On 04/09/2020 21:31, NY wrote:
> I've got a Pi 3B+ and I'm thinking of upgrading to a 4B, partly to free
> up the Pi 3 to do other tasks.
>
> I've got a couple of questions?
>
> - Can a "system disk" SD card (ie the same disk image) for 3B+ be used
> for a 4B?
As long as you've got the latest updates, you can just move the SD Card
over.

> Is it a case of "yes, but you won't be making full use of the
> 4's 64-bit architecture and larger RAM"?  I'm being lazy and avoiding
> installing and configuring everything all over again unless I have to ;-)

I'd still stick with the Raspbian 32 bit userland until 64 bit OS's
support everything such as GPU accelaration and GPIO libraries.

You can run the normal 32 bit userland with the 64 bit kernel, by adding
one line in config.txt You can then install raspbian-nspawn to run 64
bit applications alongside 32 bit ones.

> - I've read reports of the Pi 4 running quite hot and needing a cooling
> fan, as opposed to just passive heatsinks, when used in a case.

You don't need a fan, the large passive heatsink cases work well. I've
got one Pi 4B with that, and one with a fan case. The latter runs
cooler, but the former is well within spec idling at 45C and going up to
65C under load.

> I'd be using it for recording TV (using external USB DVB decoders) to a
> spinning disk (*) (not to the SD card), using TVHeadend, for SMB-sharing
> folders which are accessed by Windows PCs, and maybe also for running
> simple software such as a browser or an email client. On my 3B, the CPU
> usage is barely measurable for recording from three different sources
> simultaneously, while serving one of the video files to a Windows
> client,

That shouldn't change.

> but it shoots up to nearly 100% as soon as I run Firefox or
> Chromium, even when a static page has been loaded. Is it a known problem
> with the Pi 3 (maybe fixed on the Pi 4) that browsers tend to hog the CPU?

You'll see a massive difference using web browsers thanks to the extra
memory and processor speed. Browsers that use separate tasks for each
tab can make use of all that extra memory even though they are 32 bit.

---druck

--- SoupGate-Win32 v1.05