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8087 Not Detected?

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    8087 Not Detected?

    I just came cross the "Landmark System Speed Test" and ran it on my XT, which has a V20/8087 combo installed. I had assumed they had been working in Tandem fine, but upon running this software it detected no FPU. I opened the box, made sure the DIP switch was set properly for it (it was) and tried again - sitll no FPU. I tried the DIP switch in the wrong setting, and still no FPU. I have now pulled the 8087 and am curious as to if it were dead to begin with... Should I trust Landmark? Is there any way to tell if it's dead for sure?
    More commonly known as "Yushatak" - www.yushatak.com
    Focused on 486 and Pentium Machines
    I collect All-In-One PCs and Keyboard PCs, especially Compaq.

    #2
    Does Landmark explicitly say 8087: no ? (I can't remember if it does)

    I'm not sure Landmark looks at a coproc at all.
    What about Norton SI or Checkit?
    “Thus, we see that one of the obvious origins of human disagreement lies in the use of noises for words.”

    Comment


      #3
      Unless you do a lot of floating point calculations the co-processor doesn't buy you anything anyway.

      Are you sure you have the co-processor switch on the motherboard in the right position? If I remember correctly, the switch in the "on" position indicates co-processor not installed.

      Comment


        #4
        The switch on the motherboard will only enable/disable the 8087 Interrupt line. If it's enabled, an 8087 interrupt will invoke a NMI.

        Try this FPU diagnosis program by Intel. It will test any x87 from the 8087 to the 487, and it will run on any PC. MCPDIAG.EXE is a text-only version of the diagnostic program only, while RUNMCP.EXE is an EGA/VGA demonstration slideshow including the diagnostic check as one of the options.

        Please note that INSTRUCT.LIB has been splitted into 2 files. It was too big to fit in one >97Kb zip file, so it has to be combined back into one file before it can be used.
        Attached Files
        Current systems owned by me:
        Vintage:IBM PC/XT submodel 087 ( 1983 ), [Kon]tiki-100 rev. C (1983), Compaq Portable I ( 1984 ), IBM PC/XT submodel 078 ( 1985 ), IBM PC/XT286 ( ~1986 ), 3x Nintendo Entertainement Systems ( 1987 ).
        Obsolete:Commodore A500 ( ~1990 ), IBM PS/2 model 70/386 type 8570-161 ( 1991 ), Atari Lynx II ( ~1992 ), Generic Intel 486SX PC ( ~1993 ), AT/T Globalyst Pentium w/FDIV bug MB ( 1994 ), Compaq 486DX4 laptop ( ~1995 ).

        Comment


          #5
          Sorry for not posting this sooner - had a USB fiasco with my main box and couldn't click my USB mouse. Fixed now.. anyway...

          I put the original AMD 8086 back in on a hunch and then ran the software again, and it detects the 8087 and works fine.

          Is it possible that the V20 is damaged in such a way that the only defect is lack of coprocessor compatibility? :P I pulled it from a box that died from corrosive damage, but the chip worked fine in all other respects in my 5160, being rated as equivalent to a 3mhz AT (not too shabby for 4.77mhz XT, heh).

          If it comes down to needing a new V20 I can get one pretty easily at one point from Jameco or some such, but I'd like to know. My V20 is, by the way, an NEC 8750Y5 V20 D70108C -10, which I assume means it's a 10mhz rated model.
          More commonly known as "Yushatak" - www.yushatak.com
          Focused on 486 and Pentium Machines
          I collect All-In-One PCs and Keyboard PCs, especially Compaq.

          Comment


            #6
            Originally posted by Raven View Post
            My V20 is, by the way, an NEC 8750Y5 V20 D70108C -10, which I assume means it's a 10mhz rated model.
            correct

            http://www.x86-guide.com/en/cpu/NEC-8088-4.html
            There are 10 types of people in this world:
            those who understand binary and those who don't. ~Author Unknown

            Comment


              #7
              Originally posted by Neon_WA View Post
              According to that site, it also has four stars of rarity, whatever that means. xD

              Now if I can find myself a 10mhz XT I'm in business with that chip fully.. heh.. not actually in the market for more systems at this second though.
              More commonly known as "Yushatak" - www.yushatak.com
              Focused on 486 and Pentium Machines
              I collect All-In-One PCs and Keyboard PCs, especially Compaq.

