Ullrich von Bassewitz wrote: > On Thu, Nov 05, 2009 at 11:12:06PM +0100, Rhialto wrote: >> I don't think so, at least I've never seen one. Even on CPUs that have >> MUltiply intructions in signed and unsigned variants, where you can do >> several narrow MULs to make a wider one, I don't think I've ever seen >> anything other than unsigned multiplications used. > > Thanks. I still think that there must be a way to do it, but ok. It's > unfortunate that working with signed number on the 6502 does always have a > penalty. Even with a signed multiply (e.g., x86 imul), there is a penalty for the sign bit in terms of a few extra logic gates. The function they implement is: result[31:16] <= arg1 ^ arg2; You're basically just doing the same thing in software. There is no shortcut for this. -- Nate Message was sent through the cbm-hackers mailing listReceived on 2009-11-07 01:00:03
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