I am interested, did all Celeron processors support the FCOMIP instruction? I've made a compiler for my programming language and it uses FCOMIP for every floating-point comparison. I've noticed that causes the programs written in my programming language to crash when run on DosBox. So, I am interested how far in the past would I be able to go and still expect the programs my compiler outputs to work on an average computer.

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    The question is a bit borderline for RC.SE, as it is about an active instruction set of not really outdated CPU. I still voted against closing as I thought it's funny to look back at the turning point of the Pentium ... the moment Intel was so sure of them self and their success, that made them loose the market soon after ... cranking up a huge legal machine they to secure their failing monopoly, which as well simply failed, up to a point where they had to licence x86-64 from AMD :) It was a great time for customers.
    – Raffzahn
    Commented Jun 24, 2020 at 19:44
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    This is a good question but nobody's reminiscing about the good old Celeron days yet. I suggest moving it to SO. Commented Jun 25, 2020 at 1:30

1 Answer 1


Short Answer: Yes.

Celeron is a sales name, and does not specify a CPU architecture or instruction set.

Having said that, FCOMIP was introduced with the P6 Family, so essentially with the Pentium PRO (for workstation) and Pentium MMX for mainstream machines. IA-32 implementations before these CPUs do not feature this instruction. The first Celeron is essentially a Pentium II without the secondary cache, so it as well as all later CPUs carrying that name should support FCOMIP.

Compatible CPUs only if they as well support MMX. There were many, but today only AMD, VIA and DMP are left - plus maybe a some virtually unknown embedded implementations:

Other, no longer manufactured models with MMX (and FCOMIP) are:

  • Cyrix 6x86 MX and MII, Cyrix III (now owned by VIA)
  • IBM 6x86 (essentially Cyrix)
  • IDT WinChip, all models, (now owned by VIA)
  • Rise mP6, sold to SIS
  • SIS 550/551 - essentially a Rise mP6 based PC on a single chip (now owned by DMP)

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