For comparison, the Zedboard has a 256 megabit (32 megabyte) NOR flash chip. Also, the Zedboard has 512M of ram, via a pair of chips (so they get a 32 bit path to memory). The EBAZ has only a single chip and only 256M of ram.
We see this among the boot messages:
9 ofpart partitions found on MTD device pl35x-nand Creating 9 MTD partitions on "pl35x-nand": 0x000000000000-0x000000300000 : "nand-fsbl-uboot" 0x000000300000-0x000000800000 : "nand-linux" 0x000000800000-0x000000820000 : "nand-device-tree" 0x000000820000-0x000001220000 : "nand-rootfs" 0x000001220000-0x000002220000 : "nand-jffs2" 0x000002220000-0x000002a20000 : "nand-bitstream" 0x000002a20000-0x000006a20000 : "nand-allrootfs" 0x000006a20000-0x000007e00000 : "nand-release" 0x000007e00000-0x000008000000 : "nand-reserve"And when we login, we can do this:
cd /proc cat mtd dev: size erasesize name mtd0: 00300000 00020000 "nand-fsbl-uboot" mtd1: 00500000 00020000 "nand-linux" mtd2: 00020000 00020000 "nand-device-tree" mtd3: 00a00000 00020000 "nand-rootfs" mtd4: 01000000 00020000 "nand-jffs2" mtd5: 00800000 00020000 "nand-bitstream" mtd6: 04000000 00020000 "nand-allrootfs" mtd7: 013e0000 00020000 "nand-release" mtd8: 00200000 00020000 "nand-reserve"So, flash is divided into 9 "chunks". Maybe we could call them partitions, but I am unsure about using that word at this point. Chunk 6 is the root filesystem, as we can see by:
mount /dev/root on / type jffs2 (rw,relatime)So, what is this jffs2? It is a special filesystem created originally for NOR flash devices, but then made to work with NAND flash via the "mtd" device driver. See devices with those names below. It saw general use in OpenWRT.
cd /dev ls -l root lrwxrwxrwx 1 root root 9 Jan 1 1970 root -> mtdblock6 ls -l mtd* crw-rw---- 1 root root 90, 0 Jan 1 1970 mtd0 crw-rw---- 1 root root 90, 1 Jan 1 1970 mtd0ro crw-rw---- 1 root root 90, 2 Jan 1 1970 mtd1 crw-rw---- 1 root root 90, 3 Jan 1 1970 mtd1ro crw-rw---- 1 root root 90, 4 Jan 1 1970 mtd2 crw-rw---- 1 root root 90, 5 Jan 1 1970 mtd2ro crw-rw---- 1 root root 90, 6 Jan 1 1970 mtd3 crw-rw---- 1 root root 90, 7 Jan 1 1970 mtd3ro crw-rw---- 1 root root 90, 8 Jan 1 1970 mtd4 crw-rw---- 1 root root 90, 9 Jan 1 1970 mtd4ro crw-rw---- 1 root root 90, 10 Jan 1 1970 mtd5 crw-rw---- 1 root root 90, 11 Jan 1 1970 mtd5ro crw-rw---- 1 root root 90, 12 Jan 1 1970 mtd6 crw-rw---- 1 root root 90, 13 Jan 1 1970 mtd6ro crw-rw---- 1 root root 90, 14 Jan 1 1970 mtd7 crw-rw---- 1 root root 90, 15 Jan 1 1970 mtd7ro crw-rw---- 1 root root 90, 16 Jan 1 1970 mtd8 crw-rw---- 1 root root 90, 17 Jan 1 1970 mtd8ro brw-rw---- 1 root root 31, 0 Jan 1 1970 mtdblock0 brw-rw---- 1 root root 31, 1 Jan 1 1970 mtdblock1 brw-rw---- 1 root root 31, 2 Jan 1 1970 mtdblock2 brw-rw---- 1 root root 31, 3 Jan 1 1970 mtdblock3 brw-rw---- 1 root root 31, 4 Jan 1 1970 mtdblock4 brw-rw---- 1 root root 31, 5 Jan 1 1970 mtdblock5 brw-rw---- 1 root root 31, 6 Jan 1 1970 mtdblock6 brw-rw---- 1 root root 31, 7 Jan 1 1970 mtdblock7 brw-rw---- 1 root root 31, 8 Jan 1 1970 mtdblock8So in /dev we have 3 ways to get at each "chunk". We have a block device, which is naturally what we use to mount the root filesystem. We also have two raw devices, one read-only and one not.
Tom's Computer Info / tom@mmto.org