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Tecmar jrWave Memory Expansion for the IBM PCjr (pics)

M

misterblack

Experienced Member
Joined
Jul 20, 2017
Messages
228
Location
Portland, Oregon, USA
Hey guys -- a viewer sent me a very nice memory sidecar for my PCjr. He sent a Tecmar jrWave expansion sidecar.

Pics and some info:
https://imgur.com/a/m5uee6M

He wasn't sure if it worked at all as he had had it a long time and no longer has a PCjr. He also didn't have the manuals or power supply for the board.

Taking it apart, I found the AC input is rectified and converted to 5v by a simple 7805 voltage regulator. I fed the board with 5v from the PicoATX that runs my PCjr to power up the board. This board is populated with two banks of 8 by 256k RAM chips (total of 512k) and then two banks of 8 x 64k chips (for a total of 128k in these banks) bringing it to a total of 640k on the sidecar.

Upon power-up, it wasn't working correctly with the PCjr either counting to 160k then giving an "ERROR A" or it just wouldn't count RAM at all. I fiddled with the board a little and pushed the chips down and suddenly it's counting to 640k and seemingly working normally.

I was wondering if anyone knew anything about this board? Is 640k the max capacity of it? I can't find any scans of the manual for it. It seems to have the expansion connector on it for the jrCadet (expansion board) but reading the manual for the jrCaptain, that was only populated with banks of 64k RAM.

The switch settings for the 640k configuration are like this:

1234
COOO

(C = closed, O = open as marked on my switch block. These are rocker switches so switch 1 is down, others are up)

12345678
11111111
(1 = ON, 0 = off -- so essentially this block is entirely ON. All switches down)
 
Very cool find. Can't help with a manual, but here's a nice article from PC Tech Journal which I happened to bump into earlier today: https://archive.org/details/PC_Tech_Journal_vol03_n02/page/n57
According to that, 640K is indeed the maximum configuration.

Did this come with any software? The article mentions a set of 24 programs that comes with the jrCaptain (another Tecmar sidecar), but nothing about the jrWave, so I wonder if that one was bundled with anything. Hopefully, at least the jrCaptain software has been preserved somewhere...
 
misterblack said:
Hey guys -- a viewer sent me a very nice memory sidecar for my PCjr. He sent a Tecmar jrWave expansion sidecar.
Click to expand...

You can mention me by by forum name you know, after all I do sort of live over here. :D

Glad to see you are getting a bit further with it then I did. I just never found much in the way if info or setting on the thing, though I never touched the settings on the thing, so they are as I got it too. O, and FYI The jr can support up to 768kb of RAM, so the jrWave is designed to give you that much (hence the 640kb on it).
 
VileR said:
Did this come with any software? The article mentions a set of 24 programs that comes with the jrCaptain (another Tecmar sidecar), but nothing about the jrWave, so I wonder if that one was bundled with anything. Hopefully, at least the jrCaptain software has been preserved somewhere...
Click to expand...

Alas, all I had was the board it'self. From what I could gather the only difference between the jrWave and jrCaptain was the the Wave was just memory (upto 640Kb) whereas the Captain was memory (upto 512kb), RTC and parallel port. I believe both would work with the jrCadet (also a RAM expansion option, but I think it was internal rather than a sidecare though I could be wrong).
 
lutiana said:
You can mention me by by forum name you know, after all I do sort of live over here. :D

Glad to see you are getting a bit further with it then I did. I just never found much in the way if info or setting on the thing, though I never touched the settings on the thing, so they are as I got it too. O, and FYI The jr can support up to 768kb of RAM, so the jrWave is designed to give you that much (hence the 640kb on it).
Click to expand...

LOL! Some people want to remain anonymous :) But yes, pleased it is working, at least sort-of. I tried using the JRCONFIG.SYS and it does seem to work but once the memory is allocated to DOS, things start acting a little funny. Sometimes "memory allocation errors" in DOS or spontaneous reboots. I just grabbed the Tecmar utilities, so let's see if those work a bit more reliably. I just need to go through every chip and reseat them as that seemed to be the cause of my initial issues.

