-/* Perform 32*32 bit multiply for 64 bit result, by factoring into 16 bit quantities. */\r
-/* Using an improved algorithm suggested by Steve Green. */\r
- case ID_D_UMTIMES: /* M* ( a b -- pl ph ) */ \r
+/* Assume 8-bit char and calculate cell width. */\r
+#define NBITS ((sizeof(ucell_t)) * 8)\r
+/* Define half the number of bits in a cell. */\r
+#define HNBITS (NBITS / 2)\r
+/* Assume two-complement arithmetic to calculate lower half. */\r
+#define LOWER_HALF(n) ((n) & (((ucell_t)1 << HNBITS) - 1))\r
+#define HIGH_BIT ((ucell_t)1 << (NBITS - 1))\r
+\r
+/* Perform cell*cell bit multiply for a 2 cell result, by factoring into half cell quantities.\r
+ * Using an improved algorithm suggested by Steve Green.\r
+ * Converted to 64-bit by Aleksej Saushev.\r
+ */\r
+ case ID_D_UMTIMES: /* UM* ( a b -- lo hi ) */ \r