 6, 10-Apr-70

  • 5129413, 00D7-1, CPU Test 7, 10-Apr-70

  • 5129415, 00D8_0, CPU Test 9, 20-Dec-69

  • 5129417, 00D9_0, CPU Tests A, C, E, 20-Dec-69

  • 5129419, 00DA_0, CPU Test F-10, 20-Dec-69

  • 5129421, 00DB_0, CPU Tests 11-14, 20-Dec-69

  • 5129423, 00DC_0, CPU Tests 15-17, 20-Dec-69

  • 5129425, 00DD_0, CPU Tests 18-19, 20-Dec-69

  • 5129427, 00DE_0, CPU Tests 1A, 1C, 1F, 20-Dec-69

  • 5129429, 00DF_0, CPU Tests 20-22, 20-Dec-69

  • 5129431, 00E1_0, CPU Tests 24-26, 20-Dec-69

  • 5129433, 00E2_0, CPU Tests 27-29, 20-Dec-69

  • 5129435, 00E3_0, CPU Tests 2A, 2C, 2E, 20-Dec-69

  • 5129437, 00E4_0, CPU Tests 2F, 30, 20-Dec-69

  • 5129439, 00E5_0, CPU Tests 31-33, 20-Dec-69

  • 5129441, 00E6_0, CPU Tests 34-36, 20-Dec-69

  • 5129443, 00E7_2, CPU Tests 37-39, 14-Sep-70

  • 5129445, 00E8_2, CPU Tests 3C, 3E, 5-Jun-70

  • 5129447, 00E9_0, CPU Tests 3F-42, 20-Dec-69

  • 5129449, 00EA_1, CPU Tests 68, 69, 6A, 6C, 60, 5-Jun-70

  • 5129451, 00EB_1, CPU Tests 6E, 6F, 7A, 7C, 5-Jun-70

  • 5129453, 00EC_0, CPU Tests 70-73, 20-Dec-69

  • 5129455, 00ED_0, CPU Tests 83-86, 20-Dec-69

  • 5129457, 00EE_0, CPU Tests 8P, 91, 20-Dec-69

  • 5129459, 00F5_0, CPU Test 93, 20-Dec-69

  • 5129658, 00F5_3, C.E Disk Initializer, 1-Oct-70

  • 5129461, 00F6_1, CPU Test 94

  • 5129463, 00F7_1, CPU Test 95, 10-Apr-70

  • 5129465, 00F8_1, CPU Test 96, 10-Apr-70

  • 5129467, 00F9_1, CPU Test 97, 10-Apr-70

  • 5129469, 00FA_0, CPU Tests A0-A1, 20-Dec-69

  • 5129474, 0121_6, Keyboard Adapter Function Test, 30-Jun-72

  • 5129664, 012F_0, System Test Keyboard Module, 10-Apr-70

  • 5129690, 0381_1, Tape Loader Checkout, 15-Jan-72

  • 5129480, 0901_2, CRT Diagnostic, 11-May-70

  • 5129670, 090F_0, System Test CRT Module, 10-Apr-70

  • 5129611, 0A01_4, File Control Unit Fault Section 1, 1-Mar-71

  • 5129624, 0A03_6, Seek Function Test, 15-Mar-72

  • 5129628, 0A05_6, Disk Write Function, 21-Apr-72

  • 5129630, 0A06_3, Verify Data Function Test, 1-Aug-70

  • 5129632, 0A07_2, Read Diagnostic Function Test, 1-Aug-70

  • 5129634, 0A08_3, Read Data Function Test, 1-Oct-70