douglas5962
Posts: 28
Joined: Thu Mar 29, 2018 2:22 pm

Re: CM3+ Released with up to 32GB eMMC

Fri Feb 01, 2019 1:42 am

Just want to throw it out there that I tried to boot a CM3+ Lite with a Pi-Gen image created on December 8th and it failed to boot. I re-ran Pi-Gen this evening and that new image would actually boot. The strange thing is that the custom cmdline.txt, config.txt and dt-blob.bin files I used in Pi-Gen are all from August 2018.

aBUGSworstnightmare
Posts: 1492
Joined: Tue Jun 30, 2015 1:35 pm

Re: CM3+ Released with up to 32GB eMMC

Sat Feb 02, 2019 8:08 am

From the blog:
Note that due to power-supply limitations the maximum processor speed remains at 1.2GHz, compared to 1.4GHz for Raspberry Pi 3B+.
which power-supply limitations are we talking about exactly?

fruitoftheloom
Posts: 20726
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: CM3+ Released with up to 32GB eMMC

Sat Feb 02, 2019 9:33 am

aBUGSworstnightmare wrote:
Sat Feb 02, 2019 8:08 am
From the blog:
Note that due to power-supply limitations the maximum processor speed remains at 1.2GHz, compared to 1.4GHz for Raspberry Pi 3B+.
which power-supply limitations are we talking about exactly?

AFAIAA

The Raspberry Pi 3B+ has a ""MaxLinear MxL7704 power management IC"" which the Compute Module 3+ does not have...

https://www.raspberrypi.org/blog/pi-power-supply-chip/
Retired disgracefully.....

aBUGSworstnightmare
Posts: 1492
Joined: Tue Jun 30, 2015 1:35 pm

Re: CM3+ Released with up to 32GB eMMC

Sat Feb 02, 2019 4:32 pm

The only voltage which is generated on the Compute Module itself is 1.2V (for Core and Memory).

Questions: is this causing the limitation? All other voltages are supplied/generated externally.
EDIT: Just checked table 8 of both data sheets --> exactly the same.

There is no schematic of CM3+ released so far, so impossible to tell from there what is the limiting factor for 1.2GHz max main clock.

Would be glad if somebody from the foundation could share some insights which explains this limitiation.

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