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This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

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There are several hundred people who actively participate here. People come from all different backgrounds and will have different ways of seeing things. You will not agree with everything you read here. Back-and-forth discussions are fine but do not cross the line into rude or disrespectful behavior.

Conduct yourself as you would at any other place where people come together in person to discuss their hobby. If you wouldn't say something to somebody in person, then you probably should not be writing it here.

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To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
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Why do we have this policy? Sending a "PM Sent!" type message basically wastes everybody else's time by making them having to scroll past a post in a thread that looks to be updated, when the update is not meaningful. And the person you are sending the PM to will be notified by the forum software that they have a message waiting for them. Look up at the top near the right edge where it says 'Notifications' ... if you have a PM waiting, it will tell you there.

Rule 5: Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

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New user moderation

New users are directly moderated so that we can weed spammers out early. This means that for your first 10 posts you will have some delay before they are seen. We understand this can be disruptive to the flow of conversation and we try to keep up with our new user moderation duties to avoid undue inconvenience. Please do not make duplicate posts, extra posts to bump your post count, or ask the moderators to expedite this process; 10 moderated posts will go by quickly.

New users also have a smaller personal message inbox limit and are rate limited when sending PMs to other users.


Other suggestions
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Any interest in a PCjr CPU upgrade board?

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    #61
    Will this work in Tandy systems that don't have DMA?

    Comment


      #62
      Yes this project seems to ne a dead end unless its made opensource or sold as a kit.

      Comment


        #63
        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!

        Comment


          #64
          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?

          Comment


            #65
            Originally posted by animekenji View Post
            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?
            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/showthrea...board-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!

            Comment


              #66
              Originally posted by MicroCoreLabs View Post
              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!
              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.
              My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

              Comment


                #67
                Originally posted by animekenji View Post
                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?
                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

                Comment


                  #68
                  Originally posted by psergiu View Post
                  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
                  I still think it's easier just to replace the 8088 with the SBC. Then you have access to everything.

                  Comment


                    #69
                    Originally posted by VERAULT View Post
                    Yes this project seems to ne a dead end unless its made opensource or sold as a kit.
                    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.

                    Comment


                      #70
                      Originally posted by animekenji View Post
                      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.
                      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.

                      Comment


                        #71
                        Originally posted by MicroCoreLabs View Post
                        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.
                        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.

                        Comment


                          #72
                          Originally posted by animekenji View Post
                          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.
                          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.

                          Comment


                            #73
                            Originally posted by maxtherabbit View Post
                            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.
                            Then it's not worth the time that goes into designing it, either, if only 5 people are going to buy it.

                            Comment


                              #74
                              Originally posted by animekenji View Post
                              Then it's not worth the time that goes into designing it, either, if only 5 people are going to buy it.
                              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

                              Comment


                                #75
                                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

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