A web search led to the solution and now I have the AMD AHCI driver working with the AMD SB700 chipset.
The solution was provided by linhtinh on the AMD forum and involves correcting an error in the amd_sata.inf file. The line below should not begin with a semi-colon.
;HKR, "Parameters\Device","AmdSataPMDisabled",%REG_DWORD%, 0xFF
Delete the semi-colon, save the modified INF file and install the unsigned driver from Device Manager.
For how to install an unsigned driver, see here http://www.howtogeek.com/167723/how...8.1-so-that-you-can-install-unsigned-drivers/
The modified driver must be installed from Device Manager in the following manner. Right click, update driver software, browse my computer for driver software, let me pick from a list of device drivers on my computer then browse to the correct folder and install. Reboot and done.