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How to create a 512K PCJR sidecar from 128k

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Chromedome45

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Title pretty much says it all. What are the steps to hacking a 128k sidecar to be a 512k besides changing chips to 256k bit? Any help as always apprecited. And BTW I am not afraid of cutting and soldering! ;) Oh how the heck do you open the sidecar anyway?
 
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I modified a Tecmar jr Captain from 128K to 512K way back in 1985. Unsoldered all the memory chips with
a solder sucker and put sockets in. I think it may depend on which type sidecar you have, for the Tecmar
card it was just replacing the memory chips. The Tecmar card had a snap in plastic cover on the outside
that just popped out, then remove some screws holding the circuit board in. It's weird how I remember
all that ....... :)
 
I got it opened up but looking at the 64k RAM chips specifically pin 1 I don't see that there is a trace going anywhere. So if I put in 256k chips I'll have to wire up pin 1 on all 16 chips to A9. Trick is finding A9! Wish I had a schematic for the mem sidecar.
 
I'm certain there's a document floating around that has instructions for the modification.
I take it you have the genuine IBM 128K sidecar ? Send a PM to mbrutman , he is the PCjr
guru around here, he may have the instructions.
 
mikey99 said:
I modified a Tecmar jr Captain from 128K to 512K way back in 1985. Unsoldered all the memory chips with a solder sucker and put sockets in. I think it may depend on which type sidecar you have, for the Tecmarcard it was just replacing the memory chips.
Click to expand...

Now that's cool, considering that I'm using a Jr Captain on mine (I also have the official IBM one). So there's no cutting traces and re-routing for the memory address lines for this one? That seems... strange. But I'd be willing to try :) I'd love to modify the parallel port to a bidirectional one as well. Make my Jr much more usable.
 
Hey Mav, Just remember to remove chips like I showed you. BTW Skycraft has a bunch of 256k Ram chips! You'll see when we go there on Saturday. Or I could do it for you!
 
OK... We found the documents for performing this mod around on some old FTP sites, Frank's performed it on his 128k sidecar, and it works great!

but I'm curious... and hopefully the asking isn't taboo here (I'll leave that up to the mods)...

Why isn't this information freely found around on different websites - why does it seem to be hidden in old FTP archives? All of the other PCjr mods seem to be easily found - the Tandy 1000 sound mod, the parallel port mod, etc - just the memory mod seemed to be on no sites - at least not with any detail.
 
Stick it in the wiki on here... or PM me with it and I'll put it up on my blog.
 
I don't think that you have stumbled into something secret ... just obscure.

Most Jr owners already have 512 or 640K, and they did it years ago. Directions for modifying IBM and Microsoft booster sidecars have been floating around in paper form for years, and I know I've scanned them and sent them out before. Tecmar's are a little more esoteric - their JrCaptain and JrCadet setup was strange. A lot of people have a jrHotshot or equivalent, and if you have a Racore you probably have 512K already. You are probably the first person to do a sidecar upgrade in a the last few years.

And normally I would have provided the scans of what you need, but I have been preoccupied elsewhere. I don't have this stuff posted on my web site in public because I generally like to do a procedure myself before I have other people do it. (Notice the detail on the parallel port modifications.)

Over at the PCjr forum (http://www.brutman.com/forums) we are discussing options for putting XT-IDE on the Jr. That thread includes discussing adding a 512KB and a 128KB SRAM so that we can do the 736K upgrade in the same sidecar/expansion card. Ethernet is a possibility too. There is another thread where one of the newer members is working out the prototype for a 512KB internal expansion daughterboard.


Mike
 
Great, can you please post a link here to the documents and ftp site ? I'm interested in looking at those :)
Might be some other good stuff on those ftp sites too.
Thanks.

Maverick1978 said:
OK... We found the documents for performing this mod around on some old FTP sites, Frank's performed it on his 128k sidecar, and it works great!.....
Click to expand...
 
Mikey, make sure to use the Find feature in your browser to look for "jr" - there are a lot of other PCjr-related documents on that FTP mirror as well.

mbbrutman said:
I don't think that you have stumbled into something secret ... just obscure.

And normally I would have provided the scans of what you need, but I have been preoccupied elsewhere. I don't have this stuff posted on my web site in public because I generally like to do a procedure myself before I have other people do it. (Notice the detail on the parallel port modifications.)
Click to expand...

That explains it - I had seen a post or two over the years about all things were posted that could legally be posted, etc - but I never saw anything further. Was curious if there was something further, or it it was simply because the Jr is unpopular and those that use them already have all the mods installed, etc.

The docs that Frank and I found were old-school ascii files with the ascii drawing characters for the cards. I would personally love to see an html re-write with real pictures of the mods, if for no other reason than for historical purposes. Something to think about when I get around to modifying my own IBM sidecar (or TecMar JrCaptain, assuming I can find specific info for that memory mod and bidirectional parallel mod)
 
I presume you have seen the bi-directional modification for the IBM parallel port sidecar. You should be able to use the write-up and diagrams to do something similar with the jrCaptain parallel port. There are only so many ways to implement a parallel port, and they are going to have a similar schematic as the IBM ones.

The scanned versions of the modifications are a little better, but nothing like the detail I put into the bi-directional and LPT2 modification write-ups.
 
mbbrutman said:
Directions for modifying IBM and Microsoft booster sidecars have been floating around in paper form for years, and I know I've scanned them and sent them out before.
Click to expand...

Do have the one for the MS Booster lying around to send me by any chance?
 
resurrecting an old thread for future visitors...
I somehow got lost in the depths that are cd.textfiles.com and found myself here:

http://cdmirror.textfiles.com/hof91/pcjr/

which has a huge amount of jr info, including the file ms_upgd.lzh which explains how to boost the MS booster to 640k.
Yay for LZH files. ah the memories!
 
Nice find, thanks for the post!

I've decided to hold off on modifying my 128kb sidecar to 512kb, as I managed to get a Racore expansion with a parallel, RTC, memory, and 2nd floppy drive.

Still wouldn't mind getting the parallel to be bidirectional so I could pop on my Xircom ethernet adapter.

There's just never enough time in the day... :)
 
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