I have an EPYC 7742 with 128 gig ram. When I added virtualbox (now required I guess) now I only get 16 tasks, the machine is almost idle. What needs to be done to fix this ?

Running cinnamon mint 19 (ubuntu Linux)

There *IS* a way to make this work, but it's complicated. Two ways, actually.

As others have said, the tasks are set up such that BOINC must provide 7.5 GB of memory for each task. They don't actually need that much, and don't actually use that much. If, for example, you recompiled BOINC and turned off that restriction (which is something you CAN do), the tasks would all run just fine.

If you're not a programmer and don't want to change the BOINC software, what you can do is Google the instructions for running multiple BOINC instances on the same computer. Instead of running the normal single BOINC instance, run 8 instances. Each instance will think it's running on a computer with 128 GB. Each of the 8 instances will therefore be able to run 16 tasks. Set the memory limits in the preferences to 100%.

It's a nuisance to do. You have to change cc_config.xml to enable multiple BOINC clients. You have to explicitly start each BOINC instance on a different port number. You have to control each instance individually, again using that unique port number. Finally, if you use WUProp, you need to tell it about the port number with app_config.xml. You should probably also set each instance to use 12.5% of the CPU in case regular tasks are available. (6.125% if the CPU is hyperthreaded and has 256 threads).

EDIT: It would, of course, just be much easier if the project lowered the memory limit. It's just a single setting in the work generator and won't affect how the tasks actually run. I'm not privy to the thought process of the admins, nor am I aware of all the facts, but I'd guess the odds are 50/50 that they lower the memory requirements to something more reasonable at some point. 500 MB seems reasonable to me, based on what I've seen.

I have an EPYC 7742 with 128 gig ram. When I added virtualbox (now required I guess) now I only get 16 tasks, the machine is almost idle. What needs to be done to fix this ?
Running cinnamon mint 19 (ubuntu Linux)

Ooops,
Back to to Python ram calculator again ;) . so 128 cpu/threads X 7.45GB Hmm that's a cool 953.6 giblets of rambo
If you want to keep all of its 128 cpu/threads busy you will have to fit an entire TERABYTE of ram, utterly nuts . . . . .
{nice system :}
there is another AMD EPYC 7742 at `top hosts` position 106 that does have a terrible bite of RAM,
But its still stuffed for running full on coz its got 256 cpu/threads to play with . . . . .
That would help keep the house warm
Don't fancy the lecky bill though :}