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Hi too

Postby monzamess » Sat Aug 14, 2010 3:41 pm

My first "real" computer (i.e. one with a disk drive) was a PCjr. My dad and I would hit closeout sales around town and in 1985 we found a NIB 128k PCjr for $100. I think they had just been discontinued but that was still a steal. I also had the thermal printer and a green-screen composite monitor. If I wanted to play games in color I had to hook it up to my ancient color TV with an RF modulator. If I wanted to hear the sound I had to use a tape recorder as a ghetto amplifier since I didn't have speakers. I wrote all kinds of BASIC programs, called BBSs with my 300-baud modem, and generally cut my teeth on it. I had the black carry case and took it on trips and to school. I sold it (with a couple of minor upgrades) in 1987 for $600! I used the money to buy an Atari ST. I also had some other machines (Atari 8-bits mainly) that I traded around.

I ended up with another PCjr around that time (which worked fine), and I carried it around for over 20 years though it didn't see much use. I just unpacked this machine last month and it does not work. Dead as a doornail. I didn't check the power supply with a meter but I suspect it's the culprit. I also have two PCjr joysticks, a printer attachment (I think--I know what one looks liked but I haven't looked at it in a while), a few cartridges, and a bunch of old disks.

Anyway, I just won a 128k PCjr and color monitor (I used to dream about having an official color monitor) on eBay. It was listed as-is but the picture showed that both the computer and monitor could at least power up and display BASIC, so I hope when it arrives next week that I can make a working system again between it and my current unit.

If it does work I'll be hunting for memory and speech sidecars. I don't think I want to go as far as upgrading the CPU, Tandy mod, clock, etc (and all the other stuff I used to dream about) but I know 128k is tight!

I wonder if the drive out of a PCjr will connect to the floppy controller on my Pentium 4 PC? I have a HD 5.25" drive with cable that I just recently removed from that machine, but I'd rather use the 360 drive since there are problems with 360k disks in the HD drive (right?).
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Re: Hi too

Postby monzamess » Wed Aug 18, 2010 6:38 am

I got the PCjr yesterday. After cleaning up a few smudges, it looks and runs like new. I was also able to determine that my older PCjr is OK but its power brick is dead.

My core i5 laptop makes a good keyboard riser. :)

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Re: Hi too

Postby Brutman » Wed Aug 18, 2010 6:00 pm

Hello, and welcome!

Sorry about the slow response - life in the non-PCjr world has been very hectic lately. I don't know where everybody else is hiding either.

I've never bumped into a bad power supply, and I think that people generally are too quick to blame them. Go ahead and check it with a meter, but obviously be careful - it still outputs 17VAC which is enough to give a shock. If it really is dead there is a fuse buried inside it, but breaking in to get to it is a challenge.

The PCjr floppy drive is just a standard half-height floppy drive. You are more likely to have problems with the BIOS not supporting 360KB diskette drives, or the motherboard not having a floppy port at all. I've successfully run full height single Tandon drives on Athlon 2000 class machine under Linux, so it can work if the motherboard and BIOS have support.

You can write double sided diskettes in a high density drive, but they should be bulk formatted first because the double sided drive has a wider head than the high density drive. Sometimes it works without bulk erasing - your mileage will vary.


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Re: Hi too

Postby monzamess » Sat Aug 21, 2010 4:11 pm

Thanks for the reply.

Not much PCjr time for me either but I got out my old disks of programs I wrote when I was 11-12 yo. Some disks are still good, some aren't. Some of the stuff I barely remember and some feels like I wrote it yesterday.

I backed up all the stuff to a modern PC a while ago but it's more convenient when the original 5.25" DSDD disks just work in the first place. :)

Also found a copy of Alleycat and I still stink at it but this might have been the first time I heard its 3-voice soundtrack.

