What frequency does the DDR2 or DDR3 memory operate on the MitySOM-335x modules¶
The memory clock speed of all DDR2 modules is 266MHz, regardless of the UBoot version.
The memory clock speed of all DDR3 modules can be as high as 400MHz however a UBoot version built on 2-14-2014 (http://support.criticallink.com/gitweb/?p=u-boot-mityarm-335x.git;a=shortlog;h=refs/tags/release_20140214) or newer is required. All version of UBoot older than that use a 303MHz clock speed for the DDR3 memory. The speed is not tied to the AM335x CPU (720, 800 vs 1000).
Ethernet link issues when using Gigabit Phy with 10/100 RJ45 and Magnetics¶
This specific issue does not seem to be caused by the MitySOM module itself but in specific carrier board designs that utilize a Gigabit Phy (i.e. KSZ9031 RGMII) with 10/100 magnetics (only 2 data pairs). In this case customers have reported that some devices (i.e. PC and some network switches) will link 100% but other devices (switches) link 0%.
It was found that in this case the problem was that the phy, ksz9031, was advertising gigabit capabilities. Disabling gigabit advertising resolved the phy connection issues and can be done in both Uboot and the Linux Kernel.
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