Announcement

Collapse

Forum Rules and Etiquette

Our mission ...

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.

This forum has been around in this format for over 15 years. These rules and guidelines help us maintain a healthy and active community, and we moderate the forum to keep things on track. Please familiarize yourself with these rules and guidelines.


Rule 1: Remain civil and respectful

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.

This should be obvious but, just in case: profanity, threats, slurs against any group (sexual, racial, gender, etc.) will not be tolerated.


Rule 2: Stay close to the original topic being discussed
  • If you are starting a new thread choose a reasonable sub-forum to start your thread. (If you choose incorrectly don't worry, we can fix that.)
  • If you are responding to a thread, stay on topic - the original poster was trying to achieve something. You can always start a new thread instead of potentially "hijacking" an existing thread.



Rule 3: Contribute something meaningful

To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
  • This is not a chat room. If you are taking less than 30 seconds to make a post then you are probably doing something wrong. A post should be on topic, clear, and contribute something meaningful to the discussion. If people read your posts and feel that their time as been wasted, they will stop reading your posts. Worse yet, they will stop visiting and we'll lose their experience and contributions.
  • Do not bump threads.
  • Do not "necro-post" unless you are following up to a specific person on a specific thread. And even then, that person may have moved on. Just start a new thread for your related topic.
  • Use the Private Message system for posts that are targeted at a specific person.


Rule 4: "PM Sent!" messages (or, how to use the Private Message system)

This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

In short, if you are going to reply to a thread and that reply is targeted to a specific individual and not of interest to anybody else (either now or in the future) then send a private message instead.

Here are some obvious examples of when you should not reply to a thread and use the PM system instead:
  • "PM Sent!": Do not tell the rest of us that you sent a PM ... the forum software will tell the other person that they have a PM waiting.
  • "How much is shipping to ....": This is a very specific and directed question that is not of interest to anybody else.


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.

Our discussions here generally fall under "fair use." Telling people how to pirate a software title is an example of something that is not allowable here.


Reporting problematic posts

If you see spam, a wildly off-topic post, or something abusive or illegal please report the thread by clicking on the "Report Post" icon. (It looks like an exclamation point in a triangle and it is available under every post.) This send a notification to all of the moderators, so somebody will see it and deal with it.

If you are unsure you may consider sending a private message to a moderator instead.


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
  • Use Google, books, or other definitive sources. There is a lot of information out there.
  • Don't make people guess at what you are trying to say; we are not mind readers. Be clear and concise.
  • Spelling and grammar are not rated, but they do make a post easier to read.
See more
See less

XT-FDC project level of interest

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    #76
    You can buy floppy emulators that take memory cards already (been around for ages), they just connect as a normal 1.44 floppy drive would.

    HD 8 bit controller with BIOS and four drives - awesome

    Edit: donated $US30 to assist with prototypes
    Last edited by SpidersWeb; September 4, 2012, 01:37 PM.
    Twitter / YouTube

    Comment


      #77
      Ya', but they're either USB devices, made for sewing or embroidery equipment, keyboards, or cost hundreds. I've yet to see a cheapo for a DOS PC.
      PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

      Comment


        #78
        I think USB would be more handy
        http://www.ebay.com/itm/3-5-1-44MB-U...item35bf4bc9b3
        I'll have to order one and test to confirm, but it's advertised as standard AT interface 34 pin that emulates a 1.44Mb drive and costs under $30.

        Sorry to OP for the off topic, just wanted to mention that little solution.
        Twitter / YouTube

        Comment


          #79
          Yes, but how do you run a USB drive on a DOS PC, XT or AT?
          PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

          Comment


            #80
            Originally posted by Stone View Post
            Yes, but how do you run a USB drive on a DOS PC, XT or AT?
            You should click his link.

            I promise there is no Rick Astley behind it.
            "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

            Comment


              #81
              Originally posted by MikeS View Post
              $160 for 4 boards??? How big are they? How many layers? Sounds kinda steep...
              Hi Mike
              They are standard 2-layer PCBs from www.33each.com and are top-notch prototype boards. They are an excellent value and can be up to 60 square inches of any shape. Very nice and well worth it. I highly recommend them.

              Thanks and have a nice day!

              Andrew Lynch

              Comment


                #82
                For that shape and size 40 a pop is quite cheap for a proto.
                If i am given a Gerber file i could mill it myself which would result in a lower quality proto board and i have to stamp the via's in by hand hence my comment to go easy on the via's.

                So that would raise the total proto board to 5 Besides that i am sure Andrew still has a ace up his sleeve.

                Comment


                  #83
                  Given that this is all through-hole, it'd be simple enough to wire-wrap up a prototype. I realize that this isn't the way it's done today, but I still do mine that way.
                  Reach me: vcfblackhole _at_ protonmail dot com.

                  Comment


                    #84
                    Hi! Good news! Some additional prototype board donations came in and we are now up to $130! Woo Hoo! Almost there!

                    The current design has about 90 vias and 552 pads. If you are planning to hand drill and plug those vias it is going to be some serious work!

                    Chuck and I are still going back and forth on the design. The main issue remaining is what to do capture configuration information.

                    I think we are getting close though. More updates as they come available!

