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Discussion in 'Electrical Engineering' started by [email protected], Jun 20, 2008.

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  1. Guest

    What aspects of a DVI switch (KVM for example) would affect its ability to
    handle higher video modes such as 1920 x 1200 (when it can handle 1600 x 1200)?
    I'm curious why there are so many DVI switches that have a 1600 x 1200 limit
    and can't do 1920 x 1200.
     
  2. krw

    krw Guest

    What refresh rate? Perhaps it needs Dual Link DVI (DVI-DL) to get
    the refresh rate you're looking for at 1920x1200.
     
  3. Guest

    | In article <>,
    | says...
    |> What aspects of a DVI switch (KVM for example) would affect its ability to
    |> handle higher video modes such as 1920 x 1200 (when it can handle 1600 x 1200)?
    |> I'm curious why there are so many DVI switches that have a 1600 x 1200 limit
    |> and can't do 1920 x 1200.
    |
    | What refresh rate? Perhaps it needs Dual Link DVI (DVI-DL) to get
    | the refresh rate you're looking for at 1920x1200.

    1920x1200 (WUXGA) is a single link format. Single link can go all the way up
    to 2098x1311 for odd formats. 2048x1152 (non-standard, but sensible) format
    would also be doable on single link. Dual link could go up to 2960x1850.
     
  4. Guest

    | In article <>,
    | says...
    |> What aspects of a DVI switch (KVM for example) would affect its ability to
    |> handle higher video modes such as 1920 x 1200 (when it can handle 1600 x 1200)?
    |> I'm curious why there are so many DVI switches that have a 1600 x 1200 limit
    |> and can't do 1920 x 1200.
    |
    | What refresh rate? Perhaps it needs Dual Link DVI (DVI-DL) to get
    | the refresh rate you're looking for at 1920x1200.

    I suspect what the switch might be trying to do is mess with the EDID data.
    And its firmware isn't coded for more than 1600x1200. I just don't know if
    this was because the engineer coding it didn't know of 1920x1200 (unlikely)
    or if management interfered (more likely). Maybe it could be a documentation
    issue and it really would work with 1920x1200.
     
  5. Bob Myers

    Bob Myers Guest

    \
    Well, at least per the pixel clock limits on both single- and dual-link
    DVI, they sure could. The problem is, though, that the DVI standard
    never included a decent compliance certification test, nor is there any
    good spec on cabling, switches, and the like that would truly ensure
    that you can run full rates over any given comibination of such things.
    So as you approach the top-end clock spec, some will work, and
    some may not.

    Bob M.
     
  6. Guest

    |
    | | \
    |>
    |> 1920x1200 (WUXGA) is a single link format. Single link can go all the way
    |> up
    |> to 2098x1311 for odd formats. 2048x1152 (non-standard, but sensible)
    |> format
    |> would also be doable on single link. Dual link could go up to 2960x1850.
    |
    | Well, at least per the pixel clock limits on both single- and dual-link
    | DVI, they sure could. The problem is, though, that the DVI standard
    | never included a decent compliance certification test, nor is there any
    | good spec on cabling, switches, and the like that would truly ensure
    | that you can run full rates over any given comibination of such things.
    | So as you approach the top-end clock spec, some will work, and
    | some may not.

    I called one of the makers of one of the switches I found like this (Blackbox)
    and the guy I talked to tried to convince me that no one uses 1920x1200. My
    response was "but they do use 1600x1200 when monitors of that type are rare
    adn hard to find and are about to go out of production because the world is
    shifting to widescreen so they have enough space to display 1920x1080 video?".
    He didn't have an answer to that loaded question. I suggested he have the
    product sent back to engineering.
     
  7. Guest

    | | \
    |>
    |> 1920x1200 (WUXGA) is a single link format. Single link can go all the way
    |> up
    |> to 2098x1311 for odd formats. 2048x1152 (non-standard, but sensible)
    |> format
    |> would also be doable on single link. Dual link could go up to 2960x1850.
    |
    | Well, at least per the pixel clock limits on both single- and dual-link
    | DVI, they sure could. The problem is, though, that the DVI standard
    | never included a decent compliance certification test, nor is there any
    | good spec on cabling, switches, and the like that would truly ensure
    | that you can run full rates over any given comibination of such things.
    | So as you approach the top-end clock spec, some will work, and
    | some may not.