This is it running JRCONFIG.SYS:
IMG_20181226_155103.jpg

I did get mips.com running and since it was running in the "fast" ram on the jrWave, it was running at full PC-XT speed.
IMG_20181226_160141.jpg

Nice!
 
lutiana said:
Alas, all I had was the board it'self. From what I could gather the only difference between the jrWave and jrCaptain was the the Wave was just memory (upto 640Kb) whereas the Captain was memory (upto 512kb), RTC and parallel port. I believe both would work with the jrCadet (also a RAM expansion option, but I think it was internal rather than a sidecare though I could be wrong).
Click to expand...

The jrCadet is a sidecar with a max of 384Kb, it differs from the jrWave & jrCaptain as it doesnt have the ability to use 256 Kb chips according to a Tecmar ad I found (unless someone know otherwise).

I know the jrCaptain has a jumper in it you need to set if you populate it with 256Kb chips instead of 64Kb ones.

At least your thread on the jrWave has a few replies..... mine on the Tecmar Wave for the PC/XT didnt get a single response, I could find zero info on that card and what its jumpers do.
 
Gremlin5 said:
Here are some pics of my jrCadet if you are interested.
Click to expand...

Fascinating -- so yes the JrWave has that pin header to allow the JrCadet to connect up. I guess if you had a whole lot of 64k RAM chips then could buy the Cadet to keep adding RAM.

So I did a little more troubleshooting --- using the Tecmar "MEMTEST" utility, I am getting some issues with chip select lines as evidence by this picture:

IMG_20190101_180244.jpg

MEMTEST says I have 640k, and it runs through tests without issues but then gets bank selection errors:

Bank 2000h, 3000h and 4000h all actually end up at 5000h.
Bank 6000h and 7000h end up at 8000h
I assume 1000h, 5000h, 8000h and 9000h all end up at their respective banks.

So when trying to access any memory between 2000 and 2FFF you end up reading/writing to 5000-5FFF. No wonder I was getting strange crashing! This reeks of chip selection issues and I bet it may have something to do with the DIP switches. I can't rule out a logic issue or even a bad connection but still hmmm.

1->1 Binary 0001 Getting 0001
2->5 Binary 0010 Getting 0101
3->5 Binary 0011 Getting 0101
4->5 Binary 0100 Getting 0101
5->5 Binary 0101 Getting 0101
6->8 Binary 0110 Getting 1000
7->8 Binary 0111 Getting 1000
8->8 Binary 1000 Getting 1000
9->9 Binary 1001 Getting 1001

I have been fiddling with the DIP switches and after several tests at 640k (with no changes) I ended up getting the computer at 384k and then the bank selection issues were slightly different:

1 -> 1
2 -> 4
3 -> 4
4 -> 4
5 -> 5

Again banks 2 and 3 had selection issues now. Need to keep fiddling trying different combinations, but I may end up trying to reverse engineer things a little. The board has 4 or 5 GALs on it, making it very hard to troubleshoot. I suppose RAM could be bad too although so far I have not seen any RAM errors.

If anyone has input, it would be greatly appreciated. Thanks!
 
Hi guys, ok I have everything sorted out. Unfortunately, my PCjr itself or the Tecmar JrWave appears to have issues. As soon as I add memory then enable it (using either JRCONFIG.SYS or Techmar's CONPCJR) the computer becomes unstable. (More on that in a second)

My issue with the memory test failing the MEMTEST initially was due to the RAM being installed incorrectly. This is how it needs to be installed:
IMG_20190102_012956.jpg

I figured out that the 256k RAM chips need to be installed on the left part of the board and the 64k chips on the right. This is opposite of how the board was when I got it. The board is wired up to support 41256 chips in all sockets, but it only seems to support a max of 640k and if you don't have the chips in the right spot, you get that reflected memory issue.

I then tinkered enough to figure out the DIP switch configs, which may help others who have this board:
Capture.jpg

I never figured out what switch 2-8 do on the 8 switch block. They are connected to a GAL along with the others, but they seem to have zero effect on anything. Maybe they are for the JrCadet?

