7 Responses to Reverse Engineering the MOS 6502 CPU 2/6

1. alexandrefournier says:

   December 21, 2010 at 4:20 pm

   @frother Looks like Apple Keynote
2. frother says:

   December 21, 2010 at 5:28 pm

   Does anyone know what presentation program that is?It doesn’t feel like powerpoint
3. MWGrossmann says:

   December 21, 2010 at 6:36 pm

   Little-endian. The correct endian-ness, as everyone knows.
4. Kah7654 says:

   December 21, 2010 at 7:44 pm

   There was the so called "packed BCD" format, where every byte stores two decimal digits. This is usefull for fixed-point decimal arithmetic which in turn is important for financial arithmetics. 32-bit float as used back then were much to imprecise to be used for even simple financial stuff. So the BCD mode had it’s use because it made this much faster.
5. ianhan79 says:

   December 21, 2010 at 8:52 pm

   @thelleht it would have been useful if you were working on a 6502 built in a calculator that went 6502 -> bcd decoder -> 7seg or the such. For a normal desktop computer I can’t see it ever being useful either, I agree.
6. thelleht says:

   December 21, 2010 at 10:00 pm

   @ianhan79 There were BCD instructions in the 68000 too. Can honestly say I literally NEVER used them. I read they even took them out of later versions of the 680×0 series.
7. ianhan79 says:

   December 21, 2010 at 11:08 pm

   BCD was useful for 7seg displays driven by BCD decoders.