==== //depot/yahoo/ybsd_4/src/sys/i386/i386/machdep.c#8 - /home/peter/ybsd_4/src/sys/i386/i386/machdep.c ====
@@ -1804,6 +1804,35 @@
 	phys_avail[pa_indx] -= round_page(MSGBUF_SIZE);
 
 	avail_end = phys_avail[pa_indx];
+
+	if ((cp = getenv("hw.noclearmem")) != NULL) 
+		return;
+	/*
+	 * Clear all memory outside the message buffer.
+	 * Certain versions of the Tyan 2510 bios do not
+	 * clear extended memory to initialize the ECC system.
+	 */
+	pte = (pt_entry_t)CMAP1;
+	for (i = 0; i <= pa_indx; i += 2) {
+		vm_offset_t end;
+		int *ptr = (int *)CADDR1;
+
+		end = phys_avail[i + 1];
+		for (pa = phys_avail[i]; pa < end; pa += PAGE_SIZE) {
+			/* Do not bzero the kernel... */
+			if (pa >= 0x100000 && pa < first)
+				continue;
+
+			/* Map page into kernel: valid, read/write */
+			*pte = pa | PG_V | PG_RW;
+			invltlb();
+
+			/* Clear the page */
+			bzero(ptr, PAGE_SIZE);
+		}
+	}
+	*pte = 0;
+	invltlb();
 }
 
 void