POP CS [BUG?]

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@L.chemist

Joined: 08 Oct 2004
Posts: 14
Location: Russia, Vladimir, Suzdal

@L.chemist 03 Feb 2006, 10:51

HI

according to AMD(Intel) manuals: POP CS has no opcode.
according to FASM: POP CS = 0x0F00.
???

03 Feb 2006, 10:51

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8353
Location: Kraków, Poland

Tomasz Grysztar 03 Feb 2006, 11:13

8086 has "POP CS" = 0xF0. It was removed later (about 186? or 286?) and used as a prefix for extended opcodes instead. fasm includes the instructions for various Intel processors (like not-really-documented LOADALL286/LOADALL386) just in case you needed them.

Though if writing for 8086 in fasm you'd have to very careful with conditional jumps and shifts - I once made special header file for 8086 programming with fasm... where is it? Hmm...

03 Feb 2006, 11:13

@L.chemist

Joined: 08 Oct 2004
Posts: 14
Location: Russia, Vladimir, Suzdal

@L.chemist 03 Feb 2006, 11:38

Tomasz Grysztar wrote:

...I once made special header file for 8086 programming with fasm...

it was(is) good idea

03 Feb 2006, 11:38

MazeGen

Joined: 06 Oct 2003
Posts: 977
Location: Czechoslovakia

MazeGen 03 Feb 2006, 14:19

Tomasz Grysztar wrote:

8086 has "POP CS" = 0xF0. It was removed later (about 186? or 286?).

According to PHG's opcodes.lst file (can be found in Ralf Brown's package), POP CS works on non-CMOS 8086/8088.
BTW, there were a few versions of CMOS 8086 ("80C86"), but what actually means "CMOS 8086"?

03 Feb 2006, 14:19

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