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PCjr Options and Accessories

Some of the most fun things about the PCjr are not the machine itself, but in all of the cool options that were made for it. The PCjr was kind of an oddball: limited expansion, cartridge slots, non-standard connectors, and sidecars. This means that many options for the PCjr are unlike anything else designed for the rest of PC family.

When the PCjr was announced lots of companies jumped on the bandwagon. IBM had been so successful with the IBM PC that anything it put its name on would be gold. Well, things didn't quite work out that way. You'll see some mainstream PC companies here like Quadram, Spinaker, Microsoft, Lotus, and AST. As the PCjr market fizzled out smaller companies such as PC Enterprises, Racore, and ES Quality Products moved in to fill the void. By 1986 PCjr products were definitely a niche market.

The following tables give you a partial list of the options that were available for the PCjr. The more interesting options are described later.

Cartridges (Utility):

Name Manufacturer Description
QuickSilver Synectics System ROM patch to speed the boot process. Works by skipping some of the memory testing the machine normally does on a cold boot.
Compatibility Cartridge PC Enterprises Patches BIOS to make the machine operate more like a PC. Can be used to run much software that previously required patching.
Combo Cartridge PC Enterprises Several different BIOS patches in one cartrdige; Three versions were produced. Version 1.0 combines the Keyboard Buffer cartridge and the jrVideo cartridge. Version 2.0 adds the QuickSilver cartridge. Version 3.0 adds the Compatibility Cartridge.
Configuration Cartridge PC Enterprises Has dip switches on it that allow you to set the number of disk drives (up to four) and the video mode that the PCjr boots up in. Also lets you change the 'ID' byte in ROM to make the PCjr report itself as a PC.
Configuration Cartridge Plus PC Enterprises Same as above, but with LED status lights for Caps Lock, Num Lock and Scroll Lock. Uses a device driver to turn the lights on and off.
jrVideo PC Enterprises Replaces system BIOS routines with slightly faster versions, increasing the speed of video writes on the system.
Keyboard Buffer PC Enterprises Altered ROM BIOS to allow the keyboard to be used while the diskette was active
PC ID Racore BIOS replacement: make the Jr identify itself as a PC
Clock cartridge Integrity Technology A clock/calendar on a cartridge based on the Dallas DS1215 chip.
Blank Cartridge Integrity Technology A blank cartridge that you can use for your projects.

Cartridges (Applications):

ColorPaint Krepec Drawing program
Cartridge BASIC Microsoft Enhanced BASIC, PCjr only
Lotus 123jr Lotus Development An early version of Lotus 123
Electric Desk Alpha Productivity software
Andrew Tobias: Managing Your Money MECA

Cartridges (Games):

ScubaVenture
Gebelli
Game
River Raid Activision Game
PitFall II Activision Game
Mouser Gebelli Game
Demon Attack Imagic Game
Micro Surgeon Imagic Game
CrossFire Sierra OnLine Game
Mine Shaft Sierra OnLine Game

Cartridges (Educational):

FaceMaker Spinaker Game/Education
KinderComp Spinaker Game/Education
Fraction Fever Spinaker Game/Education

Memory Expansion Sidecars:

MS Booster Microsoft 128KB memory with bus mouse, and clock/calendar chip
JrCaptain Tecmar 128KB memory, parallel port, and clock/calendar
JrCadet Tecmar "Piggie back" board for the Jr Captain to provide additional memory
(various) Impulse up to 512KB memory, parallel port, clock/calendar
(various) AST Research 128KB, 256KB, or 512KB memory upgrade
jrSidecar PC Enterprises 128KB, 256KB, and 512KB memory upgrades

Keyboard Enhancements:

Keyboard Adapter Racore Allows you to use a real PC or PC XT keyboard on your PCjr
KB5150jr Keytronic Full size replacement keyboard designed especially for the PCjr (PC Layout)
KB5151jr Keytronic Full size replacement keyboard designed especially for the PCjr (AT Layout)
KB5149jr Keytronic numeric keypad add-on for the PCjr

