in function didtype of 9/pc/sdiahci.c
        case 0x1002:
                if(p->ccru == 1 || p->ccrp != 1)
                if(p->did == 0x4380 || p->did == 0x4390)
                        sbsetupahci(p);
                type = Tsb600;
                break;

changed to 
	case 0x1002:
		if(p->ccru == 1 || p->ccrp != 1)
		if(p->did == 0x4380 || p->did == 0x4390) {
			sbsetupahci(p);
			type = Tsb600;
		} else if (p->did == 0x4391) {
			sbsetupahci(p);
			type = Tahci;
		}
		break;

as using Tsb600 sets the ahci maximum in function ahcibio to 255. That setting is specific to sb600 SATA controllers (from linux src code) and not to the sb700 SATA controllers.

My SATA controller is and the 8192 works fine
0.17.0:	disk 01.06.01 1002/4391  11 0:0000b001 16 1:0000a001 16 2:00009001 16 3:00008001 16 4:00007001 16 5:fdcffc00 1024
	Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 SATA Controller [AHCI mode]