Problem with resolution after updating Lubuntu

Question

I updated Lubuntu (my resolution was working fine before the update) and after the update my resolutions are all skewed up. It only recognizes 1024x768, despite the native resolution being 1280x800. Xrandr doesnt show anything else either, and i know for a fact that the PC supports that resolution cause i ran my windows install on it and it was just fine. My graphic card is a mobility radeon HD3450/3470.

lspci drops this:

Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
BridgeCtl: Parity- SERR- NoISA- VGA+ MAbort- >Reset- FastB2B-
Control: I/O+ Mem- BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O+ Mem- BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
BridgeCtl: Parity- SERR- NoISA- VGA- MAbort- >Reset- FastB2B-
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
BridgeCtl: Parity- SERR- NoISA- VGA- MAbort- >Reset- FastB2B-
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
BridgeCtl: Parity- SERR- NoISA- VGA- MAbort- >Reset- FastB2B-
Control: I/O+ Mem- BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O+ Mem- BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O+ Mem- BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
BridgeCtl: Parity- SERR- NoISA- VGA- MAbort- >Reset- FastB2B-
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O+ Mem- BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] RV620/M82 [Mobility Radeon HD 3450/3470] [1002:95c4] (prog-if 00 [VGA controller])
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-

Answer 1

Lets open up a terminal, press Ctrl+Alt+T.

Now I’m guess if you are using LXDE your default text editor is now Leafpad, so type/copy this:

gksudo leafpad /etc/xdg/lxsession/LXDE/autostart

(if you use a different text editor change leafpad to whatever that may be)

You may be asked for a password as this file is saved as root, enter it and lets move on!

We need to enter find the correct XrandR command, you can find some help in this post about LightDM resolution, or by typing man xrandr to read the documentation.

Here is a sample command:

xrandr --auto --output DVI-1 --primary --mode 1680x1050 --left-of DVI-0

This command does the following

--auto : enables connected devices in their preferred mode
--output DVI-1 : selects the output device to modify
--primary : specifies the selected device as primary
--mode : sets a specific mode for the output device
--left-of DVI-0 : sets position of the devide to “left of” another device (DVI-0)

This command can be added to the end of your opened autostart file, remember to add a @ before the command. Here is my autostart file:

@xscreensaver -no-splash
@lxpanel --profile LXDE
@pcmanfm --desktop --profile LXDE
@/usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1
@xrandr --auto --output DVI-1 --primary --mode 1680x1050 --left-of DVI-0

Now reboot and your resolution should be saved.