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My "New" PCjr Plays Led Zeppelin!

PostPosted: Tue Aug 14, 2012 7:48 pm
by balsino
Greetings from Tucson! Well, Mike's exciting news of his new PCjr bootable hard drive BIOS got me inspired to work on my jr collection this summer. Plus, I was sidelined for 2 months recovering from pneumonia. So, no going to the gym, and no playing the guitar. So instead of reaching for my stamp collection like I usually do when I am sick, I reached for my PCjrs for the first time in 6 years. A picture of my "New" PCjr is here: ... GjJu5ZNGHJ

I literally spent dozens of hours building this 4 level high PCjr beast. I had 3 working PCjrs, and combined all of them into 1 working machine, the best of breed, from many, one. More importantly, I finally took Mike's advice and got rid of my sentimental Racore Drive 2 and abandoned PC DOS 5 for PC DOS 3.3 and am really happy on how it turned out. My PCjr consists of a 360 KB drive on the first level, a 720 KB 3 1/2" Micro Diskette drive on the second level, a 340 MB Conner SCSI drive on the third level, and a Maxtor 212 MB SCSI drive on the 4th level.

The power supply is an internal 150 WATT PC Enterprises (PCE) Power Supply that is 2 levels high. So this forces me to use the PC Enterprises 2 level high PCjr diskette controller card, which does not natively recognize the 720 KB drive without software, as did my RACORE controller I used the past 27 years. My sidecars are the: (1) PCE Seagate SCSI; (2) 512KB Memory; (3) PCE DisplayMaster VGA; (4) PCE GameMaster Adlib Sound With Bus Mouse, (5) Mike's modified LPT1 Parallel Printer, and (6) Mike's modified LPT2 Parallel Printer. I use 2 cartridges, a PCE BIOS cartridge, and a PCE VGA cartridge. I use DiskManager boot software so that PC DOS 3.3 recognizes partitions greater than 32 MB. I use a PCE bus mouse and a DataDesk 101 Key PCjr keyboard, with a NEC MultiSync VGA monitor, and 2 IBM PCjr joysticks. A PCE jrExcellerator brings the speed of the jr to 9.4 Mhz, almost an AT speed.

It took forever to get the right combination of jumper BIOS settings to work on the Seagate SCSI sidecar. Besides, I had 3 of these Seagate SCSI controllers, and 2 of them would not work. Finally, I moved the BIOS chips around and found that 2 of them would work okay, so now I have one backup controller. For fun, I even put the Future Domain BIOS chipset on the controller and tested it on the PCjr, and got as far as the Future Domain TMC850M message. Notice in the photo that I had to cut out the sidecar on the top to snake the SCSI ribbon cable out of the sidecar and to the back of the PCjr. This was because that was the only way the SCSI controller would remain stable. The other problem was that the SCSI controller would give memory errors and did not work with the PCE Megaboard or PCE 512KB Memory sidecars. Surprisingly, it only worked with an IBM 128KB memory sidecar that had been upgraded by PCE to 512KB. Also, bye bye to the speech attachment, it will not work with the PCE Seagate SCSI controller.

On LPT1 I have an IBM PC Graphics Printer, an HP LaserJet 6MP, a Backpack 3 1/2" 1.44 MB Diskette Drive, and a Backpack 4X CD ROM drive. It is the Backpack CD ROM drive that plays Led Zeppelin! There is a handy DOS utility that comes with it called TRKPLAY that runs the music CD in the background. Very cool, and I have the PCjr hooked up to my TEAC Stereo amplifier. I had to take the CD ROM drive apart, disconnect the internal audio cable, cut a hole in the plastic drive case, and route an audio cable from the CD ROM drive to my GameMaster Adlib sound card. It sounds great.

Anyone who has a PCjr can also play music CDs if you buy one of these BackPack parallel printer port CD ROM drives, as there is an speaker output on the drive to hook up to your stereo, and you could still use the TRKPLAY utility without the GameMaster sidecar.

LPT2 has a Xircom parallel printer port network adapter attached to it, and I log in to a Novell Netware 3.12 server I have set up. My next project is to add my BackPack 40 MB tape drive to it, and try to see if I can connect the Xircom over the network to a SUSE Linux 11 server SAMBA Share. One disappointment is that suddenly after 6 years, my BackPack 1.2 MB Floppy Diskette drive no longer works, which has me stumped. And I miss messing with my speech attachment.

