Investigate 8080/Z80 differences

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There are some minor differences between 8080 from Z80 that were used to
tell one CPU from another. It is probable that T80 still has some Z80-ish
behaviour even in 8080 mode.

Original issue reported on code.google.com by svof...@gmail.com on 14 Jan 2008 at 12:08

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[deleted comment]

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Two known differences:

1) Parity flag is set on overflow in Z80. This is taken care of in T80 and in 
8080
mode the behaviour seems to be correct;

2) DAA on Z80 works after subtraction. This seems to be left out and T80 behaves
Z80ish in Mode 2.

Original comment by svof...@gmail.com on 14 Jan 2008 at 1:52

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cpu8080.v seems to speak in favour of claim (2). The former is also known to 
have
passed some sort of regression test suite. Conclusion => another butchery 
operation
on T80 is due.

Original comment by svof...@gmail.com on 14 Jan 2008 at 2:05

• Changed state: Started

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MICROCOSM ASSOCIATES  8080/8085 CPU DIAGNOSTIC VERSION 1.0  (C) 1980
http://www.classiccmp.org/dunfield/r/test.asm

Original comment by svof...@gmail.com on 14 Jan 2008 at 4:02

• Changed title: Investigate 8080/Z80 differences

Attachments:

• test.asm

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The test is somewhat bogus for this case. It would not tell a Z80 from 8080.

"Fixed" DAA in Mode 2. The test passes.

Rev. 195

Original comment by svof...@gmail.com on 15 Jan 2008 at 2:20

• Changed state: Verified