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

Blistering Speed upgrade for a model 4 CPU

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

    Blistering Speed upgrade for a model 4 CPU

    so tonight I opened one of the two "speedup kits" that I have acquired in a mix match box of parts.
    this kit is simple, a board that will end up plugs into the Model 4 U3 and the U3 chip onto the board, and swapping out the Z80A (4mhz) for a Z80B (6mhz) CPU. simple… well, in reality, take a lot longer to take apart the computer internal to get to the mainboard than apply this kit. simple it IS!
    NB: I have 150ns 4164 chips in the system already installed and strongly suggested to get good speeds 120ns would be better.
    step one: I found a program called "clkspeed/cmd" for model 4 (runs on TRSDOS/LSDOS 6.x) and ran a benchmark to get an idea, 3 mins later the result was on the screen, 3.62Mhz at top speed.! with the Z80A stock from TRS.

    jkcMgsg.png

    turned off the machine, found the U3 chip, removed it carefully (notice some mod already one it) and put it on the alpha speedup board and reinserted the board in the place where the U3 was pulled from

    EdxjoJ0.png

    Next, I replaced the z80a with the z80b that was provided in the kit

    U3zqY1A.png

    closed her up and ran again the same test and low and behold “speed”… Seriously, now calculations at 2 Mhz took 103 seconds, 57 seconds in 3.66 Mhz now barely take 45 seconds in 4.64Mhz ! the kit claim to fame only 5.x Mhz speeds, so I am close and better speed would be acquired with faster ram I am sure but happy anyway.
    Maybe I should put a heatsink or a water cooling system. Kidding aside, 1Mhz was a lot in 1982, and at 65$ this kit WAS the easier and cheapest kit available on the market at the time.

    gUFK0gi.png
    TRS-80 MODEL 4, 128K RAM, 360K & 720K, Gotek FDD, FreHD SDCARD HDD, GURU RS232-WIFI MODEM, DWP210
    Eeprom Prog: Inspiron 660s, I5-3330s, with BK-844USB
    Gotek Prog: Dell D520, Dual-Core Intel, 8GB, 500GB HDD, 15" LCD
    Web Site: https://texastandyrestoration.org/

    #2
    Nice, board looks very simple. Ripe for remanufacturing ?
    Current fleet
    TRS80 Model 4 - BBC B - Tatung Einstein - PCW9512 - PET 3032 - C64 - ZX81 - Spectrum 48K - Amiga A500 - Apple II europlus - Apple iMAC G3. Sharp MZ-80K. - IBM 5160 XT - Multibus 286/10 - Micro PDP 11/73 - Rainbow PC100A - MicroVax II - MicroVAX 3100, 3300, VAX 4000 VLC & 4000 Model 96 - AlphaStation 225 Apricot PC - Apple Performa 6200 - Apple Mac IIcx - Osborne 1 - ACT Sirius 1

    Comment


      #3
      Originally posted by Gary C View Post
      Nice, board looks very simple. Ripe for remanufacturing ?
      yeah, I guess I still have another I was considering it, it's a really simple board, but is there really a demand for it. working on taking wait times out to get more out of it and test 120ns ram to see if that makes any differences as well.,
      TRS-80 MODEL 4, 128K RAM, 360K & 720K, Gotek FDD, FreHD SDCARD HDD, GURU RS232-WIFI MODEM, DWP210
      Eeprom Prog: Inspiron 660s, I5-3330s, with BK-844USB
      Gotek Prog: Dell D520, Dual-Core Intel, 8GB, 500GB HDD, 15" LCD
      Web Site: https://texastandyrestoration.org/

      Comment


        #4
        I tracked the article that mentions for Model 4 NGA (not for 4GA models) motherboard that lifting the Pin 27 of the CPU would remove the wait states of the CPU (article can be see at https://archive.org/details/computer...p?q=z80+pin+27) so here we go , pulled the new Z80B chip and bent gently the 27th pin and then re-instated it back unto the board, after reassembly. ran clkspeed again so now from the base 3.66 to 5.17 Mhz ( +41.25% cpu speed increase) with a little kit and a bent pin.. still running 150ns chips as ram.

        DK7XfEN.png
        TRS-80 MODEL 4, 128K RAM, 360K & 720K, Gotek FDD, FreHD SDCARD HDD, GURU RS232-WIFI MODEM, DWP210
        Eeprom Prog: Inspiron 660s, I5-3330s, with BK-844USB
        Gotek Prog: Dell D520, Dual-Core Intel, 8GB, 500GB HDD, 15" LCD
        Web Site: https://texastandyrestoration.org/

        Comment


          #5
          If we can get good images of the board and work out where the connections go under the chips, I would have a go.
          Current fleet
          TRS80 Model 4 - BBC B - Tatung Einstein - PCW9512 - PET 3032 - C64 - ZX81 - Spectrum 48K - Amiga A500 - Apple II europlus - Apple iMAC G3. Sharp MZ-80K. - IBM 5160 XT - Multibus 286/10 - Micro PDP 11/73 - Rainbow PC100A - MicroVax II - MicroVAX 3100, 3300, VAX 4000 VLC & 4000 Model 96 - AlphaStation 225 Apricot PC - Apple Performa 6200 - Apple Mac IIcx - Osborne 1 - ACT Sirius 1

          Comment


            #6
            Originally posted by Patrick Bureau View Post
            I tracked the article that mentions for Model 4 NGA (not for 4GA models) motherboard that lifting the Pin 27 of the CPU would remove the wait states of the CPU (article can be see at https://archive.org/details/computer...p?q=z80+pin+27) so here we go , pulled the new Z80B chip and bent gently the 27th pin and then re-instated it back unto the board, after reassembly. ran clkspeed again so now from the base 3.66 to 5.17 Mhz ( +41.25% cpu speed increase) with a little kit and a bent pin.. still running 150ns chips as ram.
            Is removing the wait states reliable? I mean, isn't the whole point of wait states because they're necessary? Or are the chips you're using fast enough to not need them?


