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BCD Is Wrong on Intel?
- Subject: BCD Is Wrong on Intel?
- From: "Bryan Parkoff" <spam>
- Date: Sat, 17 May 2003 21:58:37 -0500
- Newsgroups: comp.sys.apple2
- Xref: archiver1.google.com comp.sys.apple2:30569
I have reviewed binary coded decimal for Apple II+,//e, and IIgs and
Intel Pentium 3/IV. I have found that BCD does not display the correct
decimal numbers.
I assure that all Apple II models and all 6502,65C02,65816 CPUs have the
correct BCD. Emulator projects for Apple II models are always correct. I
suspect that Intel's 80x86 instruction such as DAA does not display the
correct BCD.
For example. First register is 0x0B and second register is 0x0F. Both
registers should be computerized to show 0x10, but DAA on Intel's CPU shows
0x20. It means that some other BCD numbers will be computized wrong
completely on Intel. It appears to be the fact that Apple II's CPU to be
the correct.
It is possible that Intel's DAA and DAS instrutions are designed wrong
by Intel. Do you think that it should be fixed? Should I notify Intel?
Bryan Parkoff