Expansion Chassis:

Drive II Rapport/Racore 384KB additional memory (opt), parallel port, 2nd diskette drive (opt), and clock/calendar
ATcessory Racore 1.2MB floppy drive, parallel port, clock/calendar, DMA controller
Legacy I Legacy 256KB or 512KB memory (opt), clock/calendar (opt, printer port (opt), fixed disk controller (opt)
Legacy II Legacy As above with second diskette drive and diskette drive controller upgrade
Legacy III Legacy As above with 10MB hard drive instead of a floppy drive
Volksbox Legacy external (not top mounted) expansion chassis for hard drive or floppy drive, memory, clock, etc.
Model 210 Impulse external (not top mounted) chassis for second diskette drive
FX-500 Xetec expansion chassis for 2 3" floppy drives. (Yes, 3", not 3.5")
TriDrive Coalescent Tech. external (not top mounted) chasses for up to two external diskette drives

Miscellaneous Internal Upgrades:

Drive controller Legacy Enhanced floppy drive controller; replaces original floppy drive controller
Math coprocessor Legacy 8087 upgrade
The One Card Legacy memory upgrade to 512KB
Drive IIA Creative Firmware Expansion card for modem slot that allows for an external diskette drive
NEC V20 (various) replacement for 8088 to give a slight speed boost
jrExcellerator PC Enterprises A speedup board that plugs into the 8088 socket. Provides an extra 16KB of RAM that can be used to 'fill' the memory hole created by the PCjr video memory setup.
Jr Hotshot ES Quality Products memory upgrade to 512KB
Jr Hotshot Multi ES Quality Products 256 or 512K memory, clock, diskette controller
Serial card Legacy Adds a serial port; uses the internal modem slot
ThinFont PC Enterprises Allowed you to change the text-mode font between "normal" and "thin" letters
jrROM-Clock PC Enterprises Adds a clock and calendar to the PCjr. Installs 'underneath' one of the system BIOS chips. This is probably the Dallas Semiconductor DS1216E chip which is discussed elsewhere on this web site.
2400 bps modem PC Enterprises Finally, an appropriate internal modem. This modem used the Hayes command set and used non-volatile RAM to store the configuration instead of DIP swithes.
SCSI card RIM A simple SCSI card that sits in the modem slot. No BIOS - does not boot a hard drive on it's own. An optional cartridge can provide that capability.

Miscellaneous Sidecars:

Parallel Port IBM Adds a standard parallel port to the PCjr
Speech Adapter IBM Speech synthesis adapter
Power Sidecar IBM Provides additional power for when you have many sidecars on the PCjr
ST01Jr PC Enterprises SCSI card! Uses the Seagate ST01 chipset.
TMC 850Jr PC Enterprises SCSI card! Uses the Future Domain 950 chipset
Cluster Attachment IBM for networking with other PCs using Cluster cards or Cluster Attachements
Display-Master PC Enterprises A sidecar that adds VGA support; up to 800x600 in 16 colors is supported.
jrBus-Mouse PC Enterprises A bus-mouse sidecar using a Microsoft Bus mouse. (Yes, they worked with MS on this.)
Megaboard PC Enterprises Adds 256KB to 1MB of memory to a Jr. Memory above 736K is used for a ram disk.
GameMaster PC Enterprises This sidecar adds Adlib and SoundBlaster compatible sound to your Jr. Also implements the 'Tandy mod' without requiring soldering or other modification. Optionally includes the 'jrROM-Clock', a bus mouse, and either 128K or 256K of memory. (The memory is used to bring the machine from 512 or 640K up to 736K.)

Other Accessories/Upgrades:

Siamese Adapter Synectics Allows you to put two cartridges in one slot
Koala Pad Koala The classic Koala pad from the 8 bit days.
Buss Adapter Unknown One of several adapters that let you use standard PC cards on a Jr
Muppet Learning Keys Keyboard Sunburst Software A kids style keyboard that actually connects through the joystick port.

Some notes on the various options ...

PC Enterprises Configuration Plus Cartridge

    This little gem is almost like a Swiss Army knife:

    • One switch allows you to change the ID byte of the machine to make it look like a PC instead of a PCjr.
    • Two switches let you set the number of diskette drives, much like the switches on a PC or XT motherboard.
    • Two switches let you set the display type to something other than the default 40 column color display.
    • Three LEDs track the state of Scroll Lock, Caps Lock and Num Lock, as the machine reports it. Unlike the keyboards that do this, the cartridge won't get out of sync with the machine. (It requires a TSR to operate though.)

    The docs for this can be found here.
    PC Enterprises Configuration Plus Cartridge

River Raid and Pitfall II

Classics ... what more does one need to say?
River Raid cartridge Pitfall cartridge

Demon Attack

Demon Attack cartridge

Demon Attack by Imagic is a classic "kill the aliens in space" game originally released in 1982 for the Atari 2600 and ported to many other machines, including the PCjr.

The PCjr version took advantage of the extra color and sound available on the machine, making it competitive with the other machines that were designed as game consoles. Space on the cartridge was limited so Imagic did not implement a title screen - when the machine boots it goes right into the demo mode of the game.

If you would like to see a sample of the graphics and the sound from the game take a look at the YouTube video to the right.

Integrity Technology Clock Cartridge:

    Like other 8088 class machines, PCjrs did not keep time while they were turned off. There were many clock/calendar solutions for the Jr, usually packaged along with other things in a sidecar. One of the more unique clock/calendar solutions was this cartridge sold by Integrity Technology. Cartridges are 'read-only' on a PCjr because there is no write circuitry, yet you can set the date and time on this cartridge. The trick is in the Dallas Semiconductor DS1215 chip, which makes up the heart of the cartridge. (Email me and I'll tell you the trick.) If you need software to drive one of these drop me an email. I just recently (Jan 2006) wrote a small C program that can talk to this cartridge and set the DOS date and time accordingly. Integrity Technology Clock cartridge

Synectics Siamese Adapter:

Have you found that two cartridge slots are not enough? Have no fear! This adapter turned one cartridge slot into two. As long as none of the cartridges you were using conflicted, it didn't really matter how many you put on a system. Synectics Siamese Adapter

Integrity Blank Cartridge Kit:

    Want to make a cartridge of your own design? Integrity Blank Cartridge Kit

Racore Keyboard Adapter:

The Racore Keyboard Adapter allowed you to use a full-sized PC or XT keyboard on the Jr. You could also have your PCjr keyboard attached at the same time, just in case you needed to switch back and forth between the two layouts.
Racore Keyboard Adapter Racore Keyboard Adapter

The docs for this can be found here.

Keytronic KB5150jr:

    The Keytronic KB5150jr keyboard is a great replacement for the PCjr keyboard but it doesn't have the infra-red communication feature so it must always use it's keyboard cord. It features Numlock and Capslock lights, which are managed by the keyboard. The PCjr has no way to tell the keyboard if the lights should be on or off, so if a program sets the Numlock or Capslock it is possible for the keyboard to get out of sync with the computer. Unfortunately, this keyboard is not 'clicky' like the IBM PC keyboard using the buckling spring mechanism. It's rather mushy, and it's probably based on foam inserts under each key. Keytronics KB5150jr

Keytronic KB5151jr:

    Keytronics KB5151jr keyboard The Keytronic KB5151jr features a separate cursor pad which is activated and deactivated using a dedicated key. Although it resembles an extended keyboard, it is missing F11 and F12, as these had not been introduced by IBM yet. Like the KB5150jr the keyboard features indicator lights for Numlock and Capslock. It also uses foam inserts under each key, giving it a rather mushy feel. Early versions of this keyboard had a bug in them that would cause confusion between the numeric keypad and the cursor keypad. Keytronic provided an upgraded EPROM that eliminated the bug. If you have one of these keyboards and it doesn't have this bug, please contact me - I need a copy of this EPROM to fix my KB5151jr!

