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Thread: NEC V30 + 8087 @ 10 MHz?

  1. #11
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    NEC did mention the use of a 72091 in some of its literature as an NDP (see, for example, page 6 of the V30 data sheet). I have no idea if that was a CMOS version of the 8087 or just a rebranded 8087--or even if the chip ever made it to production. I can find no vendors offering it. I may have a MicroNote somewhere that also references it.

    Another bit of interest is that the V-series has two coprocessor escape opcodes, (D8 and 66), but I am not aware of any copro that used the second one.

    Altogether, it's a shame that the added V-series instructions were never widely used. Some look to be very useful.

  2. #12

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    I think the sales brochure for the Toshiba T1200 laptop mentions a socket for an 80C87 math coprocessor. No idea if it was just a typo, or perhaps a socket for a product that never materialized.
    "Will the Highways on the internets become more few?"

    V'Ger XT

  3. #13
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    Yeah, it's mentioned in the in the spec sheet under "CPU".

    There are other mentions, but it's hard to determine if those are just typos.

    Finally, there's this. So there may have been a Cyrix 80C87, but I've never seen one.

    If you think about it, complex x86 CMOS came along pretty much after the 80286, so if you were to make a low-power version of the NDP, you'd probably want to start with the 287 or 387.

  4. #14
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    Quote Originally Posted by Chuck(G) View Post
    The V20s and V30s can often be run considerably faster than their labeled rating. I've got a rock-stable system that has an old cerDIP V20 rated for 5MHz that's been running at 9.5MHz for decades. Try it--you're unlikely to harm anything.

    On the matter of the 8087, I'd be less sanguine. Some motherboards allow for running the 8087 at a slower speed than the CPU. Heat is your enemy here.
    I have noticed that the 8087 in my model 25 runs super hot to the touch. Ceramic package. Should I apply a heatsink? I feel like it should be done if I want it to last longer, but it's lasted 30 years without issue.
    IBM PS/2 Model 25, NEC V30 8MHz, 640KB RAM, ATI VGA Wonder XL, 2GB SSD, Ethernet, DR DOS 6/GeOS, Xircom PE3 Ethernet

  5. #15
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    Why bother if it's gone 30 years?

  6. #16

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    Ive often wondered (back in the day)
    why the 80287 wasn’t just made backwards compatible, it was in the same socket with a different pinout

  7. #17
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    If you have a V30, I wonder if the 80c187 could be made to work with some additional logic. Given the limited use, probably not worth the effort.

  8. #18

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    I'd say definitely worth looking into, and always worth the effort!
    "Will the Highways on the internets become more few?"

    V'Ger XT

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    I don't know if I'm supposed to mention it here but I have an intel 8087-2 in excellent shape that has been used slightly with a V-30,
    I just started on the site and if there is a private message feature you can contact me that way...

  10. #20
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    Quote Originally Posted by Chuck(G) View Post
    Why bother if it's gone 30 years?
    I'll go the other way and say that adding a heatsink can never hurt. worst case you're out a little change, best case it makes it last a little longer. Buy a bulk lot of them cheap from China to have in stock. also, 30 years is subjective... the computer was made 30 years ago, but who knows how much use it's gotten. For instance, we know heat eventually kills the SID and PLA on a c64, but they're not all dead yet. On the other hand, it's an 8087 so not integral to the system working (and any benefit of coprocessors on those systems in this day and age could be questionable... very few of us are running old copies of lotus.. haha).
    -- Brian

    Systems: Amstad PCW 8256, Apple IIe/II+/Mac+/Mac 512k, Atari 800/520STFM, Commodore 64/Amiga 3000/PET 4032/SX-64, IBM PS/1 2121-B82, Kaypro II, Osborne 1, Tandy 1000 SX, TI-99/4A, TRS-80 Model 4 GA

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