Hi again.
I tried with a LTS kernel as you suggested. In my case it was 4.19.36-1-lts.
With XFCE, Xorg was using more than 100% according to top and htop. Here the screenshot.
Here again with the tree view
I tested again on kernel 5.0.10-1-ck-bulldozer and it was still high, but not as usual. It was around 65% this time.
Here the tree view
With MATE, Xorg never passes 10% according to top and htop. I tested with both kernels.
Regarding ucode updates. I have run dmesg and I got this
microcode: CPU0: patch_level=0x06000629
microcode: CPU1: patch_level=0x06000629
microcode: CPU2: patch_level=0x06000629
microcode: CPU3: patch_level=0x06000629
microcode: Microcode Update Driver: v2.2.
microcode: CPU3: new patch_level=0x0600063e
microcode: CPU0: new patch_level=0x0600063e
x86/CPU: CPU features have changed after loading microcode, but might not take effect.
x86/CPU: Please consider either early loading through initrd/built-in or a potential BIOS update
There are no new BIOS updates available for my old ASUS M5A78L-M LX PLUS, so I usually ignore that message.
My system hardware is:
H/W path Device Class Description
=======================================================
system System Product Name (To Be Filled By O.E.M.)
/0 bus M5A78L-M LX PLUS
/0/0 memory 64KiB BIOS
/0/4 processor AMD FX(tm)-4100 Quad-Core Processor
/0/4/5 memory 192KiB L1 cache
/0/4/6 memory 4MiB L2 cache
/0/4/7 memory 8MiB L3 cache
/0/2c memory 8GiB System Memory
/0/2c/0 memory 4GiB DIMM Synchronous 1600 MHz (0.6 ns)
/0/2c/1 memory 4GiB DIMM Synchronous 1600 MHz (0.6 ns)
/0/100 bridge RS780 Host Bridge
/0/100/2 bridge RS780 PCI to PCI bridge (ext gfx port 0)
/0/100/2/0 display Tahiti XT [Radeon HD 7970/8970 OEM / R9 280X]
/0/100/2/0.1 multimedia Tahiti HDMI Audio [Radeon HD 7870 XT / 7950/7970]
/0/100/4 bridge RS780/RS880 PCI to PCI bridge (PCIE port 0)
/0/100/4/0 enp2s0 network RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
/0/100/9 bridge RS780/RS880 PCI to PCI bridge (PCIE port 4)
/0/100/9/0 bus VL80x xHCI USB 3.0 Controller
/0/100/9/0/0 usb2 bus xHCI Host Controller
/0/100/9/0/0/1 bus USB2.0 Hub
/0/100/9/0/1 usb3 bus xHCI Host Controller
/0/100/11 storage SB7x0/SB8x0/SB9x0 SATA Controller [IDE mode]
/0/100/12 bus SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
/0/100/12/1 usb5 bus OHCI PCI host controller
/0/100/12.1 bus SB7x0 USB OHCI1 Controller
/0/100/12.1/1 usb6 bus OHCI PCI host controller
/0/100/12.1/1/1 input Usb Mouse
/0/100/12.1/1/3 communication Bluetooth Dongle (HCI mode)
/0/100/12.2 bus SB7x0/SB8x0/SB9x0 USB EHCI Controller
/0/100/12.2/1 usb1 bus EHCI Host Controller
/0/100/12.2/1/3 printer MP280 series
/0/100/13 bus SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
/0/100/13/1 usb7 bus OHCI PCI host controller
/0/100/13.1 bus SB7x0 USB OHCI1 Controller
/0/100/13.1/1 usb8 bus OHCI PCI host controller
/0/100/13.2 bus SB7x0/SB8x0/SB9x0 USB EHCI Controller
/0/100/13.2/1 usb4 bus EHCI Host Controller
/0/100/14 bus SBx00 SMBus Controller
/0/100/14.1 storage SB7x0/SB8x0/SB9x0 IDE Controller
/0/100/14.2 multimedia SBx00 Azalia (Intel HDA)
/0/100/14.3 bridge SB7x0/SB8x0/SB9x0 LPC host controller
/0/100/14.4 bridge SBx00 PCI to PCI Bridge
/0/100/14.5 bus SB7x0/SB8x0/SB9x0 USB OHCI2 Controller
/0/100/14.5/1 usb9 bus OHCI PCI host controller
/0/101 bridge Family 15h Processor Function 0
/0/102 bridge Family 15h Processor Function 1
/0/103 bridge Family 15h Processor Function 2
/0/104 bridge Family 15h Processor Function 3
/0/105 bridge Family 15h Processor Function 4
/0/106 bridge Family 15h Processor Function 5
/0/1 scsi2 storage
/0/1/0.0.0 /dev/sda disk 2TB WDC WD20EARS-22M
/0/1/0.0.0/1 /dev/sda1 volume 1863GiB EXT4 volume
/0/2 scsi3 storage
/0/2/0.0.0 /dev/sdb disk 160GB WDC WD1600AABS-6
/0/2/0.0.0/1 /dev/sdb1 volume 149GiB Windows NTFS volume
/0/3 scsi4 storage
/0/3/0.0.0 /dev/sdc disk 1TB ST1000DM003-1CH1
/0/3/0.0.0/1 /dev/sdc1 volume 4126MiB Linux swap volume
/0/3/0.0.0/2 /dev/sdc2 volume 93GiB EXT4 volume
/0/3/0.0.0/3 /dev/sdc3 volume 833GiB EXT4 volume
/0/5 scsi1 storage
/0/5/0.1.0 /dev/cdrom disk DVD RW AD-7260S
Feel free to ask for any further information. Thanks.