    Here's another one I found. It has a _higher_ resolution limit (1920x1440)
    but it has some suspicious words in the tech specs saying "This products is
    not intended for use with Widescreen displays".

    http://www.startech.com/item-specs/SV421DVI-4-Port-StarView-DVI-KVM-Switch.aspx

    So what could that possibly mean? Could it really be that these switches are
    messing around with the EDID data or other parameters affected by the specific
    geometry, and are not designed for the 16:10 geometries?
     
  8. Guest

    | In article <>,
    | says...
    |> What aspects of a DVI switch (KVM for example) would affect its ability to
    |> handle higher video modes such as 1920 x 1200 (when it can handle 1600 x 1200)?
    |> I'm curious why there are so many DVI switches that have a 1600 x 1200 limit
    |> and can't do 1920 x 1200.
    |
    | What refresh rate? Perhaps it needs Dual Link DVI (DVI-DL) to get
    | the refresh rate you're looking for at 1920x1200.

    How about this one?

    http://www.startech.com/item-specs/SV421DVI-4-Port-StarView-DVI-KVM-Switch.aspx

    It has a max resolution of 1920x1440. But it also says it is not intended for
    widescreen displays.
     
  9. To get my Samsung 20" 1280 * 960 I had to place a special order;although my
    graphic card (Asus ATI 2600 pro) is dual head, also comes with 2 DVI plugs,
    the monitor that the vendor matched, was a VGA one, so I had to use DAC->ADC
    with all cons. (www.cccira.gr) The order took 10 days to process, as if I
    was asking something exotic. Anyway, it's a good monitor.(It's widescreen).
    It cost 250 euros.
     
  10. Guest

    |
    | ? <> ?????? ??? ??????
    | |> In alt.engineering.electrical Bob Myers <>
    |> wrote:
    |>
    |> | |> | \
    |> |>
    |> |> 1920x1200 (WUXGA) is a single link format. Single link can go all the
    |> way
    |> |> up
    |> |> to 2098x1311 for odd formats. 2048x1152 (non-standard, but sensible)
    |> |> format
    |> |> would also be doable on single link. Dual link could go up to
    |> 2960x1850.
    |> |
    |> | Well, at least per the pixel clock limits on both single- and dual-link
    |> | DVI, they sure could. The problem is, though, that the DVI standard
    |> | never included a decent compliance certification test, nor is there any
    |> | good spec on cabling, switches, and the like that would truly ensure
    |> | that you can run full rates over any given comibination of such things.
    |> | So as you approach the top-end clock spec, some will work, and
    |> | some may not.
    |>
    |> Here's another one I found. It has a _higher_ resolution limit
    |> (1920x1440)
    |> but it has some suspicious words in the tech specs saying "This products
    |> is
    |> not intended for use with Widescreen displays".
    |>
    |> http://www.startech.com/item-specs/SV421DVI-4-Port-StarView-DVI-KVM-Switch.aspx
    |>
    |> So what could that possibly mean? Could it really be that these switches
    |> are
    |> messing around with the EDID data or other parameters affected by the
    |> specific
    |> geometry, and are not designed for the 16:10 geometries?
    |>
    |> --
    | To get my Samsung 20" 1280 * 960 I had to place a special order;although my
    | graphic card (Asus ATI 2600 pro) is dual head, also comes with 2 DVI plugs,
    | the monitor that the vendor matched, was a VGA one, so I had to use DAC->ADC
    | with all cons. (www.cccira.gr) The order took 10 days to process, as if I
    | was asking something exotic. Anyway, it's a good monitor.(It's widescreen).
    | It cost 250 euros.

    What I'm trying to do is switch from among 4 computers, 2 with HD15 analog
    video out, and 2 with DVI-D out. I want to run the DVI ones at 1920x1200.
    The analog ones would be at some lower 16:10 resolution, and be scaled up.
    The quality is not critical for the analog ones, but they need to at least
    maintain functionality without major distortion. Output from the KVM switch
    would go to a DVI-I to DVI-D + HD15 splitter, and both of those go into the
    same monitor. That way when the switch selects a DVI machine, digital video
    goes to the monitor, otherwise the monitor just gets analog.

    It needs to also have PS/2 keyboard/mouse without any use of USB conversion.
     
  11. krw

    krw Guest

    At 60Hz, yes. By 85Hz single link is out of gas. That was my point
    ("what refresh rate?"). Do follow along.
     
