HDMI with resolution 2560 x 1440 possible?

Dell documentation states that the U2711 HDMI port is (internally) limited to 1920x1080.

According to this article on Wikipedia, it should be fine if your Acer supports HDMI 1.3.

HDMI version | 1.0-1.2a | 1.3 | 1.4
Maximum signal bandwidth (MHz) | 165 | 340 | 340 [50]
Maximum TMDS bandwidth (Gbit/s) | 4.95 | 10.2 | 10.2
Maximum video bandwidth (Gbit/s) | 3.96 | 8.16 | 8.16
Maximum audio bandwidth (Mbit/s) | 36.86 | 36.86 | 36.86
Maximum color depth (bit/px) | 24 | 48[A]| 48
Maximum resolution over single link at 24-bit/px[B]| 1920×1200p60 | 2560×1600p75 | 4096×2160p24
Maximum resolution over single link at 30-bit/px[C]| N/A | 2560×1600p60 | 4096×2160p24
Maximum resolution over single link at 36-bit/px[D]| N/A | 1920×1200p75 | 4096×2160p24
Maximum resolution over single link at 48-bit/px[E]| N/A | 1920×1200p60 | 1920×1200p60

HDMI 1.3 supports resolution 2560x1600 at 75Hz at 24 bits/pixel, and 60Hz at 30 bits/pixel.

I made my Dell U2711 work at 2560x1440 over HDMI, by pointing xorg.conf to a custom EDID file someone created.

...

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "DELL U2711"
    HorizSync       30.0 – 81.0
    VertRefresh     56.0 – 76.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce 8400M GS"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "TwinView" "0"
    Option         "CustomEDID" "DFP-1: /home/dlawson/u2711/dell_u2721_custom.edid"
    Option         "metamodes" "DFP-1: nvidia-auto-select +0+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection