A Tribute to the Dick Smith System 80
(aka Video Genie and PMC-80/81)

Common System 80 Expansion Options


The System 80 came with a number of expansion options. A suite of standard accessories were produced by EACA and sold via Dick Smith Electronics Ltd. A few third-party goodies were also popular expansion options.

1.0 Dick Smith Expansion Options
  1.1 Expansion Unit
  1.2 Disk Drives
  1.3 Printer Interface and printers
  1.4 Dick Smith Green Screen Monitor
  1.5 "Sound Off" software synthesizer
2.0 Third-party Expansion Options
  2.1 Micro-80 Syspand Unit
  2.2 Micro-80 Expansion Unit
  2.3 System-80 Bus to TRS-80 Peripheral Cable
3.0 Third-party TRS-80 Accessories popular amongst System 80 owners
  3.1 Exatron Stringy Floppy
  3.2 Disk-80 Micromint Expansion Unit


1.0 Dick Smith Expansion Options

As with the TRS-80 Model 1, a set of "standard" expansion devices were available to System 80 owners wishing to "grow" their computers beyond the basic unit. These expansion options were not cheap, in many cases being as much as the initial outlay of the computer itself! 

1.1 Expansion unit

Expansion UnitThe Expansion unit was essentially a reasonably large non-descript rectangular box which, like the TRS-80 one, sat at the back of the main unit and beneath the monitor. It was cream coloured, to match the decor of the System 80 itself.  The expansion edge had a 50 pins on both the main unit and expansion unit, rather than the 40 found with the TRS-80 model 1. Like the TRS-80, peripherals were connected by ribbon cables.

There were two versions of the expansion unit released.  The original version (X4010) had a three-slot S100 bus backplane.  The main board, in the top slot, had a floppy disk controller, I/O mapped printer interface and RS-232 serial interface. An extra 16 or 32 KB of RAM was normally included in the form of a s100 memory card.  Both the parallel port, and RS 232 were configured to use the I/O port addresses rather than the memory addresses as explained elsewhere on this site. This meant TRS-80 software using these devices often required patching to work.  Alternatively, a simple hardware modification (detailed in the technical manual) could be done which made the printer interface available as a memory mapped device, like the TRS80 Model I, using a switch.  The default disk controller was single density but a Percom doubler card was stocked by Dick Smith Electronics Ltd, and could be (and often was) added through a simple hardware modification.

The later version (X4020) came out at the same time as the Blue-label model System 80. This was completely different. The S100 bus was gone, along with the serial interface. The Printer interface was also now memory mapped as well as I/O mapped and no switch was required. The 32KB memory expansion was now on the main expansion unit board, and there was a small slot for the serial interface to be installed. Assuming a doubler card was available, double density could be accomodated simply by plugging in the card and moving a few jumpers (see a picture of a double-density card here). The S100 interface was available as a separate add-on.  User and technical manuals for the X4020 can be downloaded here and a picture of the X4020 board can be seen here.

1.2 Disk Drives

System 80 Disk DriveThe standard disk configuration was one or two Percom, Pertek or MPI 40 track drives, again offered in a cream colour to match the decor (click here for a Dick Smith information sheet). The power supplies were built into the drives.  It came with a small A5 installation guide.

The DOS package sold with the System 80 disk option was one by Percom called OS-80 (which was actually Percom's TRS-80 MicroDos). It was inexpensive, and ok for a beginners DOS, but had no file handling routines or directory track. Most people soon dumped it for the more powerful TRS-80 DOS packages on the market at that time. 

A technical manual for the MPI drives can be found here.

1.3 Printer interface and printers

Dick Smith Electronics Ltd also sold a simple printer interface for those who simply wanted to be able to use a printer from a cassette based system. The interface was a large card-like device, one end of which plugged into the System 80 expansion bus, whilst the other end plugged into centronics compatible printer such as the monster Itoh 8300P.

Another printer which appeared later on the scene was the Dick Smith X3252.

1.4 Dick Smith Green Screen Monitor

Dick Smith Green ScreenThe System 80 could be plugged into a television but for some extra bucks Dick Smith was more than happy to provide a badged monitor too (Cat. X-1198). Essentially a small 12 inch television (of Asian origin) with the TV tuner removed, and composite and sound input jacks added. The light cream and black case suited the System 80 perfectly and many a unit was graced with these matching VDUs.

No manuals or circuit diagrams seem to exist on the web for this monitor but a schematic of the power supply (drawn by Philip Avery) can be found here.

1.5 Sound Off sound synthesizer

This gave the System 80 a voice and to allow rudimentary sound effects. Certainly software was supplied but in reading the manual I'm still not clear if users receive a small amplifier or were expected to find one? If anyone reading this could confirm one way or another I'd appreciate it.

 

Setting up an expanded System 80, with it's numerous cables and cards could be a daunting task to the uninitiated!  Bear in mind computers were not mainstream at this time.  Realising this, Dick Smith produced this handy assembly guide.

