Questions tagged [binary-coded-decimal]

For questions about the binary-coded-decimal (BCD) numeric representation.

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5
votes
1answer
385 views

What instructions for the 8086 and subsequent x86 CPUs are not available in Long Mode?

I know from this answer that, Modern x86 CPUs are binary compatible with 8086. You can literally run 8086 binaries on a modern PC, in real mode. (The species analogy is a stretch here, but works ...
6
votes
4answers
675 views

Reason behind “ASCII Adjust” instructions being ASCII and not BCD?

I'm just curious if there was ever other instructions that were more ASCII-centric than the CISC associated ones we're left with now? Specifically, all the Binary Coded Decimal (BCD) instructions ...
17
votes
5answers
3k views

Why does the Z80 have a half-carry bit?

The Z80 apparently had a 4-bit ALU, and computes 8-bit values in two stages. The half-carry bit preserves the carry from bits 3 to 4. Why did the designers of this chip choose to preserve that value ...
12
votes
1answer
1k views

What is the relationship between the Ricoh 2A03 and the MOS 6502?

The Ricoh 2A03 (and the 2A07) is the CPU in the well-known Nintendo Entertainment System. Apparently, the die is very similar indeed, as the slides in this video suggest https://www.youtube.com/watch?...