BusyBox 1.26.2 fdisk applet displays wrong starting CHS values, see example below (RPi3 SD card): Command (m for help): p Disk /dev/mmcblk0: 15 GB, 15636365312 bytes, 30539776 sectors 1272490 cylinders, 3 heads, 8 sectors/track Units: cylinders of 24 * 512 = 12288 bytes Device Boot StartCHS EndCHS StartLBA EndLBA Sectors Size Id Type /dev/mmcblk0p1 27,7,9 232,2,8 8192 69631 61440 30.0M c Win95 FAT32 (LBA) /dev/mmcblk0p2 1023,2,8 1023,2,8 69648 89179 19532 9766K 83 Linux Command (m for help): Looks like StartCHS for second partition is the same as EndCHS
Show your raw partition table (for example, in hexdump form)
See SD card image in the zip http://tinycorelinux.net/8.x/armv6/releases/RPi/piCore-8.1.4.zip
The partition table in piCore-8.1.4.img is as follows struct partition { unsigned char boot_ind; /* 0x80 - active */ unsigned char head; /* starting head */ unsigned char sector; /* starting sector */ unsigned char cyl; /* starting cylinder */ unsigned char sys_ind; /* what partition type */ unsigned char end_head; /* end head */ unsigned char end_sector; /* end sector */ unsigned char end_cyl; /* end cylinder */ unsigned char start4[4]; /* starting sector counting from 0 */ unsigned char size4[4]; /* nr of sectors in partition */ } PACKED; 000001b0: 00 00 00 00 00 00 00 00 4f bf 09 00 00 00 00 07 ........O....... ^^head:7 000001c0: 09 1b 0c 02 08 e8 00 20 00 00 00 f0 00 00 00 02 ....... ........ ^^^^^cyl/sect:0x1b/9=27/9 ^^head:2 ^^head:2 ^^^^^ cyl/sect:0xe8/8=232/8 000001d0: c8 ff 83 02 c8 ff 10 10 01 00 4c 4c 00 00 00 00 ..........LL.... ^^^^^cyl/sect:0x3ff/8=1023/8 ^^head:2 ^^^^^ cyl/sect:1023/8 000001e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 000001f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa ..............U. That's exactly the CHS values fdisk shows.