Someone on the plus4 list asked how the addition and subtraction of invalid operands works in decimal mode. I got this interesting follow-up to my answer. Marko ---------- Forwarded message ---------- Date: Tue, 25 Jul 2000 12:14:23 +0200 From: Tim Böscke <t.boescke@tu-harburg.de> Reply-To: plus4@c64.rulez.org To: plus4@c64.rulez.org Subject: Re: ADC - SBC > > 1. What exactly happens when I am trying to add a number to a non- > > decimal coded number (semi-tetrade?) in decimal mode. > > I investigated this in 1993 or so. The results are documented in a file > "64doc" that you can find e.g. on ftp.funet.fi. The document includes a Did you ever want to know how it really works ? ;) Check out the patent on it: http://www.patents.ibm.com/details?pn=US03991307__ The adder was one of the main innovations in the 6502 on hardware level. --this message went through the plus4@c64.rulez.org emailing list--- - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi.
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