More weird things with Windows 10 guest (after clean install), on two different hosts.
On one host with Windows 10 host, the VoxSVGA + 3D works acceptable.
On the other host with Linux Manajaro (last LTS kernel 5.x) host, the VBoxSVGA (with and without 3D accel) makes the guest to not reach desktop, freezes prior to dots moving, BSOD, etc.
On such other host with Linux Manajaro (last LTS kernel 5.x) host, the VMSVGA with 3D accel makes the guest to not reach desktop, freezes prior to dots moving, BSOD, etc.
On such other host with Linux Manajaro (last LTS kernel 5.x) host, the VMSVGA without 3D accel makes the guest to reach desktop, but so slow that it is unusable, more than half an hour to reach desktop, more than ten minutes to show windows menu after click, more than five minutes to show contextual desktop menu, near two hours to open explorer, near one hour and a half to open notepad, near 45 minutes to open cmd console window, typing the four characters of "CD \" took near two full minutes, listing shown was one character every four or five secons, etc. and near five hours to do a shutdown.
With a lot, lot of patience, i had tried to uninstall, reboot and re-install AddOns, that took a whole week, near 166 hours, but that did not help, still the same.
As i said Windows 10 is a clean install.
The weird thing is that such guest install was done on an Intel Windows 10 host and speed problems appear on an AMD Linux host.
If i install the guest on AMD Linux host it works acceptable, but if i take that guest to the Intel Windows host, then the guest has the exact same problems, BSOD or very slow, depending on (VBoxSVGA with/without 3D and VMSVGA with 3D = BSOD) vs (VMSVGA without 3D = very slow).
Very slow = A lot of minutes (>30 min) to just boot, some hours to do a clean power off, etc
BSOD = Not reach desktop, just freeze or BSOD and auto-reboot.
It happens only with Windows 10 guest, i had tried with and old WinXP guest i had and such worked perfectly on both hosts (i can move the WinXP guest form Intel to AMD back and forth without problems, but not the Win 10 guest).
I also had tested with default settings that VBox uses when creating the VM, with all sorts of combinations (PAE/NX, IO, cache, etc), the only thing that causes any difference on BSOD vs reach desktop is selecting VMSVGA without 3D, but hten that VM is too slow to be able to be used.
Both host have decent modern processor, 8GiB physical RAM (2GiB to guest).
And yes, i had tried with max guest video memory size, no help at all. Also 100%, 90% .. 50% of CPU did not help; guest with only 2 cores so host have plenty of cores extra (Intel is quad core no multi-threaded, AND has 32 cores with 64 threads).
This problems appear after VirtualBox change to 6.x from 5.x, but with 5.x no matter what video configuration i use the win 10 guest BSOD problem was allways appearing if i use the VM guest on AMD if installation was done in Intel and vice-versa, so at least with VBox 6.x i can reach desktop (with 5.x i can not) but it is unusable.