There may have been other standard expansion options offered through Dick Smith Electronics Ltd at the time. If anyone knows of any, please .


2.0 Third-party Expansion Options

Although many would dream about it, expansion through the Dick Smith route was often beyond the average System 80 owner. Given this situation, many users looked for more compatible, novel and/or less expensive gear. A small number of third-party firms built, or marketed products to hang off the 50 pin System 80 Expansion bus. Chief amongst these was Micro-80 products, a business associated with the popular Australian '80 support magazine. Among the products listed below, they also provided memory expansion and lower case upgrade kits.

2.1 Micro-80 Syspand Unit

Syspan 80Finished in a false wood grain and cream metal casing to match the decor, the Syspand 80 was a small self contained-cabinet (about 1/4 the size of an expansion unit) that plugged into the 50 pin port of the System 80. It offered a FULL TRS-80 Model 1 40 way bus as well as a centronics parallel printer port. This was great for folk who wished to plug in TRS-80 compatible expansion interface(s) and other goodies designed for the TRS-80 Model 1.

The printer port still used the standard System 80 I/0 port calls rather than the TRS-80 memory mapping so, like the printer port in the expansion interface, program patching was still often required.

The Syspand unit had it's own power supply, which added to the spaghetti jungle of cables that disk-capable machines usually found themselves coping with.  The manual is included on this site.

2.2 Micro-80 Expansion Unit

In 1984 Micro-80 offered their own System 80 expansion unit, followed soon by an integrated unit with disk drives included (called the '80 XT expansion). I'm not sure how many of these sold. The System 80 was getting long in the tooth by this stage and had been well-eclipsed by the C64 in the home market and PC's in the business world.

2.3 System-80 Bus to TRS-80 Peripheral Cable

Can't get a Syspand Unit and want to connect TRS-80 Model 1 hardware? How about a simple cable? Here is the pin assignment. This piece of hardware was originally designed to interface a System 80 with a TRS-80 Model 1 compatible disk controller and printer port expansion box called a DP1000. According to Knut Roll-Lund (a hardware wizard with these machines), this cable should be ok to be used with the TRS-80 Expansion Interface too PROVIDING you are not expecting it to carry RAM expansion signals as well. Then there might be a problem. However most System 80s had RAM expanded internally and if this is the case it shouldn't be an issue.

Like the Syspand unit, for a printer to work from a TRS-80 Model 1 expansion box with this cable, the printer code or hardware itself may need patching. My Stringy Floppy unit works with it well, so it may be ok for many of those TRS-80 Model peripherals that were designed to plug into the expansion port.


3.0 Popular TRS-80 Accessories

With a Syspand unit, or by wiring a cable with a System 80 50 pin connector at one end and a TRS-80 40 pin connector at the other, System 80 fans could avail themselves of the many TRS-80 accessories.

3.1 Exatron Stringy Floppy

The amazing Stringy floppyThe Exatron Stringy Floppy (ESF) was an inexpensive option for high speed storage (err...higher than cassette tape at any rate) without the expense of going to a disk-based unit. The unit was produced by Exatron Corporation, 181 Commercial Street,Sunnyvale, CA 96086, USA.

The unit consisted of a small drive, designed to read and write to wafers of continuous tape. These wafers, about the size of a credit card (well..a couple of credit cards stacked on each other), were read at very high speed. What could take 10 minutes with tape would take 10 seconds with an ESF. What's more, the unit would work with 16k RAM (disk needed at least 32k), and ESF operating system was firmware, built into the unit and using some of the unoccupied RAM between the 12K ROM and the start of free memory at 4300H. This means cassette-based programs did not need to be offset, as they did in disk-based system, where the free memory started at 5200H. As a bonus, a keyboard de-bounce routine was in the ESF ROM curing cassette-based units of this keyboard plague.

The units were initialised from cassette basic by typing SYSTEM, then /12345 <new line>. After that, you could use the commands @load , @save to access files on the tape etc.

The ESF was a popular option. However, it wasn't a perfect solution. Wafers wore out eventually (sometimes rather quickly), leading to parity errors and occasionally the ESF would eat a wafer, resulting in a noise which was horrible to hear. Then it was all hands to the tweezers to extract the thin tape from the innards of the machine.

The beast itself!The wafers came in a number of different lengths and the 50' ones in particular would be prone to failure (or being eaten). Users always kept their original software on cassette tape...just in case.

I owned one of these units so know a lot about them. It still lies boxed up with my original System 80.

The ESF was eventually eclipsed as disk drives became more standard and expansion costs fell. However, it lives again in emulation and virtual wafers for the ESF can be downloaded from this site.

3.2 MicroMint Disk-80 Expansion Unit

The MicroMint Disk-80 Expansion Unit was a third-party expansion unit for the TRS-80 Model 1. To tell the truth I'm not sure just how popular they were with System 80 owners, but they were available to Australians so I suspect a few folk had one of these hanging off their computers. The manual for this expansion unit (courtesy Dirk Stoffels, Canberra) is available here.