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Thread: Using an LCD monitor on a IIGS

  1. #1

    Default Using an LCD monitor on a IIGS

    I know this has been discussed in the past, but I can't seem to find the threads (probably ignorance on my part). I have a board on my IIGS which allows me to connect the IIGS to an LCD monitor. The results are acceptable, but still not very good.

    On eBay, there is a seller who is selling a unit (here) advertised as for the IIGS in the ad title, but when you read through the ad text, the IIGS is not mentioned at all... nor is Apple itself. I contacted the seller & asked specifically if they have tested the device with an Apple IIGS and here is the response I received (the same ad appeared with two different titles):

    "These two listings function exactly the same. Important requirement to use this product is the source device must be outputting CGA signal at Horizontal 15.73, or, 15.62 KHz + Vertical 60, or, 50 Hz Non-interlace. The same requirement goes for Apple IIGS. Based on the feedback we received, some Apple IIGS user has met the frequency requirement, and some did not. Therefore, please find out about the signal frequency before purchasing."

    My question pertains to the last half of the response: Does it make sense that some Apple IIGS units would meet those output specs, and others wouldn't? Would 0.11 KHz difference matter, and what are the chances that there is this much variation in IIGS units?

    In refurbishing Apple IIs these past few years, I have seen what, to me, is an extraordinarily high variation within a model. Much of that variation appears to me to be the result of exactly where & when a component was manufactured. One small example: on some Apple IIc cases, the top and back panels are one single, molded piece, whereas in other IIc units, the back plate is a separate piece from the top of the case, held together with several snap-hooks. In another thread here, someone else pointed out several differences in IIe motherboards. Of course, you would expect some differences to crop up over time, much as you would in minor variations in software (eg., v 3.01 vs 3.02). But would there be such variation within an Apple IIGS that such a peripheral as above might work on some IIGS units and not others?


    P.S. If ignorance is truly bliss, why am I not supremely happy???

  2. #2


    Its doubtful any machine puts out a perfectly stable 15.75khz scanline, thus any piece of equipment is going to have some headroom built into the design. That being said, the Cypress device being advertised has had mixed reviews with how well it works.... or doesn't work. It really is that random. Cypress products look good on paper, but the quality control issues prevent me from actually recommending them.

    The GBS-8220 is another cheap upscaler that works for some, but completely fails for others. Its one device that you get what you pay for. Everyone complains about the cheapo units not working right 100% of the time, or lack support of a video mode (like PAL, but this is more of a problem with the Amiga), yet the same problems don't exist on the high end units (ex: Micomsoft XRGB series). This guy has a nice review of various upscalers. For comparison, the Apple IIgs outputs what he refers to "240p" video.

  3. #3


    Is there a reason why something like an old Infocus adapter wouldn't work? I have one at work, funnily enough, we still use it for our daily announcements for the students. Mac mini -> HDFury -> VGA -> InFocus -> closed circuit TV. Looks fine to me, and you can make all sorts of manual adjustments like contrast, gain, position (H + V), etc. I think we bought it second hand for $40 at some point.

    Edit: HERP DERP! Wrong direction. You're going from IIgs to LCD. :P Nevermind.

  4. #4


    Quote Originally Posted by Drken View Post
    "These two listings function exactly the same. Important requirement to use this product is the source device must be outputting CGA signal at Horizontal 15.73, or, 15.62 KHz + Vertical 60, or, 50 Hz Non-interlace.
    NTSC color video (the American TV standard) uses a horizontal frequency of 15.734 kHz and a vertical refresh rate of 59.94 Hz.
    These were both slightly modified from the original specs used by black & white TV due to the limitations of vacuum tube-based equipment that was in use when color TV was introduced in the 1950s. Black & white TV was originally 15.75 kHz horizontal and exactly 60 Hz vertical. This slight change in frequencies did not affect older B&W TVs because it was still well within normal tolerance.

    Therefore whether the IIGS puts out 15.734 kHz video at 59.94 Hz or 15.75 kHz video at 60 Hz, it should not matter to the upscaler. I've seen other manufacturers claim a +/-5% tolerance on the input frequencies, and this is well within that range.
    Last edited by vwestlife; December 14th, 2012 at 12:34 PM.

