diff --git a/src/add-ons/kernel/generic/ata_adapter/ata_adapter.c b/src/add-ons/kernel/generic/ata_adapter/ata_adapter.c
index bd310aa988..b780fdf3f0 100644
--- a/src/add-ons/kernel/generic/ata_adapter/ata_adapter.c
+++ b/src/add-ons/kernel/generic/ata_adapter/ata_adapter.c
@@ -184,22 +184,28 @@ ata_adapter_inthand(void *arg)
 	pci_device *device = channel->device;
 	uint8 statusATA, statusBM;
 
-	// this could be a spurious interrupt, so always read status
-	// register unconditionally to acknowledge those
-	statusATA = pci->read_io_8(device, channel->command_block_base + 7);
-
-	if (!channel->dmaing)
+	if (!channel->dmaing) {
+		// this could be a spurious interrupt, so read status
+		// register unconditionally to acknowledge those
+		pci->read_io_8(device, channel->command_block_base + 7);
 		return B_UNHANDLED_INTERRUPT;
+	}
 
-	// read bus master DMA status to test if the interrupt was
-	// really generated by our controller
+	// need to read bus master status first, because some controllers
+	// will clear the interrupt status bit once ATA status is read
 	statusBM = pci->read_io_8(device, channel->bus_master_base
 		+ ATA_BM_STATUS_REG);
 
+	// test if the interrupt was really generated by our controller
 	if (statusBM & ATA_BM_STATUS_INTERRUPT) {
-		// clear pending PCI bus master DMA interrupt
+		// read ATA status register to acknowledge interrupt
+		statusATA = pci->read_io_8(device, channel->command_block_base + 7);
+
+		// clear pending PCI bus master DMA interrupt, for those 
+		// controllers who don't clear it themselves
 		pci->write_io_8(device, channel->bus_master_base + ATA_BM_STATUS_REG,
 			(statusBM & 0xf8) | ATA_BM_STATUS_INTERRUPT);
+
 		// signal interrupt to ATA stack
 		return sATA->interrupt_handler(channel->ataChannel, statusATA);
 	} else {
@@ -484,6 +490,7 @@ ata_adapter_detect_channel(pci_device_module_info *pci, pci_device *pci_device,
 	uint8 api;
 	uint16 pcicmdOld;
 	uint16 pcicmdNew;
+	uint16 pciVendor;
 
 	SHOW_FLOW0( 3, "" );
 
@@ -539,9 +546,9 @@ ata_adapter_detect_channel(pci_device_module_info *pci, pci_device *pci_device,
 	}
 	if (pcicmdOld != pcicmdNew) {
 		pci->write_pci_config(pci_device, PCI_command, 2, pcicmdNew);
+		TRACE("PCI-ATA: pcicmd changed from 0x%04x to 0x%04x\n", 
+			pcicmdOld, pcicmdNew);
 	}
-	TRACE("PCI-ATA: pcicmd old 0x%04x, new 0x%04x\n", 
-		pcicmdOld, pcicmdNew);
 
 
 	if (supports_compatibility_mode) {
@@ -555,8 +562,16 @@ ata_adapter_detect_channel(pci_device_module_info *pci, pci_device *pci_device,
 			// better were to use a controller lock, but this had to be done in the IDE
 			// bus manager, and I don't see any reason to add extra code for old
 			// simplex controllers
-			TRACE("PCI-ATA: Simplex controller - disabling DMA of secondary channel\n");
-			controller_can_dma = false;
+
+			// Intel controllers use this bit for something else and are not simplex.
+			pciVendor = pci->read_pci_config(pci_device, PCI_vendor_id, 2);
+
+			if (pciVendor != 0x8086) {
+				TRACE("PCI-ATA: Simplex controller - disabling DMA of secondary channel\n");
+				controller_can_dma = false;
+			} else {
+				TRACE("PCI-ATA: Simplex bit ignored - Intel controller\n");
+			}
 		}
 	}