• Please review our updated Terms and Rules here

Any interest in a PCjr CPU upgrade board?

PCBWay has been a bit slow due to holidays and demand for their services, so I'm still waiting for the five boards I ordered two months ago! I have them assemble the boards so this adds to the delay.

Please send me a PM if you would like a copy of the board. Im sorry I did not see the requests in this forum thread at the time I made the last order!

The MCL86jr is open sourced on GitHub, so the schematics, PCB files, FPGA source, and binary are all available, however I appreciate that people would prefer it sold assembled, programmed, and tested rather than building it on their own. I will make a larger batch next time, so please send me a PM so I can keep track, or reach out to me through MicroCoreLabs.com.

Regarding the Tandy without DMA... I dont have a system to test it on but I do support the necessary signals (as least I believe I do), so it should probably work. I have also never tried the MCL8jr in a system running faster than 4.77Mhz, so Im not sure if this would be an issue. I dont see why not, but I wouldn't want anyone to purchase one only to find out it doesn't work!
 
Do you think it would be possible to do something like a SBC on a sidecar that only uses the PCJr to pass it's signals to the peripherals attached to it?
 
animekenji said:
Do you think it would be possible to do something like a SBC on a sidecar that only uses the PCJr to pass it's signals to the peripherals attached to it?
Click to expand...

So you're saying use some other CPU/SBC to directly access the computer's peripherals as-is it was the 8088? Neat idea!

This may be possible with a new project idea I am toying around with: http://www.vcfed.org/forum/showthread.php?79524-Motherboard-debugger

Rather than just use the Teensy's CPU to run a test program it could be used to simply control the computer as the 8088 would!
 
MicroCoreLabs said:
Regarding the Tandy without DMA... I dont have a system to test it on but I do support the necessary signals (as least I believe I do), so it should probably work. I have also never tried the MCL8jr in a system running faster than 4.77Mhz, so Im not sure if this would be an issue. I dont see why not, but I wouldn't want anyone to purchase one only to find out it doesn't work!
Click to expand...

The Tandy 1000 has an upside-down memory map compared to the PCjr, so unless your device accommodates that it's not going to work "properly" in a 1000. (The 1000 requires expansion memory to be placed starting at 00000h; it counts up from zero in 128k pages up to either 512k or 384k, depending on whether we're talking about an original 1000/1000A or a 1000EX/HX, and then maps its own 128k/256k built-in memory at the end under the 640k mark. If you put 512k of RAM set up for a PCjr into one, IE, starting at 20000h, it's not going to bother counting it because it'll see no memory at 00000h and assume that's where the built-in RAM, which for the initial phase of POST is paged up to Bxxxxh, needs to go.) I'm sure moving the RAM block would be a trivial change given this is an FPGA, but it'd need to be done.
 
animekenji said:
Do you think it would be possible to do something like a SBC on a sidecar that only uses the PCJr to pass it's signals to the peripherals attached to it?
Click to expand...
You could, in theory, with a side-car to ISA adapter, plug in a ISA SBC, pull out the 8088 and built-in RAM and disable video to not conflict with the SBC and treat the whole PCjr as a ISA peripheral
 
psergiu said:
You could, in theory, with a side-car to ISA adapter, plug in a ISA SBC, pull out the 8088 and built-in RAM and disable video to not conflict with the SBC and treat the whole PCjr as a ISA peripheral
Click to expand...

I still think it's easier just to replace the 8088 with the SBC. Then you have access to everything.
 
VERAULT said:
Yes this project seems to ne a dead end unless its made opensource or sold as a kit.
Click to expand...

It's a dead end unless it's sold as a fully assembled product. Not many people can, or care to, have to assemble it themselves. I always hate it when someone creates something amazing, and then will only sell you plans or a parts kit.
 
animekenji said:
It's a dead end unless it's sold as a fully assembled product. Not many people can, or care to, have to assemble it themselves. I always hate it when someone creates something amazing, and then will only sell you plans or a parts kit.
Click to expand...

I agree that nobody wants projects like this in kit form. :)

I just received word that the five boards I had built are finished and will be shipped by PCBWay this week. I will reach out to the folks who requested one once they are programmed and tested.

