diff --git a/ubb-vga/physmem.c b/ubb-vga/physmem.c
index af9fb9f..6a75b8c 100644
--- a/ubb-vga/physmem.c
+++ b/ubb-vga/physmem.c
@@ -28,19 +28,24 @@
 #define	PM_SWAPPED	62
 #define	PM_PRESENT	63
 
+#define	ALIGN		32	/* DMA transfer size */
+
 
 static void align_brk(int alignment)
 {
-	unsigned long addr;
+	unsigned long addr, remainder;
 
 	addr = (unsigned long) sbrk(0);
-	sbrk(alignment-(addr % alignment));
+	remainder = addr % alignment;
+	if (remainder)
+		sbrk(alignment-remainder);
 }
 
 
 void **calloc_phys_vec(size_t n, size_t size)
 {
 	void **vec;
+	unsigned long pos;
 	int i;
 
 	vec = malloc(sizeof(void *)*n);
@@ -50,7 +55,10 @@ void **calloc_phys_vec(size_t n, size_t size)
 	}
 
 	for (i = 0; i != n; i++) {
-		align_brk(512);	/* crude page alignment */
+		align_brk(ALIGN);
+		pos = (unsigned long) sbrk(0);
+		if ((pos & ~(PAGE_SIZE-1)) != ((pos+size) & ~(PAGE_SIZE-1)))
+			sbrk(PAGE_SIZE-(pos & (PAGE_SIZE-1)));
 		vec[i] = sbrk(size);
 		memset(vec[i], 0, size);
 	}
@@ -94,7 +102,7 @@ static unsigned long xlat_one(int fd, unsigned long vaddr)
 		abort();
 	}
 	paddr = ((map & 0x7fffffffffffffULL) << pshift) | offset;
-//	fprintf(stderr, "0x%x -> 0x%x\n", vaddr, paddr);
+//	fprintf(stderr, "0x%lx -> 0x%lx\n", vaddr, paddr);
 	return paddr;
 }