!pr0
The Oki 6203 Multiply/Divide Chip..........Bob Sander-Cederlof

If you really need to multiply or divide in a hurry, the Oki 6203 may the ticket.  This device sells for about $7, and can be almost directly connected to the Apple bus.  All you need is one inverter and a prototyping board.

Assuming you built a little card with the device on it, with its two address lines connected to Apple's A0 and A1 lines, you could multiply two 8-bit numbers for a 16-bit product like this:

       MUL.6203 STA SLOT*16+$C080   1ST OPERAND
                STY SLOT*16+$C081   2ND OPERAND
                LDA #2              MULTIPLY COMMAND
                STA SLOT*16+$C083   COMMAND REGISTER
                NOP                 DELAY FOR RESULT
                LDA SLOT*16+$C081   HI-BYTE OF PRODUCT
                LDY SLOT*16+$C082   LO-BYTE OF PRODUCT
                RTS

A very similar program can divide a 16-bit value by an 8-bit value, producing a quotient and remainder.  The time for the multiply is only 22 cycles (plus the JSR and RTS if you make a subroutine), and 24 cycles for the divide.

(Please don't try to order the chip from us, because we don't sell chips.)