I dug my 5.25" HD drive out of storage, and it will definitely work on my desktop PC unless it's broken, but first I have to deal with the computer's failing HD (again... yay Seagate). The 360k drive probably won't work but I will double check what the BIOS supports, who knows.
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Re: Hi too

Postby jmetal88 » Sat Aug 21, 2010 9:51 pm

Just so you know, I've never seen a BIOS that didn't support 360k floppy drives. I even had a computer with one of those crappy controllers that only lets you use one floppy drive, and it still had choices of 1.44M, 720k, 1.2M and 360k.

EDIT: Actually, I take that back. I may have had a Compaq once that only supported 1.44M and 720k drives, but in that case, it's understandable, as it had a proprietary form factor with no physical space for a 5.25" floppy drive (and the motherboard could not have been mounted in a generic case without significant modification).

EDIT 2: I also remember I had a Compaq in a standard ATX case shortly thereafter, and it did support both types of 5.25" floppy drives.
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Re: Hi too

Postby monzamess » Wed Aug 25, 2010 5:57 am

Turns out my computer BIOS indeed supports 360k drives. Unfortunately Windows XP does not! I duplicated the problems in this discussion: http://www.vintage-computer.com/vcforum ... 12280.html

I was able to plug the 360k jr drive into my PC and boot into DOS 3.3, which was pretty cool for the sheer novelty of it, but that doesn't do me much good. :roll: All my machines are XP or higher so the 360k is out for all practical purposes and resting comfortably back in its original PCjr home.

I still have a 1.2MB drive to try. I understand that XP should be fine with 360k disks in a 1.2MB drive so we'll see.

I wonder if this could work with a PCjr? http://www.mmj.pl/~lotharek/atari/www/sd%20floppy.html

It supports PC but only lists 720K and 1.44MB formats -- does jr do 720K?
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Re: Hi too

Postby jmetal88 » Wed Aug 25, 2010 8:08 am

From what I understand, PCjr is capable of reading 720k floppies, but not booting from them. I've heard there is some way to format a 720k floppy so that it looks as if it's a 360k floppy, which makes it bootable. It's described in the PCjr Club Library archive mentioned on one of the other pages of this site. I only skimmed the article though, so I could be misunderstanding.
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Re: Hi too

Postby Brutman » Wed Aug 25, 2010 8:51 am

The trick is pretty simple - format the 720K floppy with only 40 tracks instead of 80. In fact, if you have a Linux machine or a utility that reads and writes disk images under DOS, you can just 'slam' the image of a 360KB diskette onto a 720KB diskette and it will work fine.

The only difference between a double density 5.25" diskette format and a double density 3.5" diskette format is the number of tracks. Sectors per cylinder stays the same, which is why it works.

From the controller point of view both double density formats use the same data rate. So the machine is physically capable of driving a 720KB drive. It's just a matter of getting DOS to use more tracks than the BIOS reports. This can be done with a device driver. (Device.sys I believe.)

My memory is fuzzy here but later versions of DOS inspect the boot sector of the floppy diskette to see what the format is, and might use that regardless of what type of drive you say you have. These machines don't have a CMOS memory setting to tell the OS what type of drive is available, so the OS either tries to seek past track 39 or it uses what is on the boot sector of the drive. (If you can seek past 39 you have at least a 1.2MB or a 720KB drive, but that's till not enough to tell the difference between 720KB, 1.2MB, and 1.44MB formats.)
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Re: Hi too

Postby monzamess » Thu Sep 02, 2010 6:46 am

The SD solution would be cool. For now I'd be happy to get my 1.2 floppy working in a PC again, and just buying some 5.25 DSDD floppies off ebay, in order to get files to/from the jr. I think I might have killed the 1.2 drive. When I install it, it makes the distinctive "drive check sound" during computer startup, but then I get a floppy error and that's it. My other PC (a p3-era thing) has BIOS support for the drive but only recognized it once. I need to reeducate myself on how floppy cables work, where the twist goes, etc, and double-check--when real life lets up a bit. :)
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