  12. krw

    krw Guest

    This monitor is 1920x1200. It is quite common for 24" LCD monitors.
     
  13. Guest

    | In article <>, phil-news-
    | says...
    |> |
    |> | |> | \
    |> |>
    |> |> 1920x1200 (WUXGA) is a single link format. Single link can go all the way
    |> |> up
    |> |> to 2098x1311 for odd formats. 2048x1152 (non-standard, but sensible)
    |> |> format
    |> |> would also be doable on single link. Dual link could go up to 2960x1850.
    |> |
    |> | Well, at least per the pixel clock limits on both single- and dual-link
    |> | DVI, they sure could. The problem is, though, that the DVI standard
    |> | never included a decent compliance certification test, nor is there any
    |> | good spec on cabling, switches, and the like that would truly ensure
    |> | that you can run full rates over any given comibination of such things.
    |> | So as you approach the top-end clock spec, some will work, and
    |> | some may not.
    |>
    |> I called one of the makers of one of the switches I found like this (Blackbox)
    |> and the guy I talked to tried to convince me that no one uses 1920x1200. My
    |> response was "but they do use 1600x1200 when monitors of that type are rare
    |> adn hard to find and are about to go out of production because the world is
    |> shifting to widescreen so they have enough space to display 1920x1080 video?".
    |> He didn't have an answer to that loaded question. I suggested he have the
    |> product sent back to engineering.
    |
    | This monitor is 1920x1200. It is quite common for 24" LCD monitors.

    So when will the KVM switch manufacturers understand that 1920x1200 is a common
    desktop display resolution?

    I found something in another model KVM switch that might indicate some possible
    support issues. It seems many of these KVM switches have an on screen display
    (the "OSD" feature). The switch will have to process the video, syncronize to
    it, and insert their own video, to get that OSD to work. Their logic board
    might not have the capability for some of the higher modes.

    I don't need or care for OSD. I'd even prefer to not have it at all, for a
    desktop environment.
     
  14. Guest

    | In article <>,
    | says...
    |> | In article <>,
    |> | says...
    |> |> What aspects of a DVI switch (KVM for example) would affect its ability to
    |> |> handle higher video modes such as 1920 x 1200 (when it can handle 1600 x 1200)?
    |> |> I'm curious why there are so many DVI switches that have a 1600 x 1200 limit
    |> |> and can't do 1920 x 1200.
    |> |
    |> | What refresh rate? Perhaps it needs Dual Link DVI (DVI-DL) to get
    |> | the refresh rate you're looking for at 1920x1200.
    |>
    |> 1920x1200 (WUXGA) is a single link format. Single link can go all the way up
    |> to 2098x1311 for odd formats. 2048x1152 (non-standard, but sensible) format
    |> would also be doable on single link. Dual link could go up to 2960x1850.
    |
    | At 60Hz, yes. By 85Hz single link is out of gas. That was my point
    | ("what refresh rate?"). Do follow along.

    I will push the refresh rate as low as I can make it work. The lowest monitor
    found will go down to 48 Hz (from HP). If I stick to the literal WUXGA format,
    then it's 60 Hz. For the computers outputting the 1920x1200, the vertical rate
    isn't much of an issue. The analog computers will be outputting some lower
    resolution to be scaled up, and at the lowest refresh rate I can get (because
    that gives me some more resolution on those).
     
  15. krw

    krw Guest

    I suspect it's an excuse to cover for insufficient product planning
    (they didn't see the price falling through the floor on these things
    - $270 last fall).
    Certainly possible. I've had to insert some DVI logic into the
    design I'm working on. The information out there certainly isn't
    clear. It's possible they never tested on larger formats,
    neglecting them because they didn't see them coming so soon.
    I don't want the switch to insert anything, for sure.
     
  16. krw

    krw Guest

    I don't think I'd care too much for 48Hz, though have never tried
    it. My laptop/24" monitor combination is restricted to 60Hz (at
    1920x1200). I thought it was because this is a cheap monitor (which
    I suppose is true - single link).
    "Analog computers"? "Scaled up"? I don't understand the entire
    paragraph.
     
