What is the IBM 5110, and why is it so special?
First we must discuss the predecessor; in 1975, IBM released the 5100, one of the first commercially supported microcomputers priced effectively and targeting engineers, analysts, statisticians, and other problem-solvers, mainly in educational or engineering settings. Based on a proof-of-concept system called SCAMP, for "Special Computer, APL Machine Portable", the 5100 was IBM's first commercially available and supported "personal" portable computer. The system was a self-contained computer that could transport easily. It featured onboard storage of 204K via the tape drive, up to 64K of memory (R/W Storage), a full-featured keyboard with a numeric pad for quick keying of data, and a built-in 5" screen.
The difference is the terminology changed from the 1970s to the 1980s as technology advanced. The term microprocessor was used to mean "a processor that executes microcode in order to interpret a higher-level instruction set". Official usage changed to refer to it as a processor, "implemented on a single monolithic integrated circuit." To summarize, the computer is unique because it contains a board-level processor. Not on a single die, but made up of logic on different physical boards. The system sparked the beginning of IBM's entrance into the personal computer market, years before any x86 based computer would assume that title.
Successor to the 5100
Jump forward three years to 1978 when IBM released the 5110, with the idea to market more microcomputers to small and medium-sized businesses. As BASIC was becoming the choice language for computing, IBM added the disk storage option and released a catalog of programs. Options like General Ledger, Payroll, Accounts Payable and Receivable, and Inventory and other titles targeting different business data processing needs like word processing and financial data processing programs.
With the newer model, more I/O options were available like the choice of either/or the Diskette Unit and tape storage, different printer options, choice of Programming Language, a communications interface, and even serial and parallel options for special purpose attachments. There were also authorized third-party options, including a 10MB hard disk drive and network adaptors.
2 Models are displayed from a sales ad for the 5110. (Background) the Model 1 with the External Tape Unit (5106), both APL and BASIC. (Foreground) the Model 2, with 2 Disk Units (5114) and the Printer (5103).
The Disk System offered users more options for storage and advanced applications. Operators can attach one or two diskette units to the 5110—each diskette unit featuring one or two diskette drives. The expanded disk I/O provides operators with a total online diskette storage capacity of 1.2 million to 4.8 million bytes, massive for the time this machine came out.
The 5110 with Tape, Disk Unit, and Printer. The processor shown appears to support both APL and BASIC with both the Tape and Disk System.
The drives are Double Sided-Double-Density drives, referred to as IBM Type 53FD. Diskette Type 2D and the 53FD diskette drives provided new diskette capacity and performance to IBM systems and permitted users to further optimize or extend their systems. The IBM 5110 enhanced applications with dual diskette drives that provide an economical processing Direct Access Storage Device (DASD) file capability and the exchange medium function of the diskette.
This particular system (Model 2) shipped with no APL; it has two 16K R/W storage cards giving it 32K of memory. It did not ship with the tape unit or the hardware installed to run the external tape drive (5106). This setup targeted businesses that needed programs for word processing, databases, and financial applications.
The keys on the keyboard are in a typewriter-like arrangement. The keyboard also contains a cluster of 10 numeric keys and calculator functions arranged like a standard adding machine.
The 5110 keyword and command keys are easily identified along the top row of the keyboard. You can request specific system functions and enter character combinations with a single keystroke using the keyword and command key combinations. Just above the keyboard are specific routine BASIC functions like RUN and LOAD. Operators can use the CMD + desired FN key instead of typing out the entire word when programming.
The Front Panel features switches for controlling the screen's brightness and a special L32 64 R32 rocking 3-way switch. This switch changes the screen to a 32 column mode that spaces out the displays left or right 32 columns.
The other switches on the front allow the operator to reverse the display, only affecting the internal display. Reversing the display was helpful for some who preferred the viewing option for comfort. It made the text black on a white background.
The Disk Unit is the biggest part of the system; the diskette unit features two eight-inch double-sided, double-density diskette drives. The diskette system for the 5110 allowed operators to exchange data with other computer systems, such as the IBM 3741 Data Station, IBM System/32, IBM 3031/3032 processor, and the IBM System/34.
"The capability to exchange data with other systems helped operators to adapt the 5110 to growing data processing needs. For example, data recorded by a 3741 could be read from the diskette and processed by the 5110 while the 3741 operator recorded more data on another diskette."
The diskette used to exchange data between the 5110 and another system had to be IBM-compatible diskette types 1, 2, or 2D. The data was recorded in the 128-byte basic exchange or 256-byte H-type exchange formats.
The most intriguing and daunting part about this drive system is that it is 100% IBM Proprietary. From the cards that control the diskette unit to the cards that control the floppy drives, it's all documented highly detailed in the service guides but not like any common drive systems. With most other computers of the 80s, manufacturers followed standards. This system contains the IBM 53FD floppy disk units, made a few iterations before more modern standards that made the later 5.25" mini-diskette.