              Comment


                #8
                Originally posted by Raven View Post
                I put the original AMD 8086 back in on a hunch and then ran the software again, and it detects the 8087 and works fine.
                The V20 is a 8088 replacement, if you have an 8086 you want the NEC V30 iirc. Perhaps thats the issue.

                IBM 5160 - 360k, 1.44Mb Floppies, NEC V20, 8087-3, 45MB MFM Hard Drive, Vega 7 Graphics, IBM 5154 Monitor running MS-DOS 5.00
                IBM PCJr Model 48360 640kb RAM, NEC V20,, jrIDE Side Cart, 360kb Floppy drives running MS-DOS 5.00
                Evergreen Am5x86-133 64Mb Ram, 8gb HDD, SB16 in a modified ATX case running IBM PC-DOS 7.10

                Comment


                  #9
                  The V20 is documented to work with 8087. If it continues to be a problem for you, I'll check my NEC MicroNOTES--there's something about the 8087 in there, but it's been over 20 years since I looked at them.
                  Reach me: vcfblackhole _at_ protonmail dot com.

                  Comment


                    #10
                    Data width of both chips
                    V20 or 8088 >> 16-bit internal / 8-bit external
                    V30 or 8086 >> 16-bit internal & external

                    8087 >> 16-bit internal & external
                    Last edited by Neon_WA; May 9, 2010, 11:51 PM.
                    There are 10 types of people in this world:
                    those who understand binary and those who don't. ~Author Unknown

                    Comment


                      #11
                      Originally posted by Neon_WA View Post
                      Data width of both chips
                      V20 or 8088 >> 16-bit internal / 8-bit external
                      V30 or 8086 >> 16-bit internal & external

                      8087 >> 16-bit internal & external
                      Sorry, I've got to disagree here. The 8087 is a very different beast. If it sees BHE\ from the CPU high at reset, it reverts to 8 bit transfers (8088/80188 ). Otherwise, it uses 16-bit transfers. It maintains an instruction prefetch queue that exactly mirrors the one in the CPU, as the CPU has to do all of the address computation and manage all of the memory bus cycles.

                      Internally, the 8087 maintains an 84-bit data path in the numeric execution unit.

                      The 8087 is a lot more complex than most people think.
                      Last edited by Chuck(G); May 10, 2010, 10:06 AM.
                      Reach me: vcfblackhole _at_ protonmail dot com.

                      Comment


                        #12
                        Originally posted by lutiana View Post
                        The V20 is a 8088 replacement, if you have an 8086 you want the NEC V30 iirc. Perhaps thats the issue.
                        Arg, yeah, meant to say AMD 8088.
                        More commonly known as "Yushatak" - www.yushatak.com
                        Focused on 486 and Pentium Machines
                        I collect All-In-One PCs and Keyboard PCs, especially Compaq.

                        Comment


                          #13
                          Originally posted by Chuck(G) View Post
                          The V20 is documented to work with 8087. If it continues to be a problem for you, I'll check my NEC MicroNOTES--there's something about the 8087 in there, but it's been over 20 years since I looked at them.
                          Chuck, do you think my V20 is damaged in some way? If not, then perhaps it would be helpful if you perused those notes, otherwise I'll chock it up to a bug/chip damage and not worry about it - use the chip in a system that doesn't need FPU or somethin'.
                          More commonly known as "Yushatak" - www.yushatak.com
                          Focused on 486 and Pentium Machines
                          I collect All-In-One PCs and Keyboard PCs, especially Compaq.

                          Comment


                            #14
                            My feeling is that your V20 is probably screwed up. I have a V30/8087 pair running at 10MHz...no problems there. However, is it possible that older revisions of the 8087 don't get along well with V20/V30? My first attempt at pairing an 8087-1 with my V30 was a complete failure. The 8087 would get really hot and the system would crash often. It was however detected by landmark. That was a C8087-1 (gold top). My current and second attempt is a D8087-1 (ceramic). It works just fine.
                            "Will the Highways on the internets become more few?"

                            V'Ger XT

                            Comment


                              #15
                              Originally posted by Chuck(G) View Post
                              The 8087 is a lot more complex than most people think.
                              According to the instruction set for it on wikipedia.org, it's a lot more complicated than the IBM Technical Reference makes it look. Oh, maybe I have some pages missing or something.

                              Sean

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