Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!purdue!haven!udel!udccvax1!mikej
From: mikej@vax1.acs.udel.EDU (Michael Jacobs)
Newsgroups: comp.sys.ibm.pc
Subject: Re: PCjr expanded memory
Keywords: memory side-car
Message-ID: <4326@udccvax1.acs.udel.EDU>
Date: 9 Sep 89 20:47:34 GMT
References: <10106@bsu-cs.bsu.edu>
Reply-To: mikej@vax1.acs.udel.EDU (Michael Jacobs)
Organization: University of Delaware
Lines: 28

>  I recently acquired a used 128k memory side car for my jr, boosting
>it to a whopping 256k machine. My question is, does anyone have any
>documentation on what parameters there are and what they are for
>that go along with configjr.sys?
>device = configjr.sys -X -Y -Z

I use a program call jrconfig.  Is that what you meant?
If it is, say so, and I'll tell you what the options are.

>Also, is the extra memory only found if i boot from dos with the above in
>my config.sys?  what if i want to run a program that requires more than
>the original 128k but to run it I just put it in the drive and boot the 
>machine? will it know that i have 256k or will it think i have only 128k?

What IBM did to the jr was to have all the low-end and dos stuff at the
bottom of memory, then active program memory, then the screen memory on
top.  What these memory driver programs to is put the screen memory next
to the dos memory, so memory for programs can go all the way to the 640k
top.  If you don't use one, you'll have a whopping 64k of memory to
use for programs regardless of what sidecars you have attached.

>Since the side-car expansion and the optional parallel port can be "snapped"
>together, i assume that if I knew which of the pins were for the parallel
>port, i wouldn't need to spend the money to buy the add-on port. I could
>probably come up with something on my own?

In theory, yes.  The PCjr technical reference manual probably has the
details you need.