Power is passed through the cable that runs from the main processor to the disk units, tape, and printer, but the disk units contain power supplies for the disk drives. The internal PSU delivers +5/-5v and +24v for the diskette drives and AC for the cooling fan at the top.
The drive systems are seemingly complex, with detailed schematics and test points on all aspects of the Disk Unit. The disk drives can be individually troubleshot, serviced, and repaired using the documentation that comes with, eventually we will take this road.
The 5103 Printer shipped in two models, Model 11 has a speed of 80 characters per second (cps), and Model 12 has a rate of 120 characters per second. We will need to reference which model we have.
The 5103 Printer is capable of printing uppercase and lowercase characters, numeric characters, and special symbols. The head prints in both directions, thus reducing print time and features a print overlap capability; that is, certain calculations and output printing can occur simultaneously.
For example, the 5110 can be calculating an extended price (unit price times quantity) while the printer is printing the previous calculation results. This overlap of functions can increase the speed with which the system completes a job.
The documentation states that if you need a group of people to view the same information on the display screen, you can attach up to six black-and-white TV monitors to the 5110. The composite output allows the information on the internal display screen to be viewed on additional screens. You might see this in a financial office where data needs to be seen during processing by multiple teams.
Included is a LEEDEX Corporation Video 100 monochrome monitor. The look and feel of this monitor, similar to the TRS-80 computer experience, more than any others.
The Cover Removed
The first brave step in getting work completed with the machine is opening it up, and opening the system does not disappoint. There is serious intrigue in the technology, not because it is ancient but almost foreign to the computers we know today.
Opening the case reveals the A1 board, upside down in the operating position. The motherboard, referenced as the A1 board, is not a Printed Circuit Board (PCB); the wiring is done either by hand or machine-assisted hands. The board acts as an insulator, and each pin is connected by wire.
All of the A1 boards throughout the processor and the disk system are wired this way. There is likely some form of it in the printer, but we haven't opened it up yet for maintenance.
Notice the numbers and letters that run the perimeter of the board? These are used in troubleshooting and, combined with documentation, guide technicians to the troubled part. The documentation supports a heavily formatted framework for troubleshooting the machine, including schematics, Maintenance Analysis Procedures (MAPs), and other supporting processes for diagnosing and repairing the entire system.
Dust, Dirt and Rotted Foam
Inside the machine, generally above the keyboard electronics but under the keys and the main cards of the system at the base, is a foam that has broken down over time. This foam supports the main A1 board and feature cards and provides insulation to the keyboard mechanisms. The foam parts have broken down into either fine dust and circulated through the machine, or what was touching the glue used to hold it to the sticky backing turned it into a tar-like substance.
You could describe the consistency as really moist cake, and as you can see by the photos, it breaks apart very easily. As you touch and try to manipulate it, the material turns to tar and becomes even more challenging to remove.
Glues and sticky substances used back then break down over time; most manufacturers did not expect and therefore calculate this into production costs. After a certain period, wild things happen that weren't planned on.
The material needs to be removed while the system is working and before it causes any significant problems.
As previously stated, and if not, the electronics in this computer as of this writing are 42 years old. Getting the dirt and any contamination away becomes a priority at this point. Using a gentle hand and taking time, we removed the bad foam. Luckily the material was initially held in place by a thin sheet of plastic-backing, making removal relatively clean.
Keyboard Contamination
The next major hurdle to overcome was the stuck key issue. The system for intended purposes has been without issue. The BASIC games and other software titles provided with the machine worked great until we decided to make its first appearance in public.
During its debut with a local computer group meetup, it began acting up. The Video 100 monitor lost its vertical hold, the material in the keyboard started causing the keys to stick, which in turn caused the system to halt. The problems combined made a terrible first impression of the system, and most visitors lost attention quickly.
With the keyboard finally removed, an accurate picture of the damage can be seen. Each of the key posts pierced a protective sheet called the contamination shield. The material is so fragile it breaks up like the paper of a 4000-year-old scroll. As each part broke into smaller pieces and the keyboard was used, they started making their way down the access holes in the key module or down the middle.
After separating the assembly, multiple keys were found to have dislodged flyplates, and a few more might have been knocked loose during removal. The key modules snap into place from below the keyboard frame. All were put back together and lightly cleaned using mild detergent and water.
With all of the key modules in good shape, attention turns to the keyboard frame. Previously the frame contained a similar foam material that isolated the key modules from the frame and likely prevented mechanical interference when neighboring keys were depressed. Since the flyplates rest on the electronic pads of the keyboard, the slightest movement or resonance might cause unwanted keystrokes. The new material was applied to the keyboard frame using a soldering iron to make the holes and 15mm thick foam adhesive, and all keys were reinstalled, completing the keyboard.
The computer system is reassembled with the keys cleaned, the bad foam removed, the key flyplates fixed, and the machine blown out. One last undocumented step was to carefully remove the "smoked" plastic viewer that protected the CRT for cleaning. With the processor powered up, we performed a keyboard test to ensure all typewriter keys were working. So far, there have been no issues with the keyboard, and the system is much friendlier to use now.