New PCjr user

General discussions on the PCjr

New PCjr user

Postby Cralt » Tue Jan 19, 2010 12:47 am

Hello!

I saved a PCjr from the trash helping a friend clean out an attic...

Its a bone stock unit with 128K and a LPT1 sidecar..

Im hoping to put it to use as a telnet/irc terminal to my OSX machine...

I just won a new in the box Xercom parallel NIC.. im waiting for this to show up now..

i got my jr to boot dos 3.3 with a disk that came with it. I copyed ircjr to the bootdisk using an old 1.2meg drive i had kicking around. When i tryed to load it I received an "Abnormal Termination" error and it dumped me back to dos..

I tryed copying some other stuff to me bootdisk but ended up wiping out the floppy by mistake..now i have no os :(

FreeDos does not boot in 128K

My question to this forum is this...

Can i run the packet driver for my NIC and ircjr in 128K?
and
How/where do I find a 360K image for a bootdisk for dos 2.X or 3.X?

FreeDos and Dos 6.22 do NOT boot with this little ram.


:ugeek:
Cralt
 
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Re: New PCjr user

Postby Brutman » Tue Jan 19, 2010 7:31 am

Hi Cralt,

You definitely need to get a boot disk. For a 128K machine DOS 2.1 or DOS 3.3 are your best options. If you have the ability to make diskettes from images received electronically then we can probably get you started quickly. At worst case you will need to get something to boot with through the mail.

I did a lot with a 128K machine years ago, but that is a fairly limited environment. It is slow because of the video memory wiring. After the standard 16K video buffer is subtracted you only have 112K for DOS and anything else. For games and BASIC applications it is a fine setup, but for more advanced things you will need to get to at least 256K.

As for my TCP/IP apps .. there is no way they will run in a 128K machine. You need 192K or 256K. If I stripped some of the functions from telnet and IRCjr it might work, but I would plan on getting a memory sidecar for the machine - it makes the machine much more usable.

Another good change to make would be on the parallel port. If you are handy with a soldering iron then modifying the parallel port to be bi-directional is pretty easy, and gives you a performance boost with the Xircom, Zip drives, parallel port hard drives, etc.

I haven't tried FreeDOS yet. DOS 6.22 might be able to boot, but not without being patched - it doesn't know about the PCjr video memory hole, and needs to be patched to get around it.


Mike
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Re: New PCjr user

Postby Cralt » Tue Jan 19, 2010 3:24 pm

Thanks for the quick reply

You definitely need to get a boot disk. For a 128K machine DOS 2.1 or DOS 3.3 are your best options.

I looked around a little but could not find 360K images for MS-DOS. I am set up to do RAWRITE/FDIMAGE from FreeDOS or dd/cat from a *nix machine...
It would be real cool to have the legit MS-DOS 3.3 disk set that I could just write protect and just copy when I run in to a PC project like this.

there is no way they will run in a 128K machine. You need 192K or 256K.

Major bummer... I'll just have to keep my eyes open for a side car with RAM. Do you know of any terminal programs that will run in 128K? No way a program like procomm or telix is going to run. I cant do ANSI color on 128K 6502 machine without the overhead of MSDOS (and a big chunk of ram going ot video) so im sure anything I find for this machine will bare bones ASCII only.

Another good change to make would be on the parallel port. If you are handy with a soldering iron then modifying the parallel port to be bi-directional is pretty easy, and gives you a performance boost with the Xircom, Zip drives, parallel port hard drives, etc.

Im not to worried about performance. Just want a good machine for telnet/IRC. I do alot of messing around with the TRS-80 CoCo but it makes a horrible terminal. This jr has a nice crisp display.

I haven't tried FreeDOS yet. DOS 6.22 might be able to boot, but not without being patched - it doesn't know about the PCjr video memory hole, and needs to be patched to get around it.


FreeDOS seems to have alot of bloat in it now. Im sure thats fine for a new machine but not so good for a 8088 machine. The way MSDOS 6.22 crashes makes sense now that you explained the funny memory map. It started to boot and said MS-DOS. Then it hit the drive again and hung. About 8 or 9 random characters showed up on the lower part of the screen.

The more I read about the little PCjr the more I can under stand why it failed so bad. This thing is so crippled its not even funny. I don't know how IBM got away with "PC" in its name :lol:
It is interesting though...
Cralt
 
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Re: New PCjr user

Postby Cralt » Tue Jan 19, 2010 5:33 pm

The PCjr lives again... I'll post my solution in case someone else has this issue.

I couldnt find 360K images anyware... but i did find a 1.44image of IBM-PC dos 3.30.

I downloaded that to my ibm t20 linux laptop. dd'ed the image to a floppy

Then booted that on my 386 FreeDos machine. It has a 1.2M floppy drive so 360K disks are not very reliable from this machine...

The format b: /s to a 360K floppy. Copied format, sys, etc.. to this floppy..

Then booted the PCJr.

format b: /s to make a reliable 360K disk. Then spent about 10mins swaping disks back and forth to get all the files on the final boot floppy.

The PCJr's back in action.. for what? I duno yet :lol:
Cralt
 
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Re: New PCjr user

Postby Brutman » Wed Jan 20, 2010 9:24 am

I've not had too many problems with 1.2MB drives reading and writing 360KB disks. It can be an issue, but it depends on head alignment and drive quality.

Make sure you keep a few boot disks on hand. You never know when you need to reach for a backup because your primary has a problem. I have at least 30 boot disks with varying device drivers on them and DOS levels.

All you need is a 128K sidecar. They show up on eBay once in a while for not a lot of money. If you can get two of them, or a single 512K sidecar you are set.


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