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

Another discussion of CGA/EGA on (relatively) modern monitors.

  • Filter
  • Time
  • Show
Clear All
new posts

    Another discussion of CGA/EGA on (relatively) modern monitors.

    I know this horse has been beat to death, but I stumbled across this video by 'Artifact Electronics' the other day where in the process of examining the old PC clone in question, the individual goes about connecting a CGA (though I actually believed that to be an EGA card when he shows it at the end, and where he mentions the 21Khz) to an ordinary Samsung Multisync LCD monitor, made long after CGA/EGA ceased to be relevant. I know the real old Multisyncs did this, obviously, as that's why they were called that, but I was shocked to see a modern one do it in the video.

    Has anyone else experimented with trying this on other CRT or LCD monitors, using the analog or DVI connectors and maybe some resistors?

    Some LCD monitors can get that low--I've got a couple ASUS wide-screen ones that succeeded in syncing to the output of an AT&T 6300, which, I believe is in the same range.

    this may be of interest
    Reach me: vcfblackhole _at_ protonmail dot com.


      Thanks for the link, Chuck.

      Everyone else, just to be clear, I am aware of the projects dedicated to this process, but this thread is about monitors that do it naturally. Also, I meant NEC Multisync. Samsung had Syncmaster.


        Hi Folks, A CGA/MGA converter that works!

        I've been using mine for a month.



          Originally posted by jjandersoj View Post
          Hi Folks, A CGA/MGA converter that works!

          I've been using mine for a month.

          Yep, that's a modified version of Retro Canada's (Luis Antoniosi's) MCE2VGA converter. I built and sold a bunch of those last year and continue to use one myself. It works VERY WELL INDEED!


            Actually, support for 15 kHz video isn't a big surprise.
            Modern monitors share a lot of circuitry with TV sets, and TV sets are supposed to support PAL and/or NTSC - and both are 15 kHz.
            Some monitors have lower frequencies artificially disabled, but many don't, so it just works.
            However, it's somewhat surprising to see that monitor support 21 kHz, as that's neither TV nor VGA, it's specific to EGA and nothing else.
            And yes, that video card is a typical EGA clone, with 256 KB of DRAM.
            Last edited by Xacalite; March 25, 2019, 10:43 PM.


              Support for rates that low is actually quite common amongst modern LCD TV's -- even the giant 60"+ ones -- for one simple reason. It makes it easier to support old 480i broadcasts which uses the same pulse times as 240p. Same reason you can just make *nix modelines for 854x540p -- an unofficial / nonexistant mode -- and it works just fine.

              In general so long as you get the VSYNC pulses 150 microseconds wide and your HSYCN at 8ms with a sufficient front and back porches it tends to work on modern displays.

              Something I've been finding out by playing around is that the whole concept of "pixel clocks" is mostly BS used to make the math simple. So long as you have the sync pulses and porches the right width, and the correct number of scanlines for an existing mode output, you can make nearly any visible width you want on most any display. If you have full control over the "pixel clock" whilst outputting the horizontal data, you can even send 1920 wide to a CGA display... though the physical low ppi of the display makes it look as bad as 640 does on a color TV.

              I was a little surprised to find that out... that the whole pixel clock thing is more fantasy than fact. Case in point right now I'm playing around using a Teensy 3.0 with a pair of SPI SRAM and a old Sierra RAMDAC to output 960x480 on a normal VGA analog and it works just fine on every display I'm throwing at it from an old mono IBM CRT really not designed to go past 640x480, to a 20" IBM CRT, to an older Dell 20" LCD, to my relatively new 42" media center LCD.

              (the whole SPI SRAM thing is awesome, just switch them to QPI output and dump four bits each from two chips directly into the RAMDAC, all you need to do is make sure the driving clocks are right.)

              Bottom line, if the sync pulses are within the displays rated range and of sufficient width, it tends to work... and modern displays -- pretty much all of them -- accept an absurdly wide range of horiz and vertical rates. LCD TV's often more so than CRT's thanks to the use of scan converters.

              Just beware they usually take a full second worth of sampling frames to figure out what you're doing before they allow display after changing sync rates, and even the slightest hiccup in sync can cause them to go back into sampling with a blank display.
              Last edited by deathshadow; March 26, 2019, 07:17 AM.
              From time to time the accessibility of a website must be refreshed with the blood of owners and designers. It is its natural manure.


                I think the earliest example of this was a fellow who figured out how to get a VGA image (monochrome) using nothing more than an ATMega8 MCU. Of course, it doesn't have enough memory for graphics, so text only.
                Reach me: vcfblackhole _at_ protonmail dot com.


                  Originally posted by Chuck(G) View Post
                  I think the earliest example of this was a fellow who figured out how to get a VGA image (monochrome) using nothing more than an ATMega8 MCU. Of course, it doesn't have enough memory for graphics, so text only.
                  Yup, and nowadays people are pushing 120x60 4 color graphics out of a ATMega328p. I could almost use that cheap little bugger as my CRTC, if not for the need of a specific timing in a 19.2khz pixel clock just to get me to 480 width... with 5 clocks allowing me to control that timing on two lines 96mhz is my minimum.

                  I could try playing with clock delays, but honestly something like a bottom end Maxim ARM4 at 96mhz costs the same as the 328p these days should I reach the point of making these for other people. (and right now I have a teensy 3.0 sitting there gathering dust)
                  From time to time the accessibility of a website must be refreshed with the blood of owners and designers. It is its natural manure.


                    Yeah, ARM is so cheap that I don't even consider earlier families like MIPS or ATMega or PIC anymore.

                    One of these days, it might be fun to play with some of those 3 cent MCUs. Heck the solder would probably cost more.
                    Reach me: vcfblackhole _at_ protonmail dot com.