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I've recently installed Ubuntu 14.04 on my Dell Latitude E4300 and everything is working fine except the Wifi. When I upgraded it to 18.04 the wifi starte working automatically but I can't use 18.04 as it slows my laptop.

I've tried searching in various forums but haven't been able to find a suitable answer. I am new to Ubuntu and attaching some of the outputs that might be helpful.

lspci

00:00.0 Host bridge: Intel Corporation Mobile 4 Series Chipset Memory Controller Hub (rev 07)

00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07)

00:02.1 Display controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07)

00:19.0 Ethernet controller: Intel Corporation 82567LM Gigabit Network Connection (rev 03)

00:1a.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 03)

00:1a.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 03)

00:1a.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 (rev 03)

00:1a.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 03)

00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03)

00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 03)

00:1c.1 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 2 (rev 03)

00:1c.3 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 4 (rev 03)

00:1d.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 03)

00:1d.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 03)

00:1d.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 (rev 03)

00:1d.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 03)

00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev 93)

00:1f.0 ISA bridge: Intel Corporation ICH9M-E LPC Interface Controller (rev 03)

00:1f.2 SATA controller: Intel Corporation 82801IBM/IEM (ICH9M/ICH9M-E) 4 port SATA Controller [AHCI mode] (rev 03)

00:1f.3 SMBus: Intel Corporation 82801I (ICH9 Family) SMBus Controller (rev 03)

02:01.0 FireWire (IEEE 1394): Ricoh Co Ltd R5C832 IEEE 1394 Controller (rev 05)

02:01.1 SD Host controller: Ricoh Co Ltd R5C822 SD/SDIO/MMC/MS/MSPro Host Adapter (rev 22)

0c:00.0 Network controller: Broadcom Corporation BCM4312 802.11b/g LP-PHY (rev 01)





*-network               

       description: Ethernet interface

       product: 82567LM Gigabit Network Connection

       vendor: Intel Corporation

       physical id: 19

       bus info: pci@0000:00:19.0

       logical name: eth0

       version: 03

       serial: 00:21:70:f1:d0:ee

       capacity: 1Gbit/s

       width: 32 bits

       clock: 33MHz

       capabilities: pm msi cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation

       configuration: autonegotiation=on broadcast=yes driver=e1000e driverversion=3.2.6-k firmware=1.7-7 latency=0 link=no multicast=yes port=twisted pair

       resources: irq:27 memory:f6ae0000-f6afffff memory:f6adb000-f6adbfff ioport:efe0(size=32)

  *-network UNCLAIMED

       description: Network controller

       product: BCM4312 802.11b/g LP-PHY

       vendor: Broadcom Corporation

       physical id: 0

       bus info: pci@0000:0c:00.0

       version: 01

       width: 64 bits

       clock: 33MHz

       capabilities: pm msi pciexpress bus_master cap_list

       configuration: latency=0

       resources: memory:f69fc000-f69fffff

  *-network

       description: Ethernet interface

       physical id: 2

       logical name: usb0

       serial: 02:31:3c:0a:06:55

       capabilities: ethernet physical

       configuration: broadcast=yes driver=rndis_host driverversion=22-Aug-2005 firmware=RNDIS device ip=192.168.42.228 link=yes multicast=yes



lspci -knn | grep Net -A3

00:19.0 Ethernet controller [0200]: Intel Corporation 82567LM Gigabit Network Connection [8086:10f5] (rev 03)

    Subsystem: Dell Device [1028:024d]

    Kernel driver in use: e1000e

00:1a.0 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 [8086:2937] (rev 03)

--

0c:00.0 Network controller [0280]: Broadcom Corporation BCM4312 802.11b/g LP-PHY [14e4:4315] (rev 01)

    Subsystem: Dell Wireless 1397 WLAN Mini-Card [1028:000c]



rfkill list all

0: dell-wifi: Wireless LAN

    Soft blocked: no

    Hard blocked: no

1: dell-bluetooth: Bluetooth

    Soft blocked: no

    Hard blocked: no



uname -a

Linux hm-Latitude-E4300 4.4.0-142-generic #168~14.04.1-Ubuntu SMP Sat Jan 19 11:28:33 UTC 2019 i686 i686 i686 GNU/Linux



dpkg -l | grep bcmwl

ii  bcmwl-kernel-source 

6.30.223.248+bdcom-0ubuntu0.2                        

i386         

Broadcom 802.11 Linux STA wireless driver source

I can provide anything else that's required from my end. Any help would be highly appreciated.

In the BIOS I've checked that WiFi is enabled and the switch doesn't do anything. The Wifi catcher is also enabled.

Again I've read a number of threads but can't find a possible solution. So, please provide some help on this.