Legacy Technologies
PCjr Expansion

Two designs were available. The 'Legacy' series was an expansion chassis that sat on top of the PCjr system unit. The Volksbox was designed to stand alone away from the system unit. Both units connected to the PCjr through the sidecar expansion bus on the right side of the PCjr. Both units also featured the 'L-Bus' expansion slots and room for either a floppy drive or a hard drive.

Expansion cards included a memory card, a clock/calendar and parallel printer port card, and a hard drive controller. All of these cards were specific to this expansion unit - they were not industry standard in any way.

If you wanted to use a second floppy drive you needed to purchase a new floppy controller to replace the one inside of the PCjr, which was only capable of supporting one floppy drive.

The Legacy expansion units were especially pretty - they were firm believers in 'Blinkenlights'. Here is a closeup of a running machine to show you what I mean:

The lights were not just pretty - they could be used to give you an idea of what the machine was doing. You could tell if the machine was reading or writing memory, or reading or writing to an I/O port. The current address on the bus was shown in the lights with the most significant bits of the address represented on the left side of the display. All one megabyte of  address space available to the 8088 was shown. By looking at the lights you could tell if the machine was operating out of ROM (high addresses) or RAM (lower addresses). An improvement on the design would be to have a 'freeze' button to latch and hold the LEDs on the display. Because as nice as this setup is, I can't use it for hard core debugging if it is being updated at 4.77Mhz.

Below is a link to a video which shows the lights in action during the boot process:

As nice as the blinkenlights are, the overall design of the machine did not mesh well with the PCjr. It has some notable faults: The connection from the PCjr expansion bus to the expansion chassis is made by an unprotected ribbon cable. Ribbon cables are notorious for their susceptibility to noise. The ribbon cable also does not have a 'pass through', so other sidecars can not be added. (There is room to get one sidecar on before the ribbon cable gets connected.) If you use the optional Legacy floppy controller to control two diskette drives, the ribbon cable has to pass through the lower case to the expansion unit. The ribbon cable is as poorly protected as the ribbon cable that connects the busses. The expansion deck sits on top of the machine, but is not attached to it at all. Trying to pick it up without thinking will damage the ribbon cables. The optional Legacy floppy controller can control two drives, but it does nothing to tell the BIOS of the machine that two drives are installed. You still have to boot with a device driver to patch the BIOS to recognize the second drive. Contrast these shortcomings with the Racore expansion units - the Racores are firmly attached, allow for further sidecar expansion, and they patch the BIOS of the machine to give you seemless support of the second floppy drive.

The internals of the expansion chassis appear to be well designed though:

• The case is metal with options for rear mounted expansion ports and a cooling fan.
• The power supply is small and well protected. It also uses a standard line cord instead of the non-standard PCjr power transformer.
• The expansion bus is easy to get at. (Too bad the one in this picture isn't very well populated.)