  17. Guest

    | In article <>,
    | says...
    |> | In article <>, phil-news-
    |> | says...
    |> |> |
    |> |> | |> |> | \
    |> |> |>
    |> |> |> 1920x1200 (WUXGA) is a single link format. Single link can go all the way
    |> |> |> up
    |> |> |> to 2098x1311 for odd formats. 2048x1152 (non-standard, but sensible)
    |> |> |> format
    |> |> |> would also be doable on single link. Dual link could go up to 2960x1850.
    |> |> |
    |> |> | Well, at least per the pixel clock limits on both single- and dual-link
    |> |> | DVI, they sure could. The problem is, though, that the DVI standard
    |> |> | never included a decent compliance certification test, nor is there any
    |> |> | good spec on cabling, switches, and the like that would truly ensure
    |> |> | that you can run full rates over any given comibination of such things.
    |> |> | So as you approach the top-end clock spec, some will work, and
    |> |> | some may not.
    |> |>
    |> |> I called one of the makers of one of the switches I found like this (Blackbox)
    |> |> and the guy I talked to tried to convince me that no one uses 1920x1200. My
    |> |> response was "but they do use 1600x1200 when monitors of that type are rare
    |> |> adn hard to find and are about to go out of production because the world is
    |> |> shifting to widescreen so they have enough space to display 1920x1080 video?".
    |> |> He didn't have an answer to that loaded question. I suggested he have the
    |> |> product sent back to engineering.
    |> |
    |> | This monitor is 1920x1200. It is quite common for 24" LCD monitors.
    |>
    |> So when will the KVM switch manufacturers understand that 1920x1200 is a common
    |> desktop display resolution?
    |
    | I suspect it's an excuse to cover for insufficient product planning
    | (they didn't see the price falling through the floor on these things
    | - $270 last fall).

    That well could be. Given the response I got from the rep at Blackbox, that
    would be consistent.


    |> I found something in another model KVM switch that might indicate some possible
    |> support issues. It seems many of these KVM switches have an on screen display
    |> (the "OSD" feature). The switch will have to process the video, syncronize to
    |> it, and insert their own video, to get that OSD to work. Their logic board
    |> might not have the capability for some of the higher modes.
    |
    | Certainly possible. I've had to insert some DVI logic into the
    | design I'm working on. The information out there certainly isn't
    | clear. It's possible they never tested on larger formats,
    | neglecting them because they didn't see them coming so soon.
    |
    |> I don't need or care for OSD. I'd even prefer to not have it at all, for a
    |> desktop environment.
    |
    | I don't want the switch to insert anything, for sure.

    We sure agree on that. At least for a desktop situated KVM switch box, lights
    on the box can do the job better at less cost. It's just a matter of passing
    all the signals fully and not having mechanical contacts to do it.

    I have found this _expensive_ KVM switch that looks like it might do the job
    I need:

    http://www.avocent.com/SwitchViewSC_DVI_4-port.aspx

    The thing is designed for classified environments which require isolation
    between the 4 (or more for larger models) computer connections. OTOH, maybe
    that will end up with a better impedance matching of the signals, and better
    RFI shielding, resulting in less double-edging on analog and fewer errors in
    marginal conditions on digital (such as me hitting the transmit key on my 2m
    HT too near the computer). Still, $500+ for a 4-port KVM? Ouch!
     
  18. Guest

    | In article <>,
    | says...
    |> | In article <>,
    |> | says...
    |> |> | In article <>,
    |> |> | says...
    |> |> |> What aspects of a DVI switch (KVM for example) would affect its ability to
    |> |> |> handle higher video modes such as 1920 x 1200 (when it can handle 1600 x 1200)?
    |> |> |> I'm curious why there are so many DVI switches that have a 1600 x 1200 limit
    |> |> |> and can't do 1920 x 1200.
    |> |> |
    |> |> | What refresh rate? Perhaps it needs Dual Link DVI (DVI-DL) to get
    |> |> | the refresh rate you're looking for at 1920x1200.
    |> |>
    |> |> 1920x1200 (WUXGA) is a single link format. Single link can go all the way up
    |> |> to 2098x1311 for odd formats. 2048x1152 (non-standard, but sensible) format
    |> |> would also be doable on single link. Dual link could go up to 2960x1850.
    |> |
    |> | At 60Hz, yes. By 85Hz single link is out of gas. That was my point
    |> | ("what refresh rate?"). Do follow along.
    |>
    |> I will push the refresh rate as low as I can make it work.
    |
    | ???