Hopefully these five boards are enough for the current interest, but if anyone else wants one, please PM me and I will kick off another build.
 
MicroCoreLabs said:
I agree that nobody wants projects like this in kit form. :)

I just received word that the five boards I had built are finished and will be shipped by PCBWay this week. I will reach out to the folks who requested one once they are programmed and tested.

Hopefully these five boards are enough for the current interest, but if anyone else wants one, please PM me and I will kick off another build.
Click to expand...

I didn't say that "nobody" would want it. What I'm saying is that you severely limit your market when you do it that way because many people who might otherwise buy it in pre-assembled form, won't buy it as a kit or a blueprint if they don't have the time or the skill to assemble it themselves. If they are pre-assembled, they would be willing to pay the extra for the convenience of it being plug in and go.
 
animekenji said:
I didn't say that "nobody" would want it. What I'm saying is that you severely limit your market when you do it that way because many people who might otherwise buy it in pre-assembled form, won't buy it as a kit or a blueprint if they don't have the time or the skill to assemble it themselves. If they are pre-assembled, they would be willing to pay the extra for the convenience of it being plug in and go.
Click to expand...

Tooling up for a production run of a hobby project sizable enough to make profit even relevant is a massive undertaking. You clearly don't understand that. Thinking about "limiting" one's market when the product itself is this niche is somewhat comical. You should be grateful that anyone even cares enough about this stuff to design these projects. Expecting them to cater to your convenience sounds reasonable when you talk about being willing to pay for it, but the reality is that on super short runs the amount they would have to charge to truly compensate themselves fairly for the time invested in setting up the production would be astronomical.
 
maxtherabbit said:
Tooling up for a production run of a hobby project sizable enough to make profit even relevant is a massive undertaking. You clearly don't understand that. Thinking about "limiting" one's market when the product itself is this niche is somewhat comical. You should be grateful that anyone even cares enough about this stuff to design these projects. Expecting them to cater to your convenience sounds reasonable when you talk about being willing to pay for it, but the reality is that on super short runs the amount they would have to charge to truly compensate themselves fairly for the time invested in setting up the production would be astronomical.
Click to expand...

Then it's not worth the time that goes into designing it, either, if only 5 people are going to buy it.
 
animekenji said:
Then it's not worth the time that goes into designing it, either, if only 5 people are going to buy it.
Click to expand...

that would be true if the purpose behind designing it was to create a product for sale

you are (intentionally?) missing the fact that most of these cottage designs are made for the benefit of the designer out of love for the hobby
 
I have listed the next batch of five MCL86jr boards on Ebay: https://www.ebay.com/itm/154425005735

I listed them for $1,000 so VCF members could get the first shot at them before someone else gets them.

If you offer $90 then I will accept!

Thanks!
​​​​​​​-Ted
 
MicroCoreLabs said:
I have listed the next batch of five MCL86jr boards on Ebay: https://www.ebay.com/itm/154425005735

I listed them for $1,000 so VCF members could get the first shot at them before someone else gets them.

If you offer $90 then I will accept!

Thanks!
​​​​​​​-Ted
Click to expand...

Man, I wish something like this were available for my Tandy 1000 EX and HX systems. I've upgraded them to V20 but this would be way better!
 
Well, it is available in a sense. All of the project files are on GitHub, so someone could easily port this design to support the Tandy. My understanding is that the differences are just in a mapping of expanded memory which is slightly different than the IBM XT.

I wish I could build a board to support the Tandy, but there are just so many projects I can tackle at a time! :)
 
I'm just discovering this thread, very nice project! I may be interested in trying to adapt the design to the Tandy. Just got an EX that I have been looking forward to playing with. Also have a bunch of ice40 fpgas I use for another project - although they definitely don't have enough RAM for 512k. Maybe I can use two of them.. in any case that will be added to the project queue.
 
The Spartan-6 I'm using doesn't have enough RAM either! So I'm using an external 512Kx8 SRAM. :)
 
You must log in or register to reply here.
Back
Top