My graphics card has a DVI port and two Display Ports. I have two of the same monitors, one on DVI, one on DP, but can't get xrandr to set the resolution on the DP one. I can't use `xrandr --addmode`

directly to DP-0 without getting an error:

```
Screen 0: minimum 8 x 8, current 1952 x 864, maximum 16384 x 16384
DVI-I-0 connected 1152x864+800+0 (normal left inverted right x axis y axis) 0mm x 0mm
1024x768 60.0 +
1360x768 60.0 59.8
1152x864 60.0*
800x600 72.2 60.3 56.2
680x384 119.9 119.6
640x480 59.9
512x384 120.0
400x300 144.4
320x240 120.1
DVI-I-1 disconnected (normal left inverted right x axis y axis)
DP-0 connected 800x600+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
800x600 60.3*+
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
DP-3 disconnected (normal left inverted right x axis y axis)
1368x768_60.00 (0x33c) 85.2MHz
h: width 1368 start 1440 end 1576 total 1784 skew 0 clock 47.8KHz
v: height 768 start 771 end 781 total 798 clock 59.9Hz
1360x768_60.00 (0x357) 84.8MHz
h: width 1360 start 1432 end 1568 total 1776 skew 0 clock 47.7KHz
v: height 768 start 771 end 781 total 798 clock 59.8Hz
1024x768_60.00 (0x395) 63.5MHz
h: width 1024 start 1072 end 1176 total 1328 skew 0 clock 47.8KHz
v: height 768 start 771 end 775 total 798 clock 59.9Hz
1280x800_60.00 (0x3b3) 83.5MHz
h: width 1280 start 1352 end 1480 total 1680 skew 0 clock 49.7KHz
v: height 800 start 803 end 809 total 831 clock 59.8H
```

Here is the error:

```
$ xrandr --addmode DP-0 1360x768_60.00
X Error of failed request: BadMatch (invalid parameter attributes)
Major opcode of failed request: 140 (RANDR)
Minor opcode of failed request: 18 (RRAddOutputMode)
Serial number of failed request: 35
Current serial number in output stream: 36
```