    The docs for this can be found here.

Keytronic KB5149jr:

    Keytronics KB5149jr keyboard Here is an add-on numeric keypad for the PCjr. It is designed to be used with the original PCjr keypad.

    The docs for this can be found here.

Rapport/Racore Expansion Units:

The Rapport and Racore expansion solutions are related. I think that Rapport turned into Racore. There are several variations of the product:
Early memory cards in the Rapport/Racore added 128KB of RAM to the system. There were sockets for 256KB more RAM, which would bring the daughter card in the expansion chassis to 384K, or 512K for the entire system. Chips were 64KB x 1 bit chips, organized in groups of eight. (Remember, this system doesn't have parity memory.) A later memory card has 512K on it, which brings the entire system up to 640KB. The clock and calendar is provided by an OKI 5832 chip. DMA is option on these units. Non-DMA units have a 24 pin BIOS EPROM. The DMA versions have a 28 pin BIOS EPROM and the extra DMA circuitry.

Docs for the Rapport Drive 2 Model 1200 can be found here. The Racore and Quadram units are similar.

PC Enterprises TMC 850Jr:

This is an amazing sidecar. Very hard to find too. If you find one, don't let it go. If you do decide to let it go, talk to me first. :-)
TMC-850jr circuit board
The TMC 850Jr is one of two PC Enterprises designed sidecars that adds a SCSI adapter to your Jr. This particular model is based on the popular Future Domain 950 chipset, which is a classic SCSI implemention from the early 90s. The DOS drivers support hard drives, CDROMs, and removable storage, and they seem to work on the Jr. With this adapter on your PCjr you can boot directly from a SCSI hard drive. The other model is based on the same chipset that Seagate used on their ST01 SCSI adapter. The ST01 chipset isn't as desirable; it's basically enough to boot a hard drive. And sometimes the BIOS extension that comes with the chipset is limited to boot only specific Seagate hard drives, which is borderline infuriating. (Later BIOS versions apparently removed this limitation.) I don't know of any ASPI drivers for the ST01 chipset, so a CD-ROM is probably out of the question. If you do enough research using Google, there is some folklore out there that says the two chipsets are very similar, and that the difference between them is just a few bit mappings in some registers. I've never seen specific enough information on either chipset to know if this is true or not. The thing that makes me think this is plausible is that my specific TMC 850Jr adapter has "ST01JR" stenciled on the card. On this card you will notice two EPROMs. One is for a ROM extension provided by PCE which includes some utilities available from the DOS prompt. The other EPROM is the ROM extension that allows a PCjr to boot from this card.

Creative Firmware Drive II:

This little device sat between the diskette drive controller and the first diskette drive, altering some of the signals so that a second diskette drive could be added. It used the modem slot to draw power, and perhaps to snoop on some signals. (I need to analyze the wiring to find out exactly what it is doing.) The second drive was usually located outside of the PCjr in a stand-alone enclosure with its own power supply. One interesting little side-effect of this card is that both drives would spin when one was accessed. Unlike the Racore expansion units, this did not have enough wiring or circuitry to control the drive motors independently. Creative Firmware Drive II
The docs for this can be found here.

PC Enterprises jrExcellerator:

The jrExcellerator is a board that increases the clock speed of your PCjr from the standard 4.77Mhz to 9.54Mhz. You install it by removing the 8088 CPU under the disk drive and replacing it with this board, which fits snugly under the disk drive. (This is very similar to the Jr HotShot.) The board comes with a NEC V20 which replaces the original 8088 CPU. The board also has some memory configuration software on it which can eliminate the need to run a device driver to recognize extra memory.