  5. #5
    Join Date
    Mar 2010
    Florida, USA


    I have one of the linked Ambery scalers. I haven't built an adapter for it for my IIgs. I guess I'll toss it on the to-do list... though it'll be awhile out before I can get to it. I can tell you that the Atari ST crowd at Best Electronics has recommended these devices for use with the Atari ST for years. (my apologies for those of you who click the link - Bruce and his wife are great people to deal with, but he's back in 1995 in regards to his web development habits!!)
    Currently seeking:
    * Roland MPU-401/AT (with daughter card header)
    * Magitronic K-156 Keyboard (5pin DIN w/ XT-AT switch)
    I also collect PC and C64 Sierra On-Line software!

  6. #6


    The GBS-8220 is the unit I currently run on my IIGS. Not sure if the Ambery unit would be a significant improvement or not. I followed all the links given here, and to be honest, became more confused than ever by the time I was finished! Again, my ignorance shines through.... quite brightly, I might add!

    What is the relationship between Atari and IIGS video output? And has anyone done a direct comparison of the GBS-8220 & Ambery units? (I apologize up-front if I missed it in the links I followed.) From the original email I received from the Ambery unit vendor on eBay who I contacted, he made it sound like the variation of results - the Apple IIGS will or will not work with it - was the result of production variabilty within Apple, but from what I gather from the comments here, it is more an issue with the quality consistency of the Ambery products. Is that a fair assessment?

  7. #7


    The video output between the two should be exactly the same, basically progressive RGB with TV scanrates. The exception being the ST's 640x400 monochrome mode, which is VGA like. The Ambery unit seems to have a problem with properly handling 240p according to this thread: . It interprets the video as 480i and tries to deinterlace it, causing artifacts. Its a common problem with upscalers, so folks tend to seek out the units that DO work properly.

    There are a ton of SCART-RGB to HDMI scalers out there now in the area of $50 that would be a better buy with modern LCD monitors, many of which can properly handle 240p video. (see Fudoh's review page above) The adapter often recommended by IIgs users, but now discontinued was the Highway 100 RGB adapter. I have no experience with it, so I can't say how well it worked or how good the image quality was.

  8. #8


    I am sublimely ignorant of such details as Horizontal KHz and interlace vs. non-interlace, but my IIGS uses this $33 converter board to produce this VGA output on an LCD monitor:


    I like to tinker, and after considerable trial and error I discovered that the converter worked when the IIGS 15-pin RGB output is connected to the board like this:

    Pin #1 to black GND wire
    Pin #2 to red R wire
    Pin #3 to gray S wire
    Pin #5 to green G wire
    Pin #9 to blue B wire

    As I said on Drken's website, where he first alerted me to this converter, "There's some distortion from the converter output, such as wavy lines on the system 6.01 desktop background and occasional hiccups that bounce the screen image a bit. But it's not too distracting."

    Correct me if I'm wrong, Dr. Ken, but I think this is the setup you describe as "acceptable, but still not very good." I agree, and I'm looking forward to something better from the contributors to this thread. But in the meantime, I just wanted to share the details of a $33 converter that actually produces an acceptable display on a VGA monitor.

  9. #9


    Part of the output problem is the up-scan converter, the other part is the scaler in the LCD. Most of the cheap adapters were never intended to be used with LCDs to begin with. Jim Maricondo ran into the same problems with the XRGB2 on LCD displays (see: ). Based on personal experience, I can say the XRGB2plus in conjunction with a CRT works great, not so much on a LCD. From what I read, the problem has something to do with "dot clocks". The XRGB2 offers an adjustable dot clock that can be tweaked to improve display quality, something the cheapo adapters lack.

    The other problem is the LCD's video scaler distorts the video when stretching it to the native resolution of the panel. The best up-scaler will be one that converts the IIgs video to the LCD panel's native resolution and preferably using digital interconnect to eliminate a round of digital-analog-digital conversion.

  10. #10


    I use an Extron 118 plus, it does EXCELLENT on a CRT display and decent on a LCD, but you do get some artifacts from scaling of LCD since its analog, but I would venture to say it looks a bit better than gib's pic, but still not perfect.

    I think the only "perfect" solution for VGA out of a IIgs would be a VGA card, like the "second sight" or possibly the cart blanche card, and I don't know that either are real obtainable, and I would still question their output on an LCD with its scaling (unless you were running 1024x768 mode on a second sight on a 1024x768 LCD panel, that would probably be crisp).
    My Vintage computer/blog site
    Searching for a keyboard for a WYSEpc WY-1100.


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