    I don't need the refresh rate. I'm not doing fast action gaming. My use of
    computers is programming, building Linux pseudo-distros, and managing some
    web servers. While I would use 75 Hz refresh on a CRT to avoid flicker, I
    don't need to do that on LCD. I have no need to run it even as high as 60 Hz.
    24 Hz would be fine by me if I could find a monitor that would accept it.


    |> The lowest monitor
    |> found will go down to 48 Hz (from HP). If I stick to the literal WUXGA format,
    |> then it's 60 Hz. For the computers outputting the 1920x1200, the vertical rate
    |> isn't much of an issue.
    |
    | I don't think I'd care too much for 48Hz, though have never tried
    | it. My laptop/24" monitor combination is restricted to 60Hz (at
    | 1920x1200). I thought it was because this is a cheap monitor (which
    | I suppose is true - single link).

    At 48 Hz, the DVI clock rate can go lower, compared to 60 Hz, for the same
    geometry (e.g. 1920x1200 on each). The clock rate for 1920x1200 at 60 Hz
    could do 2048x1280 at 52.75 Hz. Or it could do 2560x1600 at 33.75 Hz. You
    just need components (video driver, video card, KVM switch, monitor) that
    don't insist the video mode match one of the named VESA standard modes.



    |> The analog computers will be outputting some lower
    |> resolution to be scaled up, and at the lowest refresh rate I can get (because
    |> that gives me some more resolution on those).
    |
    | "Analog computers"? "Scaled up"? I don't understand the entire
    | paragraph.

    Sorry for the confusion.

    By "analog computers" I meant "The two computers I have here that output their
    video in analog as RGB over a HD-15 connection" ... as opposed to the "digital
    computers" which are "the (other) two computers I (will) have here that output
    their video in digital as RGB over a DVI connection".

    The computers that output video in analog won't be at 1920x1200. They may be
    at 1440x900. I'll live with the upscaling artifacts. They are currently
    running at 1200x960 into a 1280x1024 monitor. The catch is that the highest
    number of video lines I can program into them is 1023. That and I cannot find
    a newer video card that supports the software I use on those machines (maybe
    in the near future the ATI Radeon ones will have enough info released I could
    upgrade the software for).

    Two new computers (one is built now, but I have not selected the video card
    to go to 1920x1200 for it, yet, so it's limping along as a server for now at
    a video geometry of 1152x864) will become my new primary graphical desktops.
    The intention is to go with 1920x1200 but I'm open to doing 2048x1280 or even
    2560x1600 if I can find a monitor that will do it at a slow enough speed to do
    it over ONE DVI link channel. Some monitors will go down to 50 Hz or 48 Hz,
    so it's just a matter of finding one with 2048x1280.

    BTW, that's another of my common rants ... monitors that have LOW frequency
    limits on vertical video frame rates that are higher than an existing standard
    video frame rate (e.g. 23.976 Hz). They just need to have a clock that can
    be adjusted to a lower rate and firmware that doesn't assume all video is at
    a higher rate.

    Have a look at the tech specs on THIS monitor:

    http://pro.jvc.com/prof/attributes/features.jsp?model_id=MDL101671

    It is intended for broadcast studio purposes, but can be used as a computer
    display (as can so many TVs out there). It does support 23.976 Hz in the
    3xBNC component inputs. But it doesn't support 23.976 Hz in the HD15/VGA
    input. I don't see why it shouldn't, though. Apparently it can do the
    component in either YPbPr or RGB, so I'm curious how well it would do if
    I used a VGA to 3xBNC connector to feed the computer video that way.

    I know that going FASTER is hard to do. It requires better clocks and faster
    digital circuits. It requires analog amps with a higher bandpass. But why
    is going _slower_ hard to do, too?
     
  19. krw

    krw Guest

    When I was using a KVM I had it stuck under the table (until the
    hot-key recognition started screwing up). I never needed to look at
    it.
    Ouch. I'd go with a virtual terminal sort of setup first. I have
    two sets of displays now so (when both systems were operational) I
    just switched the keyboard and mouse. If I could put another
    display on my laptop (can't get the graphics card to work in the
    dock) I'd be back to a KVM of some sort. It'll be a while though.
    The desktop system isn't working and I have no time (or interest) in
    "fixing" it at least until we move.
    Don't do that! Ouch indeed. Way north of even my considerable toy
    budget.
     
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