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I purchased an HDMI to VGA adapter but when I connected the HDMI part to my laptop and the VGA part to my monitor, laptop told me that the optimal resolution for that device was 1024x768 even though I was able to use 1680x1050 when I connected the monitor directly to the VGA socket of my laptop. Somewhere along the line, something caps the maximum resolution I think. Could it be the HDMI socket of my laptop or the HDMI to VGA adapter?

Mateusz Piotrowski
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Gappy Hilmore
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  • Could you edit in what HDMI to VGA adapter you have? HDMI and VGA are fundamentally different, so you need a powered adapter. – TheKB May 21 '16 at 10:37
  • There is no brand name at all on the device. Even the invoice just says hdmi to vga adapter. Lets say this will not work well, would a cheap hdmi to dvi be a problem, since they are just supposed to connect the wires together? – Gappy Hilmore May 21 '16 at 10:47
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    If your monitor supports DVI-D then, yes, an HDMI to DVI adapter will work as well, if not better than VGA. – TheKB May 21 '16 at 10:49
  • An HDMI-to-VGA converter will certainly have a resolution limit, and very likely convert only specific resolutions, e.g. 1024x768, 1280x720p, 1920x1080p. The converter I have uses an EP9851 chip. – sawdust May 21 '16 at 17:34

2 Answers2

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Yes, HDMI to VGA conversion must be limited because VGA standard is limited by the frequency of 400 MHz. This means you cannot get above ex. 2581 * 2581 * 60 Hz = 400 MHz, even if the hardware (RAMDAC) is premium. Usually there is an arbitrary limit because of quality loss already at 1440 and even 1280 lines.

winny
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Frank Sixteen
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    vga works fine when connected directly to the vga output of the laptop, so there can't be anything intrinsic about the vga interface that causes this problem. and a limit of 2581x2581 is certainly good enough. I just purchased a hdmi to dvi cable and it was also able to display the full 1680x1050, so there can't be anything wrong with the hdmi output of the laptop. this can only mean the hdmi to vga adapter had a limit which was not mentioned at all by the vendor. I would be right to be mad at them at this point? – Gappy Hilmore May 21 '16 at 13:10
  • Yes, anything that can't support full HD today is good enough reason to claim and get full refund. I doubt you will find a better HDMI2VGA converter. It is an interface few care to support anymore. You won't have any trouble with HDMI2DVI because they support the same resolution and is in fact electrically the same. DP on the other hand support even higher resolution than HDMI. – Frank Sixteen May 21 '16 at 20:07
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Nothing is infinite, and so both VGA and HDMI will hit a wall sooner or later. But the limit is going to be bandwidth, not resolution (or frequency) per se.

And while HDMI has clear maximum pixel clock defined by the spec of each version (though individual devices may decide to cap to a lower one), there's no such a thing for VGA (in fact there's not even a single document clearly detailing the standard).

The upper bound is just dictated by the quality of the RAMDAC of your graphics adapter. There's unconfirmed legend of some consumer gpu once supporting 500MHz (even though that may have originated from a Windows control panel bug) but in the professional space or with some adapters even 550MHz is not unheard of.

... but back to your case, WSXGA+ (at 60Hz and 8bpc I presume) seems just too low for even the lamest Atom netbook not to support through HDMI. So my bets are on your adapter either having such a pathetically low clock rate to be slower than 1999 DVI, or the thing being too buggy to correctly passthough/convert the EDID of your monitor. In both cases, I'd assume Custom Resolution Utility could help.

mirh
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