Does anyone know how to run older, NO-prefetch boinc-client in 20.04.2 LTS Ubuntu.

When running PrimeGrid it is very important to be first one to return tasks, then you are credited finding prime.

Current repository has 7.16.6 version and that version has task prefetch, so when running tasks which run like 32 sec (in my GTX1650Super GPU, way faster in RTX-series) there is always 5 to 6 tasks Waiting to run, so 3 minutes waiting before they are reported, and that is much when trying to be 1st one.

Problem I have encountered is that older, like 7.4.21 (is that even pre-prefetch?) doesn't run because

error while loading shared libraries: libpng12.so.0: cannot open shared object file: No such file or directory

What I do is know that version of libpng is no longer available in Ubuntu 20...

Does anyone know how to get older version working? Actually get older version of libpng so older versions can run...

Cache is set to zero, and resource share is zero. And "Max # of simultaneous PrimeGrid task" is not answer, after limiting it to 9 I got 4 cpu task (so 4 cores are idle) and 4 GPU tasks are waiting to run...

You'd probably have to build your own binaries from sources, using the build tools and libraries native to your own machine.

You can download that version's source code from https://github.com/BOINC/boinc/tree/client_release/7%2F7.4

You'd probably have to build your own binaries from sources, using the build tools and libraries native to your own machine.

That was the answer I was afraiding... I has been decades since I compiled something... Well, live and learn... again :)

Found another way to install older Boinc, 7.9.3

1. Edit apt sources list, commented all focal (Ubuntu 20.04.2 LTS) repositories, added bionic (Ubuntu 18.05.5) repositories. (had to comment all focal because apt always installed 7.16.6 version)

nano /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu bionic main universe
deb-src http://archive.ubuntu.com/ubuntu bionic main universe
apt update 

2. Installed 7.9.3

apt install boinc=7.9.3+dfsg-5

3. Disabled Boinc auto-update

apt-mark hold boinc

4. Edited apt sources list, reversed edited lines to orignal, updated apt

nano /etc/apt/sources.list
apt update 

3. Disabled Boinc auto-update

apt-mark hold boinc

Didn't work, updated to 7.16.6, now added:

apt-mark hold boinc
apt-mark hold boinc-client
apt-mark hold boinc-manger
apt-mark hold libboinc7

Let's see will it work...

Found another way to install older Boinc, 7.9.3

1. Edit apt sources list, commented all focal (Ubuntu 20.04.2 LTS) repositories, added bionic (Ubuntu 18.05.5) repositories. (had to comment all focal because apt always installed 7.16.6 version)

nano /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu bionic main universe
deb-src http://archive.ubuntu.com/ubuntu bionic main universe
apt update 

2. Installed 7.9.3

apt install boinc=7.9.3+dfsg-5

3. Disabled Boinc auto-update

apt-mark hold boinc

4. Edited apt sources list, reversed edited lines to orignal, updated apt

nano /etc/apt/sources.list
apt update 

You had better go back and RE-EDIT THIS and try again... You spelled BOINC WRONG >>> "bionic" should be "boinc".

boinc is correctly spelled at steps 2 and 3.

The 'bionic' main universe in step 1 is, I suspect, a different animal altogether.

bionic is a version of Ubuntu (18.04 to be precise).
It's not recommended to load older version libraries into a newer Linux version.