Mike's PCjr Page

can you post a picture or screen shot...

geoffdaddy wrote:I am wondering if anyone else has problems with their mod on some PCjr programs. Notably, I have noticed that Colorpaint doesn't display properly on my jr with the mod performed. Of course, there could always be an issue with the mod I did, but it seems that most everything else I've tried with it works.

ScubaVenture has an issue where a solid line encroaches on the river with the Tandy mod installed and Mouser has a minor flickering line on top of the screen, but Mouser's line does not affect gameplay.

Colorpaint is one of the rare programs that uses PCjr's 640x200x4 mode which accesses memory differently than 320x200x16 mode. Page 2-60 of the technical reference shows the memory layout in this mode. It's possible the common Tandy mod doesn't work with this, which is why Alan's design of being able to switch it off is a good idea.

I ordered a couple chips to program with Alans code.
as with most of us Alan is pretty busy, so I thought I would try to get a few boards built up and test on a couple systems I am playing with.
I will layout the pcb and have some boards made, so it will take a few weeks to get this done.
I am going to add a two pin header that can subsitute as ‘jumper’ like those on the floppy/harddrives etc.
This was you can make a switch cable and run it to the back of the computer for selectin on and off easily.

If anyone else has an interest in these let me know.

thanks to Alan for documenting this mod for the Jr folks....

To Alan: I have read the docs on the PAL but was confused as to the TandyMod+
and the board design, could not wrap around how it applies to the add-on board...

I am missing a key point here I am sure..
‘Chuck

A quick update ( I know I'm the only one posting on here lately, but it's now my personal journal (grin) ):

I had gotten 3 TandyMod boards from Alan and they were extremely well done.....
I modified a platform with socket and gave it a go.....
I ran KQ3 from original 5.25 Floppy (original game floppies, not copies)
JRConfig /v32 set !
It came up with the Venetian 'blinds' interlacing issue...

Tried boards 2 and 3 and both gave the same results....

Just had a thought, has anyone had a Mother Board that would not work with the tandymod ?

I can try the mod on another MB but hate to go thru all that work to see the Blinds again....

Updated: Tried Battle Chess still have the Blinds...

chuck

Use /v64 and see if that helps. It probably won't, but it reserves enough video memory for two full 320x200x16 video pages (which is what I use all the time, just in case).

All motherboards are the same; there was only one PCjr motherboard. I'd contact alan and see if he can help you troubleshoot what's going on, maybe send one back to him to have him verify on his hardware.

Thanks Jim...I will try the v64 ' can't hurt "
and actually I reprogrammed one of the pals on Alans boards just to ensure it was programmed properly...
so I think his boards are good...but I may send him one to try...

****** SOLVED ******

This was a bit of a journey, but well spent time as it allowed me to review a lot of the Jr aspects after 12 yrs..

As I mentioned I had gotten new TandyMod boards from Alan , the TandyMod with the 16LV8 PALs ,a very nice solution...

Tonight I stuck a 7486 chipon the mother board after not getting Alan’s to work , the venitian blind issue...

well after trying it with the hardwired chip, nope, still had issues.

I had suspected now for a week it could be a configuration issue, and tonight I was correct!
In the JRCONFIG line I had the typical /v32 specified, but I also had the /s0 executing.
I read the JRconfig manual very intensively tonight and there was a paragraph that specifically mentions the tandymod will not work with the /s giving room for slow Ram.

My config was putting 48k in Slow memory, and after I removed that command on the line, all was fine, was able to start Bards Tale with no issues.

I went back installed Alans board an it also worked great.

So I will call this thread complete.

it seems this is an important part of getting the TandyMod to work, but it was only briefly mentioned in the JRconfig manual.
I hope this thread sheds a little more light for new folks that may fall into this same newbee trap.

thanks to Alan and Jim for the ideas and help..
as usual. I had fun.....

chuck

Just out of curiosity, are these mod boards available for sale anywhere?

Not really. I never intended to build them for sale. However I 'think' I have the parts for a few more. I need to check. I'll reply here probably tomorrow (Sunday Dec 9) if I have enough for a few more.

The TandyMOD+ replaces ZM31 with a small carrier board with a SMT 16v8. It does require you to desolder the original ZM31 chip (a LS157 as I recall) from the PCJr main board. It is not a socketed chip.

Oddly just this week, I've worked out a similar board for a ZM56 chip replacement (originally a 1K x 4 bit ROM). It controls which 32KB sections of memory are serviced by the main board and which are gated to the side-car / also which CPU addresses map to the 128KB system RAM via the VGA (Video Gate Array). It has 4 switches. 2 control whether segment 0 and 1 respectively get mapped to 128KB on-board or side-car. And 2 control whether segment D and E respectively get mapped to cartridge slots or side-car.

The later is more interesting because a stock JR-IDE can fill segments D/E with RAM (and the remainder of C). It could be used for a 176 KB RAM disk or upcoming UMB support in JR-IDE BIOS.

Segments 0/1 brings about an interesting experiment.... Direct 0/1 to side-car, rewrite JR-IDE CPLD to fill 0/1 with card memory, get rid of JRCONFIG.SYS entirely, enable TandyMOD+ to fix the BC000 aliasing problem, run TSOUND to switch the speaker mux to the Tandy sound chip, and then change machine code in the system ROM to match that of a Tandy 1000. I believe, at that point, you'd almost have a perfectly hardware compatible Tandy 1000. Why? I don't know. Just get a Tandy 1000. It's a better machine with ISA slots. But it would be an 'interesting' test case.