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

HIMEMV2 or equivillent PROM

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

    #61
    Originally posted by Chuck(G) View Post
    Nah, it's not big--it'll fit easily into a small flat-rate Priority Mail box.
    Well, sounds like ibmapc is determined to send you big bucks, so I'll stand by in case his wife says no.

    Comment


      #62
      I will say that I was amazed at how slow stuff shipped first class from Canada takes to get across the border. I picked up a bunch of EEPROMs--good price, but they took three weeks to get here. In contrast, I typically get stuff from Hong Kong in about 5 days or less.

      I thought the US and Canada were part of NAFTA, so the hold-ups in shipping are really strange. Fast, cheap shipping is good for business, or hasn't Canada Post/Postes Canada figured that out yet?
      Reach me: vcfblackhole _at_ protonmail dot com.

      Comment


        #63
        Tell me about it.

        Somebody sent me some diskettes from N Dakota a while back; took 4 days and cost $4.00. I copied them and sent them on in the same box to a pal in Winnipeg (just across the border from N Dakota, so the same distance); cost me $10 and took 3 1/2 weeks.

        Comment


          #64
          Hey Chuck(G),
          Please check your PM's.

          Comment


            #65
            Not sure if I should put this here or start a new thread

            Hey Chuck,
            I've been stairing at the equations in U44V2M.EQN(That you created for programming the GAL to replace U44), trying to figure out what they mean. I've also been studying the document by Cy Atkinson, trying to reconcile the two, but I just can't get my head around it. One thing that confuses me is the equation:
            /Q2=/A3
            would that be the same as:
            Q2=A3
            From info on the net, I've learned that" /"=NOT, "*"=AND,"+"=OR, but I just haven't had that "A-HA" moment. Maybe you could shed some light on this to get me beyond my mental blockage.

            Code:
            EQUATIONS
            /Q2 =
                       /A3
            /Q1 =
                       A7*A3*A2*A1*/A0 +
                       /A3*/A2 + /A2*/A1 + /A7*/A2
            /Q0 =
                      /A7*A5*/A4*A3*A2*/A1 +
                      /A7*A5*A4*A3*A2*/A0 +
                      A4*A3*A2*/A1*/A0 +
                      A7*A5*A3*/A2*A1 +
                      A7*A3*A1*A0 +
                      A3*A2*A1*A0

            Comment


              #66
              The rules for EQN2JED are a little strange. If a pin (input or output) is declared as low-active in the pin assignment list, then if the pin is used as a negated term in the equations, it becomes high-active. Confusing? You bet.

              Fortunately, in the EQN file for U44, all pins are declared high-active, so Q2 is a straightforward assignment of A2. You could just as easily have said Q2 = A3, but since the GAL uses active-low outputs, it makes sense to keep them all that way. For that matter, any De Morgan equivalent assignment could be used on any of the pins, but since they're talked about as SOP terms, it makes sense to keep the equations looking like that.
              Reach me: vcfblackhole _at_ protonmail dot com.

              Comment


                #67
                Originally posted by ibmapc View Post
                One thing that confuses me is the equation:
                /Q2=/A3
                would that be the same as:
                Q2=A3
                Code:
                EQUATIONS
                /Q2 = /A3
                As Chuck says the answer is yes. The reason to have an equation where the output simply follows the input is to 'buffer' the input signal. The GAL output has good drive capability and can drive a lot of loads.
                Last edited by dave_m; January 17, 2012, 09:51 AM. Reason: typo

                Comment


                  #68
                  Originally posted by dave_m View Post
                  As Chuck says the answer is yes. The reason to have an equation where it output simply follows the input is to 'buffer' the input signal. The GAL output has good drive capability and can drive a lot of loads.
                  Well, actually, the idea here was to replace a bipolar PROM with a GAL with a minimum of fuss. In this case, all one has to do is extend the ground pin to handle the move from a 16-pin PROM to a 20-pin GAL. All of the other lines match up. I really like programmable logic!

                  Although it probably doesn't matter in this case, the other reason would be to match up propagation times of the signals. But it can matter in other cases.
                  Reach me: vcfblackhole _at_ protonmail dot com.

                  Comment


                    #69
                    So, if we look at the first part of the next equation:

                    /Q1 = A7*A3*A2*A1*/A0

                    If A7=1 and A3=1 and A2=1 and A1=1 and A0=0 then /Q1=1 so Q1=0 ?

                    Have I got that right?
                    Or am I all backwards?

                    Comment


                      #70
                      No, that's right.

                      If you're handy with C or even BASIC, you can take the equations and construct your own truth tables to verify the equation.
                      Reach me: vcfblackhole _at_ protonmail dot com.

                      Comment

                      Working...
                      X