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PCjr flexibility

NeXT

NeXT

Veteran Member
Joined
Oct 22, 2008
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8,149
Location
Kamloops, BC, Canada
I'm having trouble figuroug out what to do with a PCjr. It's got the basics but essentials (360K floppy, 640kK ram, parallel port, serial dongle, joystick, Tecmar JrCaptain, and the typewriter keyboard). I thought it would be nice to drag it out to use for low memory games or BBS. I got no desk space but I have a shelf slot on the home theater but have no clue how well the "less than 50% compatible" part holds up for most games.
Does anyone else have personal experience on how useable it was?
 
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A co-worker bought an PCJr and outfit it with a hard disk, memory expansion and a bunch of other options. When I pointed out that he could have purchased a PCXT Far East clone for less money, he was not happy. I've never understood the fascination for the Peanut...
 
NeXT said:
I'm having trouble figuroug out what to do with a PCjr. It's got the basics but essentials (360K floppy, 128K ram, parallel port, serial dongle, joystick and the typewriter keyboard). I thought it would be nice to drag it out to use for low memory games or BBS. I got no desk space but I have a shelf slot on the home theater but have no clue how well the "less than 50% compatible" part holds up for most games.
Does anyone else have personal experience on how useable it was?
Click to expand...

I used one from March 1984 to early 1990 as my primary computer. It was also my "trainer" - I had no real experience with computers before owning one. (Just some limited exposure at school.)

The reports of the incompatibilities are overblown. I was able to run most programs just fine. The memory was the biggest limitation - 112KB was not enough to boot DOS and run a lot of later programs. 256KB is probably the minimal usable amount.

If you had to pick a class of software that caused problems, it would be bootable games. A lot of them programmed directly to the CGA metal and were tripped up by a slight incompatibility in the registers. That could be fixed with a simple DEBUG.COM patch. The timing was also different.

Diskette utilities that programmed the floppy drive controller were also a no-go. There was a special PCjr version of CopyIIPC called CopyIIJr that was equivalent.
 
One more note to clarify things:

After the introduction of the machine, most of the software houses cleaned up their act and either detected the PCjr hardware or stopped programming to the metal to initialize the video hardware. So the bootable games problem was mostly a teething pain. (But as the games became bigger it turned into not having enough memory.)


As for the appeal of the PCjr ...

  • Much less expensive entry point than an IBM PC
  • Expanded CGA+ graphics modes (Built-in)
  • 3 voice sound and a white noise generator
  • Built-in ports that were extra on other machines (serial port, joystick, etc.)
  • Cartridge slots that had the ability to provide games, DOS software, or even replace the system ROMs
  • Compact footprint; wireless (or wired) keyboard
  • Pretty good software compatibility out of the box .. As I said above, it ran most DOS apps easily.

Comparing it to an Asian clone is not fair - those were strictly clones of the PC and had none of the differentiators. This was supposed to be IBM's vision of what a home machine would look like in 1983. There were not too many Asian clones you could purchase in late '83 or early 84 and none of them had this feature set.

As for your co-worker, he would have been better advised to get that clone machine. By the time you could buy all of those upgrades to a PCjr everybody had already figured out that IBM had compromised the machine too much and it wasn't going to survive long term. (Tandy did a far better job with their PCjr compatible 1000 line.)
 
You can upgrade it. I still have 6 or 7 boards + parts kits for JR-IDE. Expands the Jr's memory to 736KB, adds 496KB flash disk (as soon as someone codes support - cough!), POST error display, RTC, and IDE disk interface. You only need to re-use the plastic side-car shell from another side-car.

http://www.brutman.com/jrIDE/jrIDE.html
 
eeguru said:
You can upgrade it. I still have 6 or 7 boards + parts kits for JR-IDE. Expands the Jr's memory to 736KB, adds 496KB flash disk (as soon as someone codes support - cough!), POST error display, RTC, and IDE disk interface. You only need to re-use the plastic side-car shell from another side-car.

http://www.brutman.com/jrIDE/jrIDE.html
Click to expand...

You have no idea how badly I want to get back to coding on that BIOS. My work schedule has been crazy for a few months, and I won't be clear for a bit longer.

Have you heard any comments or complaints on the existing BIOS? I haven't heard anything at all. I'm assuming/hoping that people are happy ...



Mike
 
Thank you Mbbrutman. That answers all my questions. I've also seen the jrIDE page before. Fun stuff. Too bad I con only fit one more sidecar on my system before it won't fit on the shelf. ;)
 
That was the intent .. to answer the questions.

The "flop" of the PCjr was seriously overblown. I spent years with the machine running all sorts of software - commercial packages, shareware, games, etc. As time went on the compatibility issue was less of a problem than just the lack of a hard drive and memory. There were plenty of memory options available, but hard drives were always very expensive because they were effectively a niche product. You could not just throw a generic ISA controller and a hard drive into the machine; you needed a custom card for the machine, a BIOS extension if you wanted it bootable, and an external enclosure.

