diff --git a/src/add-ons/kernel/busses/scsi/ahci/ahci_defs.h b/src/add-ons/kernel/busses/scsi/ahci/ahci_defs.h
index 7e20cfec78..59902f08b4 100644
--- a/src/add-ons/kernel/busses/scsi/ahci/ahci_defs.h
+++ b/src/add-ons/kernel/busses/scsi/ahci/ahci_defs.h
@@ -113,6 +113,62 @@ typedef struct {
 } ahci_hba;
 
 
+typedef struct {
+	uint8		dsfis[0x1c];	// DMA Setup FIS
+	uint8		res1[0x04];
+	uint8		psfis[0x14];	// PIO Setup FIS
+	uint8		res2[0x0c];
+	uint8		rfis[0x20];		// D2H Register FIS
+	uint8		res3[0x04];
+	uint8		sdbfis[0x08];	// Set Device Bits FIS
+	uint8		ufis[0x40];		// Unknown FIS
+	uint8		res4[0x60];
+} fis;
+
+
+typedef struct {
+  union {
+   struct {
+	uint16		prdtl;			// physical region description table length;		
+	uint16		pmp : 4;		// Port Multiplier Port
+	uint16		: 1;
+	uint16		c : 1;			// Clear Busy upon R_OK
+	uint16		b : 1;			// Build In Self Test
+	uint16		r : 1;			// Reset 
+	uint16		p : 1;			// Prefetchable
+	uint16		w : 1;			// Write
+	uint16		a :	1;// ATAPI
+	uint16		cfl : 5;		// command FIS length
+   };
+    uint32		prdtl_flags_cfl;
+  };
+	uint32		ctba;			// command table desciptor base address (alignment 128 byte)
+	uint32		ctbau;			// command table desciptor base address upper
+	uint8		res1[0x10];
+} command_list_entry;
+
+#define COMMAND_LIST_ENTRY_COUNT 32
+
+typedef struct {
+	uint32		dba;			// Data Base Address (2-byte aligned)
+	uint32		dbau;			// Data Base Address Upper
+	uint32		res;
+	uint32		dbc;			// Bytecount (0-based, even, max 4MB)
+	#define DBC_I	0x80000000	/* Interrupt on completition */
+} prd;
+
+
+typedef struct {
+	uint8		cfis[0x40];		// command FIS
+	uint8		acmd[0x20];		// ATAPI command
+	uint8		res[0x20];		// reserved
+} command_table;
+
+
+#define PRD_TABLE_ENTRY_COUNT 168
+
+
+
 extern scsi_sim_interface gAHCISimInterface;
 extern device_manager_info *gDeviceManager;
 extern pci_device_module_info *gPCI;
diff --git a/src/add-ons/kernel/busses/scsi/ahci/ahci_port.cpp b/src/add-ons/kernel/busses/scsi/ahci/ahci_port.cpp
index f9d670a2c2..2200db89c2 100644
--- a/src/add-ons/kernel/busses/scsi/ahci/ahci_port.cpp
+++ b/src/add-ons/kernel/busses/scsi/ahci/ahci_port.cpp
@@ -9,6 +9,7 @@
 
 #include <KernelExport.h>
 #include <stdio.h>
+#include <string.h>
 
 #define TRACE(a...) dprintf("\33[34mahci:\33[0m " a)
 #define FLOW(a...)	dprintf("ahci: " a)
@@ -32,27 +33,35 @@ AHCIPort::Init()
 {
 	TRACE("AHCIPort::Init port %d\n", fIndex);
 
-	size_t size = 999;
+	size_t size = sizeof(command_list_entry) * COMMAND_LIST_ENTRY_COUNT + sizeof(fis) + sizeof(command_table) + sizeof(prd) * PRD_TABLE_ENTRY_COUNT;
 
-	void *virtAddr;
-	void *physAddr;
+	char *virtAddr;
+	char *physAddr;
 
-	fArea = alloc_mem(&virtAddr, &physAddr, size, 0, "some AHCI port");
+	fArea = alloc_mem((void **)&virtAddr, (void **)&physAddr, size, 0, "some AHCI port");
 	if (fArea < B_OK) {
 		TRACE("failed allocating memory for port %d\n", fIndex);
 		return fArea;
 	}
+	memset(virtAddr, 0, size);
 
-	void *virtClbAddr;
-	void *physClbAddr = physAddr;
-	void *virtFisAddr;
-	void *physFisAddr = (char *)physAddr + 1024;
-
-
-	fRegs->clb  = LO32(physClbAddr);
-	fRegs->clbu = HI32(physClbAddr);
-	fRegs->fb   = LO32(physFisAddr);
-	fRegs->fbu  = HI32(physFisAddr);
+	fCommandList = (command_list_entry *)virtAddr;
+	virtAddr += sizeof(command_list_entry) * COMMAND_LIST_ENTRY_COUNT;
+	fFIS = (fis *)virtAddr;
+	virtAddr += sizeof(fis);
+	fCommandTable = (command_table *)virtAddr;
+	virtAddr += sizeof(command_table);
+	fPRDTable = (prd *)virtAddr;
+	
+	fRegs->clb  = LO32(physAddr);
+	fRegs->clbu = HI32(physAddr);
+	physAddr += sizeof(command_list_entry) * COMMAND_LIST_ENTRY_COUNT;
+	fRegs->fb   = LO32(physAddr);
+	fRegs->fbu  = HI32(physAddr);
+	physAddr += sizeof(fis);
+	fCommandList[0].ctba  = LO32(physAddr);
+	fCommandList[0].ctbau = HI32(physAddr);
+	// prdt follows after command table
 
 	return B_OK;
 }
diff --git a/src/add-ons/kernel/busses/scsi/ahci/ahci_port.h b/src/add-ons/kernel/busses/scsi/ahci/ahci_port.h
index ce58406205..631d6384e8 100644
--- a/src/add-ons/kernel/busses/scsi/ahci/ahci_port.h
+++ b/src/add-ons/kernel/busses/scsi/ahci/ahci_port.h
@@ -30,7 +30,12 @@ private:
 private:
 	int						fIndex;
 	volatile ahci_port *	fRegs;
-area_id						fArea;
+	area_id					fArea;
+
+	volatile fis *					fFIS;
+	volatile command_list_entry *	fCommandList;
+	volatile command_table *		fCommandTable;
+	volatile prd *					fPRDTable;
 };
 
 #endif	// _AHCI_PORT_H
diff --git a/src/add-ons/kernel/busses/scsi/ahci/util.c b/src/add-ons/kernel/busses/scsi/ahci/util.c
index 4c4fee4f7c..f3b46cb272 100644
--- a/src/add-ons/kernel/busses/scsi/ahci/util.c
+++ b/src/add-ons/kernel/busses/scsi/ahci/util.c
@@ -40,7 +40,6 @@ alloc_mem(void **virt, void **phy, size_t size, uint32 protection, const char *n
 		ERROR("couldn't get mapping for %s\n", name);
 		return B_ERROR;
 	}
-	memset(virtadr, 0, size);
 	if (virt)
 		*virt = virtadr;
 	if (phy)