            Comment


              #7
              Of course TRS80 has no way to know what speed RAM chips is installed so data is either available or it's not on a read.

              Many of these issues are discussed in Misosys quarterly regarding XLR8.

              Once you get so fast most motherboard will start getting flakey. I forget that speed but I think it's in quarterly's.

              Keyboard drivers and others start failing. Delay loops running too fast.

              Comment


                #8
                Originally posted by whartung View Post

                Is removing the wait states reliable? I mean, isn't the whole point of wait states because they're necessary? Or are the chips you're using fast enough to not need them?

                The wait states were added by Tandy for the early Model 4's. AFAIK, none of the model 4Ps or later Model 4s had the wait states.

                Comment


                  #9
                  What I mean to say is speed of memory is not going make it run faster or slower.

                  It's more accurate to say it partially dictates speed CPU can run with or without errors.

                  Speed of I/o ports is another part limiting CPU speed.

                  With trs80 doing much I/o counting on delay loops to run at a specific speed or counting time to repeat keyboard keys held down etc.

                  It's part of reason I cannot run my emulator at full speed without all sorts problems.

                  Comment


                    #10
                    Using xlr8 upgrade as an example.

                    I think most all motherboard requires wait states.

                    Z180 has built in wait state generator that can be changed under program control.

                    Stock TRS80 does not have this.

                    Comment


                      #11
                      On the first issue of speeding up the system;
                      The FDC will be fine and trouble-free up to 6MHZ, at 8Mhz (z80H) there is a change that needs to be done (Seatronic's speedup board explains it) to permit no issues with the floppies.
                      The RS232 at 6-8Mhz is fine as it uses another control signal regimented at 5mhz anyways.
                      The wait state was only on the Older NGA boards (model 3/4) once the Gate array boards came out for the Model 4,4d,4p there were no more *wait* being used. and the reason why the pin 27 mod is only applicable to the NGA board, doing this on a GA board will just make the machine stop working entirely), but at 5MHZ there are no changes to be done elsewhere except 150ns 4164 DRAM
                      As for the RAM Speed not being a factor that also isn't accurate, 200ns, 150ns, 120ns, or 100ns speed of the ram, does matter if you are pushing 5Mhz and running 200ns you will encounter issues of course(lockups mostly), and that is why all speedup kits recommend 150ns up to 6mhz and 120-100 for the 8mhz kits.
                      Last edited by Patrick Bureau; October 27, 2021, 08:58 PM.
                      TRS-80 MODEL 4, 128K RAM, 360K & 720K, Gotek FDD, FreHD SDCARD HDD, GURU RS232-WIFI MODEM, DWP210
                      Eeprom Prog: Inspiron 660s, I5-3330s, with BK-844USB
                      Gotek Prog: Dell D520, Dual-Core Intel, 8GB, 500GB HDD, 15" LCD
                      Web Site: https://texastandyrestoration.org/

                      Comment


                        #12
                        Yea sorry. Speed of RAM don't control speed of trs80.

                        Either RAM contents are available on a read cycle or they are not. I have RAM that would work at a higher clock speed than rated and also had opposite.

                        This comment is related to trs80 had no memory controller. It has no way of knowing if RAM is present or not. other than getting garbage back on a read. In some systems with memory controller it knows if RAM present and it's speed. They are so tightly coupled that the controller knows if not present.

                        Sadly we had none of this.

                        Having speed up a couple hundred model 4 ( I never worked on anything but 4) I can tell you some machines motherboard will flake out long before 6mhz.

                        Not RAM but other issues. Keyboard interface was one of 1st to fail.

                        If you look at source for floppy driver you will see delay loops saying things like LET IT SETTLE A BIT ETC.

                        Some motherboard will be tolerate of speed increase where as I had others that just never did.

                        Back in day there was a big stink at RS about wait states. Marketing between companies of the day were attacking each other on wait states in each others machine claiming public was mislead.

                        I had people wanting me install 100ns memory thinking machine would run faster. Of course trs80 has no idea speed of memory outside CPU as long as it worked.

                        I/O failures were avoided by using loops mainly DJNZ instruction, to slow down external read/writes. Changing speed of CPU of course changes amount of delay in these loops.

                        SVC @pause suffers as now you pause about 80 percentage less.

                        There were a lot of patches to fix some of these published in Misosys quarterly.

                        Keyboard is most sensitive. Heck they had a lot of problems making software scanned keyboard work reliable at 4mhz.

                        Only way I would be sure if trs80 had wait states happening would be to put a scope on wait pin of CPU and watch it. I was always under impression it had a least one but never really tested it.



                        Comment


                          #13
                          that's interesting though not surprising that some motherboards were incapable to tolerate speed upgrades or even baseline 4mhz function, I have often observed M4 board (and as well in m3s) motherboard of "a" revision having been upgraded multipole time or repaired with bog-wires all over it, Often I found those motherboards to really need to be retired.
                          TRS-80 MODEL 4, 128K RAM, 360K & 720K, Gotek FDD, FreHD SDCARD HDD, GURU RS232-WIFI MODEM, DWP210
                          Eeprom Prog: Inspiron 660s, I5-3330s, with BK-844USB
                          Gotek Prog: Dell D520, Dual-Core Intel, 8GB, 500GB HDD, 15" LCD
                          Web Site: https://texastandyrestoration.org/

                          Comment

                          Working...
                          X