                    Thanks and have a nice day!

                    Andrew Lynch

                    Comment


                      #85
                      Originally posted by lynchaj View Post
                      Hi Mike
                      They are standard 2-layer PCBs from www.33each.com and are top-notch prototype boards. They are an excellent value and can be up to 60 square inches of any shape. Very nice and well worth it. I highly recommend them.

                      Andrew Lynch
                      Looks like you've pretty well covered it anyway.

                      But you might try this prototype service one day:
                      http://oshpark.com/pricing
                      3 copies of a half-length ISA board would cost abt. $75.00 incl. shipping; silk-screen & solder mask both sides, gold coated.
                      Larger quantities $1.00 per sq. inch

                      Comment


                        #86
                        Originally posted by lynchaj View Post
                        Hi
                        That's a neat idea but I wouldn't want to mess up the XT-IDE by combining it with a floppy controller. I guess I've adopted John Monahan's philosophy of one function per board. It makes for a much simpler design and a *lot* easier to debug. Also I think there would less interest in a combination board rather than a single function boards.

                        Thanks and have a nice day!

                        Andrew Lynch
                        Multifunction is the way to go once you get the single function card working correctly, you wouldn't want 5 computers performing single tasks would you?
                        GEEKS WITH A GRUDGE!

                        Comment


                          #87
                          Function/feature != tasks

                          Comment


                            #88
                            Originally posted by lucasdaytona View Post
                            Hey Andrew, it's possible to have an emergency boot disk image on ROM in this board? A backup free dos with minimal disk utility, with an option to boot using a menu like the one in XT-IDE, this would be very handy. I think there's space to do this with a 27512, and the costs won't be in sky, just an idea, of course.
                            Hi Lucas,
                            We've made some progress on the storing of configuration information on the XT-FDC design. We can put the information in the same EEPROM as the BIOS and it can be write protected to keep it from being overwritten. The good news about it is it frees up what used to be an input port for switches now can be reused as an output port for ROM upper address lines. I think it makes the larger ROM idea a lot more feasible and so I'd like to revisit this concept.

                            I'd suggest a dual memory approach. The BIOS and configuration information would be stored in a 28C64 with write protect. This is part of the design already and is required if you want to use the XT-FDC to boot using its BIOS. It is basically reused from the original XT-IDE design and pretty reliable. It is still "optional" if you don't care about the FDC BIOS or config information and just want FDC. It has to be simple, reliable and stay in memory at all times (no switching memory context with a latch or it will crash the CPU if running code in the BIOS ROM).

                            For the Flash ROM drive add the output port latch that is just a conversion of the switch input latch that is already there left over from the input switches. Add another memory decoder 74LS688 and a 29F040 Flash ROM for a 512KB "ROM drive". It would contain essentially a custom 512KB floppy disk image and could boot just like a floppy. Actually I think a raw image of a 360K floppy would work "as is" or nearly so assuming the FDC BIOS code is able make it look like a drive to the PC's main BIOS.

                            The key is being able to reuse/modify the IO port decoder circuitry for the latch. The PC8477B/DP8473 has a "hole" in its registers at 0x6 where we can fit in a IO port within the existing range of the FDC. Otherwise it would require its own duplicate IO port decoding logic *or* use twice the IO addresses for a single device. Once we have the latch available adding in the memory decoder and the Flash ROM use only a couple more components plus some passives.

                            I think it is an efficient design to just have a reliable permanently resident small ROM for BIOS/config and a separate Flash ROM for the data. Trying to use one chip for both would be complex because you'd have to keep at least one page of the Flash in memory at all times while trying to switch another page. It is possible but would require some complex glue logic and more parts. It requires only a few parts to just use a small BIOS ROM and a larger Flash memory as separate subsystems *and* it decouples the BIOS ROM from the Flash ROM which allows it to be an optional component -- potentially saving costs.

                            Tonight I will update the schematic and post it for review. Since the changes are relatively modest it should take only a few days to update the PCB layout and optimize the trace routing for a prototype board.

                            Thanks and have a nice day!

                            Andrew Lynch

                            Comment


                              #89
                              Originally posted by lynchaj View Post
                              Tonight I will update the schematic and post it for review. Since the changes are relatively modest it should take only a few days to update the PCB layout and optimize the trace routing for a prototype board.
                              Hello Andrew,
                              I look forward to the new schematic, the idea is awesome, thank you.

                              Lucas

                              Comment


                                #90
                                Originally posted by lynchaj
                                ... frees up what used to be an input port for switches now can ...
                                Bugger, I love me some switches, mostly because I have a tendancy on some machines to move a lot of bits around and reconfigure things (e.g. my 'drive-testing' 386).

                                It's not important but a couple of questions:

                                - would it be possible to allow the configuration for drives 0 and 1 to be controlled by the computer's BIOS at all? And let the controller configure drives 2 and 3 (if fitted)?
                                - would there be a 'press KEY to configure' on startup?

                                Just trying to picture ways I could quickly configure drives without having to boot in to an OS first (but at the end of the day its a 'nice to have' rather than a 'must have')
                                Twitter / YouTube

                                Comment

                                Working...
                                X