You didn’t make a mistake. ASRock released an old Socket 754 board but with a newer chipset AMD 760 with SB 710 south bridge.
AMD Socket 754 is the first K8 socket after Slot A. AMD users would most probably still own one of these processors in hand if you haven’t abadon this trusty old processor.
ASRock K8A780LM is powered by AMD 760(780L)+SB710. It is a mATX mainboard. It supports Radeon HD3000 (DX10) and DDR memory.
The K8A780LM is more powerful than the early Socket 754 boards. It comes with a PCI-E X16, SATA 2 ports, HD audio, GbE, D-SUB, DVI-D output. One noticeable feature is the preservation of the parallel port for users who still uses LPT1 for printing.
For those who have old AMD processors, you can probably prolong your processor by ‘upgrading’ it to this board.