But this PCjr has been stable as all get go, and I have waited 6 weeks before posting this to make sure the system is really burned in, and it is. It is great to be booting off the C: hard drive, and not get any error messages.

My previous PCjrs used Adaptec MiniSCSI parallel port adapter cables for SCSI device expansion and could not boot from the hard drive, so I am definitely enjoying this "new" PCjr.

Re: My "New" PCjr Plays Led Zeppelin!

PostPosted: Tue Aug 14, 2012 8:52 pm
by Brutman
We need a bigger picture!

Your "FrankenJr" is in a word, awe-inspiring. Something that big and hacked up should be blowing fuses ..

The DisplayMaster and GameMaster are truly unique - I don't know of anybody else who has either one.

While I was a big fan of the SCSI controllers (especially the Future Domain based ones), the current jrIDE is vastly superior. Well, maybe not - I haven't checked a CD-ROM on it yet, but for hard drives it is great. Especially if you substitute in a Disk On Module (flash storage) instead of a hard drive. On your system that would let you "slim" down by getting rid of the memory side car and the SCSI sidecar, and just having one to replace them. If you used FLASH based storage that would also get rid of two levels on your four level beast. As a bonus you could put the speech sidecar back on ...

How does DiskManager work? I thought that 32MB was an inherent limitation in DOS 3.3 that could not be fixed.

Re: My "New" PCjr Plays Led Zeppelin!

PostPosted: Wed Aug 15, 2012 6:00 pm
by Vorticon
Very cool indeed. I was thinking a while back about adding a Backpack parallel CD drive, but I already have a Backpack 3.5" diskette drive connected to LPT1, with LPT2 being used by my network card. Can one piggyback a Backpack device to another using the printer port on the first one?

Re: My "New" PCjr Plays Led Zeppelin!

PostPosted: Wed Aug 15, 2012 8:26 pm
by balsino
Frankenjr sounds cool! I will try to get a bigger picture if someone shows me how to embed the photo in the forum post.

Anyway, Diskmanager works as a device driver called DMDRVR.bin, which of course sucks up memory. PC DOS 3x sees it as one big partition. So using it I actually have over a 300 MB partition on the first hard drive and a 212 MB partition on the second drive. I don't worry about blowing a fuse because the 150 Watt internal power supply (which is noisy) is pretty efficient. So I gained desktop real estate by losing all the PCjr power bricks, but traded it for noise. Oh well.

Yes, you can daisy chain multiple Backpack devices off of each other. I have gone as high as 4 parallel port devices chained that way on my previous PCjr. No issues what so ever. I run both the 3 1/2" BackPack Diskette Drive and CD ROM Drive at the same time without any issues.

It's pretty cool getting caught up on the jr forum. That BASIC program in 256 colors really has my interest. So does that "new" serial MIDI card. I tried building that MIDI port back in NJ in 1993 either from instructions from jr Report or jr Newsletter (I can't remember which) but the instructions lacked detail. One of my friends is a retired design engineer from Texas Instruments, maybe he can help me build that PCjr MIDI serial port, which was always one of my big PCjr dream projects.

Yes the Future Domain was the cooler SCSI card for jr, but remember, in 2006 my last Future Domain card was broken, so I resorted to the Adaptec MiniSCSI cables. When I pulled out my jr parts this summer, I had forgotten that I had 3 Seagate SCSI jr controller cards. Those cards were always known to me to only work on 40 MB disk drives, and never anything larger than that, even though PC Enterprises advertised an 80 MB drive would work with it in their 1989 catalog. I spent days just trying to get those Seagate SCSI cards working with the hard drives before even trying to assemble the rest of the jr.

Yes, I agree that the Seagate SCSI controller is funky, but so far so good. PC Enterprises documentation says it should work with the Speech attachment and its other memory cards, and lists tables for the proper BIOS jumper settings, and I did choose the ones that would work with the speech attachment, but no dice.

I have enough PCjrs to build a slim downed version like you describe, but I wanted to remove as much cluttler in my house as possible, so I "consolidated" my jurniors and stored the rest in closets in large plastic tubs. I have too much work computer gear-a BladeCenter and 2 rack servers in my home office and guest room, and am running out of space.