PC Enterprises Thin-Font:

There is a little known hack on the original PC CGA card that allows one to alter the font that is displayed. The card has two fonts on board, a 'single dot' and a 'double dot' font. These fonts each take up 2KB, and are stored in a 4KB ROM module on the card. The 'double dot' font is normally used, but if you alter the card slightly you can change it to use the 'single dot' font. The Thin-Font module performs a similar trick for the PCjr. The PCjr font ROM only has the 'double dot' font. This replacement EPROM has both fonts in it. You can switch between the fonts by either using a toggle switch or by using the micro-clip and the included software. (The micro-clip would be attached to the output of a chip that could be controlled via software.) Many people found the 'single dot' font to be more readable on the PCjr monitor. This upgrade was fairly cheap and easy to do.

The docs for this can be found here.
PC Enterprises Thin-Font

PC Enterprises 2400bps Internal Modem:

The IBM internal modem (made by Novation) was only 300bps, which was obsolete when the PCjr was announced, and not much fun to use. At a time when 'Hayes Compatible' meant everything, this modem was slow and had its own command set. The PC Enterprises 2400bps used the same internal modem slot, but it was eight times faster and it was Hayes compatible.
PC Enterprises 2400bps Internal Modem

PC Enterprises Display-Master:

This sidecar adds VGA capability to a PCjr. It supports CGA, EGA, and other display modes, and VGA up to 800x600 in 16 colors which is technically an SVGA mode. The sidecar comes with connectors for the standard PCjr monitor and a standard VGA monitor. A cartridge with some BIOS modifications is required to make it work. Besides initializing the VGA card, the BIOS also eliminates the need for memory device drivers.

PC Enterprises Megaboard:

This might be one of the strangest memory cards ever produced.
The sidecar can hold up to one megabyte of memory. The memory is very flexible - if this is the only memory card on the system, it will take a stock 128K Jr and expand the conventional memory to 736K. (640K is the traditional limit, but the memory map on the Jr allows you to get to 736K.) Then, you'll still have 416K of what they call 'PCE memory' which can be used as a RAM disk. If you put it on a 640K Jr, it will bring conventional memory up to 736K and the rest of the memory (928K) will be available as 'PCE memory'. The 'PCE memory' is similar to EMS memory; it's accessed through a small window high in the memory map, and it uses a software driver to bank switch the visible portion. PC Enterprises didn't initially offer a true EMS driver, but they made one available later. The memory in this range does not get cleared by BIOS on a reboot, so if you were using it as a RAM disk the contents of the RAM disk would survive a reboot.

PCjr Buss Adapter:

The misspelling is theirs not mine - it's printed that way right on the card. This little beauty lets you plug 8 bit ISA cards into the sidecar bus of your PCjr. This is not for the weak at heart, and there are some restrictions:
  • The card can not use DMA.
  • The card is restricted to the available IRQs on the PCjr.
I will make the pinout and schematic available when I get around to it. I basically have the pinouts from a different source - I just want to make sure they match the pinouts used on this adapter. Using this adapter I have run a Trantor T130B SCSI card with a SCSI hard disk, A Future Domain 8xx series card with a SCSI hard disk, and various 8 bit Ethernet cards.
PCjr Buss Adaptor

Koala Pad:

The Koala Pad is an old school classic. It connects to the PCjr via a joystick port, and allows you to draw in a more natural way than a mouse or joystick allow. Koala Pad

Legacy The One Card:

The One Card is very similar to the jrHotshot. To install it you pry up the diskette drive tray, which reveals the 8088 CPU on the motherboard. You then very gingerly remove the original CPU and replace it with this board, which becomes a daughterboard to the motherboard. Room under the diskette drive tray is tight, so this this board has a fairly low profile. Unlike other boards, this board has the 8088 soldered onto it, so you do not reuse your existing CPU. This also makes an upgrade to a V20 not feasible, unless you are very good with a soldering iron and willing to take some risks. Solutions like this avoided a sidecar on the side of the system, but they put more of a load on the internal power supply and heated things up a bit.
Created November 30th, 2001, Last updated August 24th, 2008 (C)opyright Michael B. Brutman, mbbrutman at gmail.com

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