Sadly, the machine is just not stable with added memory. I can sometimes run some programs but inevitably it will freeze, crash or give me a DOS Memory allocation error. I tried everything I could:

  • Every Possible RAM size configuration -- the system is slightly more stable using less memory, but only a little
  • A full size ATX power supply (in case my PicoATX was causing an issue) -- no change at all
  • CONPCJR (Tecmar) and JRCONFIG.SYS -- both yield exactly the same issues
  • I'm using IBM PC DOS 2.11 (Patched) here but also tried IBM PC DOS 3.3 -- not difference either
  • All chips on the JrWave have been reseated (With Deoxit) along with the DIP switches -- I was actually having some issues with those at first with odd behavior

Anyway, at this point I guess I'm kind of at a dead end. MEMTEST runs perfectly, as does the initial boot up RAM check ... I also left it running the PCjr diags (Ctrl-Alt-Insert) for an hour (it counts up to 640k and loops) with nary an issue... but then DOS is unstable using the memory... Any thoughts would be appreciated.

Thanks!

Pics of me running the board and the errors:
https://imgur.com/a/ezMBoEI

PS: Here is the switch configuration in text form for someone in the future who doesn't have access to archived pictures:
Code: 
Reported Size	Actual Size	JrWave Mem	DIP SW 1-4	DIP SW 1-8	Banks	Chips
128	128	0	X0XX	XXXX XXXX	JrWave Disabled? (Stock)	N/A
192	192	64	1101	0XXX XXXX	One bank of 64k	4164 RAM
256	256	128	1110	0XXX XXXX	Two banks of 64k	4164 RAM
320	320	192	1111	0XXX XXXX	Three banks of 64k	4164 RAM
384	384	256	1111	1XXX XXXX	Four banks of 64k	4164 RAM
384	384	256	0101	0XXX XXXX	One bank of 256k	41256 RAM
640	640	512	0110	0XXX XXXX	Two banks of 256k	41256 RAM
640	704	576	0111	0XXX XXXX	Two banks of 256k and one bank of 64k	41256 + 4164 RAM
640	768	640	0111	1XXX XXXX	Two banks of 256k and two banks of 64k	41256 + 4164 RAM
 
Not a helpful reply...but I didn't know you were on this forum. Just chiming in to say I'm a big fan of your channel! Keep up the great work.
 
Well I'm calling it quits on this card .... I don't know how many hours I've spent testing this but there is something wrong with the DRAM fresh on it. Over time the RAM on the JrWave starts to lose the contents and if you try to use the RAM, it will crash. I outlined what happens in the post above and I don't see a way to fix this. The refresh is controlled by the PALs based on the CPU clock, but something must be wrong

At least I figure out the DRAM bank layout and the DIP switches -- so I'm posting that here in case anyone in the future needs it. (It's the stupidest layout I have ever seen -- no idea what they were thinking.)

RAM Bank Layout and DIP Switch Configuration.jpg

And Imgur link for those who may not have an account:
https://imgur.com/gallery/sAesYQk

If anyone has a thought of what's wrong, I'm all ears.... but I think it's time to move on and give up on the PCjr (For now at least.)
 
Have you tried using an external power supply for +5 V to the jrWave ?
With the original jrWave power supply, the sidecar receives power before
the system unit is powered on. Maybe powering on the system unit and
sidecar at the same time is creating some issues.
 
Did you ever check all the traces and such on that sidecar? I think mbbrutman said over on his PCJr forum that some of the different sidecars tend to get over tightened and that can flex the cards and play hell with the traces and such cause some cards to become quite flackey, you did say something about flexing the card and getting it working.

Beyond that I dont have any ideas, I have one PCJr running with a 512kb Tecmar JR Captain and another one running with a 128KB Tecmar JR Captain w/ 384kb JR Cadet and neither of those have gave me any problems or wonky memory problems as far as I know. I haven't tested everything so {shrug}.
 
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