How the reset Quartz64-b onboard memory (emmc)

[beepy]

Hello,
Any general help or understanding what is going on here, much appreciated....

I have the Quartz64-b handy.

( [not really relevant]... I tried installing Manjaro's img and it worked 100pc okay.
Then tried https://github.com/jaredmcneill/quartz64_uefi and finally got it's boot menu showing.  - okay)

I then installed ArchLinux Arm and THAT worked - but the onboard ethernet was down (I suspect it's kernel build re a setting should fix it) 
  -did a full pacman -Syu  (and installed a few pkgs)

-I THEN tried plebian and dietPi OS (on a DIFFERENT sdcard)
 and they BOTH cannot boot now (also the Manjaro), complaining the root filesystem is missing.

Has ArchLinux ARM loaded the onboard eMMC (or NRAM etc) with its own /boot/extlinux/extlinux.conf settings?
As -its- root label is 'rootfs' while the others are 'root'

please note: 2 different sdcards, and a clean install of Manjaro / Plebian /DietPi.

Yes, I can provide boot logs, but if anyone knows how to re-flash/re format the onboard eMMC much appreciated.
I cannot see it in /dev, and its not mounted any where

Thank you.

[CounterPillow]

eMMC is on a separate module you have to purchase, if you didn't purchase it you don't have it. Maybe you mean SPI flash, which is present on Model B, but shows up as /dev/mtd*.

Either way, there's two jumpers (J5 and J6) you can set to disable eMMC and SPI flash respectively if I understand the schematic correctly.

In the future please ask support questions like this to the fine and respectable people who told you to flash something onto SPI flash. It's very annoying when people go around telling others to flash their broken stuff to SPI and then leave the support burden to the rest of the community to undo this operation.

[beepy]

eMMC is on a separate module you have to purchase, if you didn't purchase it you don't have it. Maybe you mean SPI flash, which is present on Model B, but shows up as /dev/mtd*.

Either way, there's two jumpers (J5 and J6) you can set to disable eMMC and SPI flash respectively if I understand the schematic correctly.

In the future please ask support questions like this to the fine and respectable people who told you to flash something onto SPI flash. It's very annoying when people go around telling others to flash their broken stuff to SPI and then leave the support burden to the rest of the community to undo this operation.

Thank you CounterPillow for the prompt reply.
Yes, I wasn't sure if my model B has eMMC onboard --it doesn't.
I originally didn't perform anything esoteric -just followed the instructions on the Pine Wiki for installing Arch Arm.

My bad, but the problem turned out to be a faulty SDcard returning:
[    1.466924] mmc0: error -110 reading general info of SD ext reg
[    1.467500] mmc0: error -110 whilst initialising SD card
The nature of the problem meant, although an fsck run and reporting on issues with gpt partitions, something caused the ext4 part not to be available in boot up.

(plebian boots fine now (on a good sd card) but the ethernet is down with dmesg errors)

Thanks again for your time and sorry to disturb you.