Interesting... I have encountered this problem only once when I did know the SPI flash was broken and couldn't flash it with the internal programmer.
Could you please attach a verbose log from flashrom?
"flashrom -w /tmp/apu2_v220.127.116.11.rom -p internal:boardmismatch=force -VVV"
It will print a lot of information, consider redirecting it to a file.
It is actually hard to tell. We have encountered such errors in other apu owners reports, typically it was a BSD system and the problem was Core Performance Boost. When it comes to Linux, such MCEs are rather rare, thus it is difficult to say what is the culprit.
The Erro code says it was an instruction fetch error on cache L1 level (exactly the same error as here: https://github.com/pcengines/coreboot/issues/469) so it may be related to the cache/CPU somehow, but no idea what could cause it.
Please refer which slots may be used for USB modems with SIM card slots: https://github.com/pcengines/a…ties.md#apu4a-apu4b-apu4c
If you put the Quectel EC25 to mPCIe1 slot it won't work with SMI slots on the board. Regarding the SIM swap pin, it simply selects the SIM switch behavior. By default SISMWAP pin is in low state which means the SIM cards are "crossed":
- mPCIe2 slot is connected to SIM2
- mSATA slot is connected to SIM1
So basically if you have tried both SIM slots, one of two should work for mPCIe2 slot.
We have some Quectel EC25 I believe and may test something out.
For starters, apu2 does not have integrated graphics so one cannot get VGA output on apu2.
I recall having similar issues with extracting the TinyCore in Linux. Please note that the TinyCore instructions also require to make it bootable with syslinux (the boot flag on the partitions is not enough, syslinux will put a bootloader and MBR to the disk): https://pcengines.ch/howto.htm#TinyCoreLinux
I suspect you have missed these steps thus the stick does not boot. Some reference from syslinux wiki: https://wiki.syslinux.org/wiki…a_Bootable_USB:_For_Linux (the Linux kernel image is already inside TinyCore6.4_2017.tar.bz2 so this step may be omitted)
if you try e.g. a pfSense image (amd64 USB memstick serial) or OPNsense image (amd64 serial), and "dd" it on the stick it will boot out-of-the-box. TinyCore is a very small and lightweight system that is typically used for BIOS updates, but it can be done with any other system actually by installing flashrom on the selected operating system.
The USB boot issue you are observing may have various reasons. Few questions to determine the culprit:
1. What is burned on the stick? Any BSD or Linux installer?
2. Did you configure the serial console for the bootloader on the USB stick?
Most of installers give an output to the VGA only, that is why you may be experiencing "nothing happens when I boot the USB stick".
mPCIe2 slot on apu4d does not have PCIe signals routed there. That is why you cannot use the NVMe or WiFi card there. Refer to page 8 of the schematics: https://pcengines.ch/schema/apu4d.pdf or check out the mPCIe slot capabilities on the documentation page: https://github.com/pcengines/a…APU_mPCIe_capabilities.md
The PCIe signals that are routed to the mPCIe2 slot on apu2 are used for the 4th Ethernet controller on apu4.