diff -rupN linux-2.6.26/drivers/ata/sata_promise.c linux-2.6.26.sata_promise-limit-sataii-to-1.5Gbps/drivers/ata/sata_promise.c
--- linux-2.6.26/drivers/ata/sata_promise.c	2008-07-14 10:22:36.000000000 +0200
+++ linux-2.6.26.sata_promise-limit-sataii-to-1.5Gbps/drivers/ata/sata_promise.c	2008-07-14 10:31:03.000000000 +0200
@@ -345,6 +345,18 @@ static int pdc_sata_port_start(struct at
 		writel(tmp, sata_mmio + PDC_PHYMODE4);
 	}
 
+	/* hack SControl to limit speed to 1.5Gbps */
+	if (ap->flags & PDC_FLAG_GEN_II) {
+		void __iomem *mmio = (void __iomem *) ap->ioaddr.scr_addr;
+		unsigned int tmp1, tmp2;
+
+		tmp1 = readl(mmio + 0x008);
+		tmp2 = (tmp1 & 0xffffff00) | 0x00000011;
+		writel(tmp2, mmio + 0x008);
+		readl(mmio + 0x008); /* flush */
+		printk("%s(port %u): adjusted SControl from 0x%08x to 0x%08x\n", __FUNCTION__, ap->port_no, tmp1, tmp2);
+	}
+
 	return 0;
 }