Now the challenge is actually to use the jr and play games on it, etc.

Re: My "New" PCjr Plays Led Zeppelin!

PostPosted: Fri Aug 17, 2012 4:13 pm
by jltursan
Still shocked after studying your setup!, how have you managed to get and assemble such varied hardware?!. More hires pics, please! :shock:

I'm also building a "minimal" (compared to yours) machine to run as much software possible. Still too many mods to reach your level ;). If I've also some spare time, I'll try to explore to Cartridge BASIC (practically no info in the net :() and other languages. Twenty years ago I coded some machine code demos on plain VGAs and the PCjr video looks really fun to master.

Re: My "New" PCjr Plays Led Zeppelin!

PostPosted: Fri Aug 17, 2012 7:40 pm
by balsino
Well I have tried to take better pictures, the link is below. Run the slideshow in the link, you will see many photos of the rear of the box. It was an unusual cloudy day here in Tucson, and despite all my lights in the home office, the lighting isn't the best in some of the photos (I avoided using a flash). ... 7e8de83cba

There is nothing shocking about the setup. PC Enterprises specialized in PCjr addons, and almost all of my setup is using PC Enterprises components. Think of the entire assembly as a "Kit." PC Enterprises even resold the BackPack options I have, so I knew they would work on the PCjr even though I bought those devices from Ebay many years after PC Enterprises stopped selling jr products.

The key to having fun on the jr is making sure you have plenty of memory, and to add a NEC V20 chip to get a faster clock speed. Mike specialized in many add on devices, like Zip drives, years before his latest BIOS/Hard drive break through.

If you want to add a hard drive, all you need is the Adaptec MiniSCSI cable, and any SCSI 2 hard drive of around a gig or less of storage in an external SCSI case. I found that many used vintage Apple MAC SCSI devices from the mid and early 90s like "PowerUser" and "LaCie Tsunami" work just great. You can get an Adaptec MiniSCSI cable here: ... B0053DLZ6C

You won't be able to boot from the hard drive, by you can do a Comspec C: command to transfer DOS control to whatever hard drive you have attached.

Other parallel printer attached hard drives usually work great on the PCjr too, escpecially if you modify the printer sidecars as Mike shows.

Re: My "New" PCjr Plays Led Zeppelin!

PostPosted: Sun Aug 26, 2012 10:54 pm
by Eric
balsino wrote:Image

I needn't be said that your little junior's growth spurt has left it bigger and much more capable than most upgraded 5150s. It makes senior look more like junior. XD Too bad it still suffers lack of DMA. Unless there's some way you've worked that into the system. You said it has a different bios?

Re: My "New" PCjr Plays Led Zeppelin!

PostPosted: Mon Aug 27, 2012 5:52 pm
by balsino
Yes, the BIOS is in a cartridge from PC Enterprises, called the "Combo Cartridge Version 3.0" which includes the BIOS patches and fixes for the jr that PC Enterprises developed. However, there is not any DMA, and that has always puzzled me. Racore had an awesome DMA board that worked with its Drive 2 level. I used it from 1987 through 1993. However, as I started becoming a PC Enterprises customer, Pat Calabria (the owner and developer) convinced me that the Racore DMA was not a good thing, and that I really should remove it. So I did. I never had any problems with that DMA board and I thought it made my PCjr work really well. In retrospect, I think the reason PC Enterprises was not a fan of the Racore DMA was that their many jr products did not work well with that DMA.

Re: My "New" PCjr Plays Led Zeppelin!

PostPosted: Mon Aug 27, 2012 7:06 pm
by Brutman
DMA frees the processor to do other work while memory is being transferred, but on a DOS system the processor does not have anything else to do anyway. It was used on the PC and XT because using PIO through the processor is horribly slow. By the time the 80286 became available (and the ability to do REP IN or REP OUT with it), DMA was not used for hard drive access in the BIOS. It did not come back until modern OSes brought it back.

The 8088/8086 does not have REP IN or REP OUT, but the NEC V20 does. The jrIDE design gets around this by using memory mapped registers so that we can use REP MOVSW instead. It is a more complicated design than using port I/O, but it's wicked fast. (Thanks Alan!)