Announcement

Collapse

Forum 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.


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.


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.



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.


"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.

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

WTB: 286 to 386 / 486 Accelerator

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

    WTB: 286 to 386 / 486 Accelerator

    Been looking for a year now. Basically looking to upgrade my Teradrive PC from a slow low end 286 to a more powerful 386 or 486. Any help would be most appreciative!! Thanks!


    #2
    Such an upgrade isn't really practical. I would at most aim for a 386SX because anything faster is a waste. A 386SX is similar enough to a 286 that upgrades that use it aren't terribly complex and it would likely be more compatible than a huge interposer full of GAL and PAL chips. The 386 SX isn't much faster, but it would at least give you 32 bit protected mode and allow you to run 32 bit applications.

    Any 386/486 upgrade is going to be severely crippled due to the 286 bus. You're effectively hobbling full 32 bit CPUs (in the case of the 386DX and 486) onto a 16 bit data bus and 24 bit address bus. To make a bad situation even worse, the 286 has a multiplexed address and data bus, further slowing down an already slow system. And if that wasn't already bad enough, nothing on the motherboard side is going to run faster, so you're going to be stuck with the same 10 MHz 16 bit multiplexed system bus. Any time the CPU has to do out to the motherboard, it's going to be crippled and spend lots of time waiting for the system to give it something to do.

    The Teradrive is also very RAM limited due to the upper address lines of the memory slots not being connected. The maximum amount of RAM it can handle is 4 MB. There is a mythical hack I've read about to connect the upper address lines and get more memory, but that's a big headache to do.

    Comment


      #3
      Such an upgrade isn't really practical.
      I don't see why that matters, especially since there is no other way to speed-up that system. Also, many of these upgrades include L1 cache and double the CPU clock, so as for raw processing power, you can get quite a boost.

      I have a Schneider Tower AT and been looking for such an upgrade as well.

      Comment


        #4
        Originally posted by GiGaBiTe View Post
        Such an upgrade isn't really practical. I would at most aim for a 386SX because anything faster is a waste. A 386SX is similar enough to a 286 that upgrades that use it aren't terribly complex and it would likely be more compatible than a huge interposer full of GAL and PAL chips. The 386 SX isn't much faster, but it would at least give you 32 bit protected mode and allow you to run 32 bit applications.

        Any 386/486 upgrade is going to be severely crippled due to the 286 bus. You're effectively hobbling full 32 bit CPUs (in the case of the 386DX and 486) onto a 16 bit data bus and 24 bit address bus. To make a bad situation even worse, the 286 has a multiplexed address and data bus, further slowing down an already slow system. And if that wasn't already bad enough, nothing on the motherboard side is going to run faster, so you're going to be stuck with the same 10 MHz 16 bit multiplexed system bus. Any time the CPU has to do out to the motherboard, it's going to be crippled and spend lots of time waiting for the system to give it something to do.

        The Teradrive is also very RAM limited due to the upper address lines of the memory slots not being connected. The maximum amount of RAM it can handle is 4 MB. There is a mythical hack I've read about to connect the upper address lines and get more memory, but that's a big headache to do.

        Oh I've already connected the lines needed for the RAM, but apparently it's limited in the bios as well, so I'm having a friend go over that

        https://www.ebay.com/itm/333999239793 I made these for the teradrive as well seeing how that's another one of its short comings, but yeah...the CPU is a problem currently. I do have multiple 286--->486 accelerators, but the problem is they are rather long and don't fit in the teradrive in that particular orientation.

        Comment


          #5
          These are the ones I currently have (minus the top one as that's a 386 to 486BL3. Problem is they are all orientated where they slam into the riser card >.<
          You do not have permission to view this gallery.
          This gallery has 1 photos.

          Comment


            #6
            Well if you could find the weird "male" PLCC connector, you could theoretically make an interposer to move/rotate the position of the upgrade board. Though I think you'd then run into a problem with height due to the bracket above and the ISA backplane.

            Comment


              #7
              Originally posted by GiGaBiTe View Post
              Well if you could find the weird "male" PLCC connector, you could theoretically make an interposer to move/rotate the position of the upgrade board. Though I think you'd then run into a problem with height due to the bracket above and the ISA backplane.
              Believe me, I've tried that. Even with proper support chips on the position board it didn't work.

              Comment


                #8
                Maybe something like that:
                http://www.cpushack.com/2014/08/30/i...6-286-upgrade/

                Comment


                  #9
                  Yeah, that would be great, but I can't find one heh.

                  Comment


                    #10
                    Originally posted by coolmod121 View Post

                    Believe me, I've tried that. Even with proper support chips on the position board it didn't work.
                    Did you make a PCB interposer, or did you run bodge wires on like a piece of perfboard? I remember seeing another attempt at a 386 interposer, where the guy just used a bunch of bodge wires and it was super unreliable because it caused signal integrity issues. I'd think you'd have to make it a straight up interposer, rather than kicking it off to one side because that'd introduce trace length and noise.

                    With the relatively low number of pins, you should be able to do it in a 3-4 layer PCB. More complicated interposers, like the Evergreen 586 seem to only have 4 layers.

                    Comment


                      #11
                      I did actually make a PCB interposer with the help of a friend. It was a no go, according to him the original PCB was already very noisy and introducing more with relocating it wasn't reliable.

                      Comment


                        #12
                        That's interesting. Well you could always do like the guys over at 68kmla and roll your own upgrade board by reverse engineering. It'd give you an opportunity to clean the design up, quite a bit of work though.

                        Comment

                        Working...
                        X