RPi4 to RPi5 upgrades nots on PiDP-10

[Steve Lewis]

I wasn't sure how demanding the PiDP-10 software would be, so I started with the RPi4 64-bit 8GB.   Things ran ok - but if I also wanted to use the RPi to run a browser (like for looking up documentation), I felt a little more performance would be good.

Two main lessons learned to share:

1) The RPi5 runs hotter.  I had heat tape but not really heatsinks.  Using htop (and libsensors5), the RPi5 cores were reporting 85degC! Hot hot.    So I placed a 120mm fan at about a 45deg angle on the right side, to flow air thru the RPi5 at the rear.  Within a few minutes, the temps settled down to ~57degC.  Tad hot but reasonable.    With a couple Knight instances and the Type 340 in action (minsky), temps creep back up to 64-66degC.

To verify this, I turned the fan back off - and within minutes, the temps creped back up to 85degC.   Power the fan back on, and back down to the low 60s, idling around 55-57degC when not really hosting any connections.

2) Sound.  One thing I liked about the RPi4 was the stereo jack.   But then I realized - on the RPi5, you can still get a stereo jack: use the stereo jack on the monitor, with the audio being passed through over HDMI.   That's working fine, the CON TTY sounds great and in sync with the text.   

I haven't tried a USB gamepad yet for spacewar.   And imlac still isn't working for me (runtime issue with missing .so), haven't had time yet to work through how to rebuild it from source.  So I can't vouch for how much power/resources imlac uses.   For some reason I can't close my 340 and cscope window - I believe I could back when I was using RPi4.  I'm not sure whats different with this second install (I can close them with pdpcontrol stop, but not by clicking on the top right window X).  

I can open multiple Knight TV hosts, but only a single VT52.   And I can either do TELECON connection or CON, but not both.   Just noting this, not saying its an issue.

RAM doesn't seem be an issue.  With 340, 2xKnight (tvwar) running stuff, CON, VT52, the RAM is still under 1.5GB.  CON (with audio) is responsive and in sync when log status comes by.  The minsky output is sluggish with all that going (so maybe 4 simulated connections) with all the cores in ntop reporting over 70%.  With the fan on full, temps riding at ~64degC.

So - it would be better to integrate the 120mm fan at the back of the PiDP-10 panel.  I know that's supported, but what I mean is: a functional fan angled at 45deg and maybe a shroud to go over to RPi5.

I'd recommend the RPi5 over the RPi4 on this - but running over 80degC on cores isn't really sustainable for long term.  I'm ok running in the 60's degC under load.

-Steve

[Steven A. Falco]

I use the official active heatsink for my Pi5. It is running at about 54'C while lightly loaded.

Steve

[Luke Shiner]

The RPi5 really does require a heatsink and fan. The official one is cheap and works great, highly recommended. It does have a small issue on the PiDP-10 in that the cover for the RPi doesn't sit perfectly with the heatsink attached due to how it attaches to the Pi. The manual suggests drilling a small hole for it, which is certainly an option. I just let the cover sit a little wonky, it's on the back anyway.

I believe the option for the fans is intended for the audio ambience, I remember reading that the holes were designed to make the fan sound reminiscent of the real PDP-10. They aren't intended for cooling and without a heatsink I don't think they would do much to help in that regard.