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Thread: Doubt about 8087 temperature

  1. #1
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    Default Doubt about 8087 temperature

    Hi, I recently started to "update" my old Amstrad PC1512.

    I expanded the memory to 640KB, purchased a Gotek FDD simulator, flashed with the Flashfloppy firmware, and also got the NEC V30 and a D8087-2 co-processor, being this last one the least necessary of all, but once you start is difficult to stop. Oh I forgot, I'm still waiting for the AdLib replica.

    The V30 was the last to arrive, and after verifying there was nothing burning I started to work with all the new hardware. The point is that after, let's say 10 minutes playing around with Checkit, and successfully detecting both IC correctly, the system didn't respond (or it was just taking its time), and I decided to continue the tests in another moment.

    After shuting down, I touched both the CPU and the 8087, the CPU wasn't even warm, but the co-processor was really hot, in a way you couldn't keep your finger on it (or I'm too sensitive, who knows). The math processor tests were made at the very beginning, and they didn't last too much, I think that the rest of the time the 8087 should be in an idle state, but maybe I'm wrong an it was active all the time even if there were not instructions to work with.

    But even if it was working, can it get so hot in so little time? I still have to test the system, under normal conditions (that means, "not running checkit"). Next time I'll try to measure the actual temperature (datasheet says from 0 to 70), and get a heat sink in case this is a normal situation.

    I would like to know if you think this is just its normal behavior, or I should better take it out from the socket asap. Thanks for reading )

  2. #2

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    are you SURE that's a -2 and not a -3? Remember, the max clock speed goes DOWN as the numbers go up.

    I have had a few of the ceramic-only package 8087's run painfully hot to the point of system lockup, for no real fathomable reason... generally I swap them to another machine where they don't exhibit that behavior using a c-series (brazed ceramic) instead in the offending machines where the D's just don't seem to fly.

    Typically if they're heating up enough to hang the system, a heat sink isn't gonna cut the mustard.
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  3. #3
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    At the time, the 8087 was really pushing the development envelope. Yields were low and the chip was comparatively expensive. That's why vendors rarely offered them as standard equipment. Yes, the early ceramic ones run hot.

  4. #4
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    Thanks for the answers.

    I will check again the IC label, but I'm pretty sure it was a -2. I tested the PC a little big longer, and the system didn't freeze at any moment.

    I (manually) monitored the temperature, and the highest was 60C, always running some games and programs, none of them using the 8087 of course.

    That's my main doubt about the co-processor, is it always working? I mean, I suppose that it's always checking the CPU instructions, and when it finds that there's a particular mathematical operation, it takes the control an does the work for the CPU, but if there's not work for it I thought that it was going to stay idle and cold.

    I have to run that TORUS.BAS program in an endless loop and see what happends

  5. #5
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    Quote Originally Posted by Kalidor View Post
    Thanks for the answers.
    I (manually) monitored the temperature, and the highest was 60C, always running some games and programs, none of them using the 8087 of course.
    That seems reasonable. As others mentioned, 8087 runs fairly hot.

    That's my main doubt about the co-processor, is it always working? I mean, I suppose that it's always checking the CPU instructions, and when it finds that there's a particular mathematical operation, it takes the control an does the work for the CPU, but if there's not work for it I thought that it was going to stay idle and cold.
    8087 is built using the nMOS technology that consumes power even when idle. CMOS ICs, such as NEC V30, consume power mostly when switching states, in other words being active. (CMOS devices built using nanometer CMOS technologies also consume power due to leakage... but that didn't really apply until late 90's Pentium III/Pentium 4 times)...

    I have to run that TORUS.BAS program in an endless loop and see what happends
    I don't think BASIC will use FPU, but I might be mistaken. Run CheckIt instead... I also have a dedicated 8087 stress test utility somewhere. I'll look for it...

  6. #6
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    Now, I feel that the PC is safe, thanks for the everybody's explanations.

    I already used checkit, but it is a very short test and not as visual as the torus.bas I mentioned. I found this video, the program is running under exactly the same hardware I currently have (Amstrad PC1512, V30 + 8087):

    https://www.youtube.com/watch?v=mYJ1IPph4tw

    It's quite interesting as you can see the performance under three different set-ups; 8086 --> 8086 + 8087 --> V30 + 8087

  7. #7
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    Try this one

    87test.zip

  8. #8

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    The Commodore PC20-III can run at three speeds from 4.77 up to 9.54 MHz. The manual says you have to insert an 8 MHz 8087. So I did last weekend. At 4.77 MHz the 8087 already ran quite warm; you can touch it but that is not pleasant. I changed to 9.54 MHz but added a small heatsink and let the whole run for some hours. The 8087 became hot again but my impression was that it was not real hotter than before. A reset showed that the PC20 still detected the 8087. I had nothing else at hand to test it so I'm happy with Dieymir's link.
    Even if it survived this stress test, I'm going to install a small fan above the heatsink.
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  9. #9
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    FWIW, I've had a 8087 in my 1000SX since the late 80's and it's always run very hot.
    Last edited by Agent Orange; April 17th, 2019 at 07:26 AM.
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  10. #10

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    Quote Originally Posted by sergey View Post
    8087 is built using the nMOS technology that consumes power even when idle. CMOS ICs, such as NEC V30, consume power mostly when switching states, in other words being active. (CMOS devices built using nanometer CMOS technologies also consume power due to leakage... but that didn't really apply until late 90's Pentium III/Pentium 4 times)....
    I've heard quite a few CMOS vs NMOS discussions, and I really appreciate CMOS' lower power draw, but..
    This makes me wonder, is this one here really that of an improvement ? Let's think about it.
    Constant temperature vs. temperature that constantly changes (increases and decreases).
    The latter causes a fair amount of stress to the material (expands on heat, shrinks on cold).
    IMHO, it would be healthier if a device runs warm or medium-"hot" over a longer time at a constant level,
    than getting hot from cold during workload and vice versa.

    https://en.wikipedia.org/wiki/Fatigue_(material)
    https://www.sciencedirect.com/scienc...20722503002179
    "Time, it seems, doesn't flow. For some it's fast, for some it's slow.
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