Imagine how irritating a PC 5150 with one floppy drive and 128K would be in 1989. Same problem, except that the 5150 was far easier and cheaper to upgrade.

Here is some of the software I ran back then:

  • WordStar 3.3
  • Fontrix, PCPaint
  • Lotus 1-2-3 version 1A (from diskette, not the cartridge), Microsoft Multiplan
  • Sideways (print utility), AST print spooler, Borland Sidekick,
  • Procomm, Xtalk, Telix, Qmodem, etc ...
  • MS Flight Simulator 2.1, Kings Quest, Championship Boxing, Bop'N'Wrestle, Gato, Lode Runner, etc ...
  • More Shareware/BBSware than you can shake a fist at ..
  • Borland Turbo Pascal 3.0, Zbasic 3.x and 4.x, IBM BASIC Compiler 2.0
  • PC DOS 2.1 to 3.3 (unmodified), PC DOS 5.x and 6.x with a small patch

Copy protected programs were generally not a problem; they were using the BIOS routines to find the damaged sector on the diskette, so the lack of DMA was not an issue. (CopyIIJr made short work of those.)
 
Procomm 2.4.3 (for DOS) was fine, and I used it with an external Hayes 2400. (I love those beautiful aluminum cases designed to fit under the standard "Ma Bell" desk phone.) I used it for years for accessing BBSes and Unix systems at school. I had a NEC V20 which might have helped slightly, but the standard 8088 should have been fine too.

Procomm used direct access to the video buffer so screen drawing and scrolling did not cause character loss. Keyboard access is safe at 2400 bps too - the CPU can interrupt and deserialize the keyboard stream in between characters from the UART at 2400 bps. (At 4800 and above the keyboard using the Non-Maskable Interrupt is a problem.) During file transfers using Xmodem or Ymodem the diskette write was not a problem.

(It could have been a problem if the code fired off the NAK/ACK before writing to diskette, but in practice downloading was not a problem. As long as you do the diskette write first before sending the NAK/ACK, you would be safe.)

These days I just use Ethernet. The Ethernet device (Xircom PE-3) does some buffering so dropping packets/bytes is not much of an issue. Instead of getting data at 240 cps I get it at something like 26KB/sec, and that includes the write to the hard drive.


Mike
 
Are you loading the PE-3 drivers and a TCP/IP stack from floppy or your IDE drive? I'm used to DOS ethernet requiring a lot of resources to do much of anything.
 
I normally use the Xircom PE3-10BT and my mTCP code. The mTCP code can be run from a floppy drive and for something like Telnet or IRC that works fine. Doing FTP to a floppy drive is just painful, so for that you should have a hard drive.

Almost everything runs on a 256K machine. The exception is the FTP server, which can probably run in 256K but it will not support multiple connections.

For grins I can also use an NE1000 or WD8003 Ethernet card, but that requires a hardware hack to put the ISA cards on the PCjr sidecar bus. But it also demonstrates the level of compatibility between the PCjr and the PC - with the exception of the DMA signals and some IRQ usage differences, the 8 bit PC ISA bus can be pretty well mapped to the PCjr.

If your machine does not have at least 256KB on it you should consider upgrading it. Any member of the PC family would be challenging to use with just 128KB. Life begins at 256 ... and those of us with the jrIDE sidecar have 736. :)
 
I double checked the contents of my Tecmar sidecar when I was replacing its RTC battery and realized someone had already been in there and upgraded it to 512K. :) If mtcp is that nice I guess I'll give it a try.
 
To add to all that Mike has already stated: My love of the PCjr stems from what it introduced to the PC world, namely a 16-color graphics and 3-voice sound standard, which would help advance the PC as a gaming and entertainment platform. Granted, these standards were not actually made popular by IBM; rather, it was Tandy and their PCjr clone the Tandy 1000 which would catapult the graphics and sound forward. But it started on the PCjr, and you can get enhanced capabilities from a lot of software if you run it on the PCjr. Some of my favorite examples:

MS Flight Simulator 2.12+: 16-color graphics
Music Construction Set: 3-voice sound
Pinball Construction Set: additional graphics palettes
All Sierra AGI games: 16-color graphics, 3-voice sound
Thexder: 16-color graphics, 3-voice sound
Touchdown Football: 16-color graphics, 3-voice sound, and SPEECH

A nearly-complete list of games that support either the enhanced graphics, sound, or both can be found on mobygames here:

http://www.mobygames.com/browse/games/pc-booter/tic,2/ti,31/
http://www.mobygames.com/browse/games/pc-booter/tic,1/ti,32/
http://www.mobygames.com/browse/games/dos/tic,2/ti,31/
http://www.mobygames.com/browse/games/dos/tic,1/ti,32/

Some of the extra support may not work without either some modification of the PCjr hardware (the "Tandy mod") or the software, because it erroneously looks for a Tandy and only enables the extra support if found.
 
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