So after few weeks of learning, finally managed to fix broken Mac Pro 2006 and get Ubuntu 20.04 working. However I'm now running into a problem as only 2GB is showing in my system monitor out of 32GB installed. However on lshw -c memory I'm getting 32gb with all 8 banks of memory being correctly recognized. I also had all 32gb on Lion X. As far as I'm aware this Mac has 64x architecture with 32x EFI. There was some workaround of getting 64 ubuntu installed. Also one of 8 cores is most of the time on 100% when doing nothing. I'm not sure if that has anything to do with it. I have tried taking some of RAM out and rearranging but always ended up with 2gb. I've tried over at ubuntu forum as well but didn't manage to find answer. Thanks!
total used free shared buff/cache available
Mem: 1.9Gi 1.1Gi 268Mi 27Mi 608Mi 685Mi
Swap: 2.0Gi 11Mi 2.0Gi
memory
description: System Memory
physical id: 20
slot: System board or motherboard
size: 32GiB
capabilities: ecc
configuration: errordetection=ecc
dmidecode 3.2
Getting SMBIOS data from sysfs.
SMBIOS 2.4 present.
Handle 0x0020, DMI type 16, 15 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: Single-bit ECC
Maximum Capacity: 64 GB
Error Information Handle: Not Provided
Number Of Devices: 8
total used free shared buff/cache available
Mem: 1.9Gi 1.1Gi 268Mi 27Mi 608Mi 685Mi
Swap: 2.0Gi 11Mi 2.0Gi
memory
description: System Memory
physical id: 20
slot: System board or motherboard
size: 32GiB
capabilities: ecc
configuration: errordetection=ecc
dmidecode 3.2
Getting SMBIOS data from sysfs.
SMBIOS 2.4 present.
Handle 0x0020, DMI type 16, 15 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: Single-bit ECC
Maximum Capacity: 64 GB
Error Information Handle: Not Provided
Number Of Devices: 8