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$10 386/486 (Cyrix Cx486DLC installed + math co-processor) adventures

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    $10 386/486 (Cyrix Cx486DLC installed + math co-processor) adventures

    Bought me another computer and this time a 386 system. It currently has a 1.44MB 3.5" FDD, 1.2MB 5.25" FDD, and some size IDE HDD installed along with a generic (possibly a WinBond chip) ISA I/O controller card and some VGA video card.

    Specs of the system:
    Unknown motherboard (will look for any markings to identify the board later on)
    Cyrix Cx486DLC CPU (either 33GP or 40GP)
    Math Co-Processor (might be a Cyrix Cx487DLC, will get a better photo)
    Board has 2 EISA slots, 5 ISA slots, has cache chips populated, 4 sticks of SIMM-30 installed, and a bad clock battery (will do a swap and check for any damage and if there's minimal damage, it'll be easy to fix and do a CR2032 battery swap, but I'll follow traces to install a diode to prevent the charging circuitry from blowing the battery up)

    The system itself was only $10 at a consignment shop close by, which $10 for a 386/486 system is actually a great price (better than eBay prices).

    Going to let the system set out for a while and do some more with it. My plans are to use it as a gaming system with 3 sound cards, plus a CD-ROM drive (proprietary one) to use it as a multimedia system and to play games that are overly speed sensitive for certain MIDI modules and games that were meant for 80386 machines. The Cyrix CPU is a 386 chip (PGA-132 LIF) with 486 instruction sets and 1KB cache.

    Stay tuned for further updates, adventures, and computer lab setup for my older systems.
    Current retro systems:
    386/486DLC, AMS NotePro Plus DSTN
    Packard Bell Pack-Mate 28 Plus
    Toshiba Satellite Pro 410CDT, 2x IBM ThinkPad 380D (both TFT)
    iMac G3/600 Graphite, iMac G4/800 Lampshade
    YouTube channel: https://www.youtube.com/c/RetroPCUser

    #2
    The math co-processor is a CHiPs 387 and the CPU is a Cyrix Cx486DLC-33GP. Battery damage is minimal, so that'll be an easy cleanup and the innards, minus the battery are really clean.
    Current retro systems:
    386/486DLC, AMS NotePro Plus DSTN
    Packard Bell Pack-Mate 28 Plus
    Toshiba Satellite Pro 410CDT, 2x IBM ThinkPad 380D (both TFT)
    iMac G3/600 Graphite, iMac G4/800 Lampshade
    YouTube channel: https://www.youtube.com/c/RetroPCUser

    Comment


      #3
      Originally posted by retro-pc_user View Post
      The math co-processor is a CHiPs 387 and the CPU is a Cyrix Cx486DLC-33GP. Battery damage is minimal, so that'll be an easy cleanup and the innards, minus the battery are really clean.
      You got a fairly rare math coprocessor. C&T wasn't very popular because it was short lived.

      If you want to play speed sensitive games, DLC might not be the best choice. Maybe a standard 386-33 would be better.
      "Will the Highways on the internets become more few?"

      V'Ger XT

      Comment


        #4
        SX or DX? And Intel or AMD?
        Current retro systems:
        386/486DLC, AMS NotePro Plus DSTN
        Packard Bell Pack-Mate 28 Plus
        Toshiba Satellite Pro 410CDT, 2x IBM ThinkPad 380D (both TFT)
        iMac G3/600 Graphite, iMac G4/800 Lampshade
        YouTube channel: https://www.youtube.com/c/RetroPCUser

        Comment


          #5
          Ordered an Intel 386 DX-33 and swapped the 3.5" FDD and cable so that I could use the 3.5" as drive A instead of B. Need to figure out the schematics for this board so that I can solder a diode to the circuitry diode for the CMOS battery (already cut the original trace off from the positive terminal area to prevent shorts/explosions from occurring, but I'll verify to make sure again in case I done messed up). Funny thing is, the BIOS sees the 4.3GB HDD, but DOS begs to differ since LBA doesn't exist on a 386 board unless an enhanced IDE BIOS is used or XT-IDE Universal BIOS.
          Current retro systems:
          386/486DLC, AMS NotePro Plus DSTN
          Packard Bell Pack-Mate 28 Plus
          Toshiba Satellite Pro 410CDT, 2x IBM ThinkPad 380D (both TFT)
          iMac G3/600 Graphite, iMac G4/800 Lampshade
          YouTube channel: https://www.youtube.com/c/RetroPCUser

          Comment


            #6
            And the clock won't keep up. When I power it off, the time is 9 minutes behind (if I leave the system off for 9 minutes) or the settings disappear. I already checked the connections and they are all good.
            Current retro systems:
            386/486DLC, AMS NotePro Plus DSTN
            Packard Bell Pack-Mate 28 Plus
            Toshiba Satellite Pro 410CDT, 2x IBM ThinkPad 380D (both TFT)
            iMac G3/600 Graphite, iMac G4/800 Lampshade
            YouTube channel: https://www.youtube.com/c/RetroPCUser

            Comment


              #7
              Originally posted by retro-pc_user View Post
              And the clock won't keep up. When I power it off, the time is 9 minutes behind (if I leave the system off for 9 minutes) or the settings disappear. I already checked the connections and they are all good.
              Symptomatic of low battery voltage to motherboard chip/s.

              CR2032 = 3 volts, then that will be reduced by the diode. Are you sure that is adequate for your motherboard ?

              Comment


                #8
                Yeah, the CR2032 wasn't sufficient enough. Apparently, the diode drops the voltage by 0.5V-0.58V, which is insufficient and the RTC requires 2.7V-4.5V exactly. I decided to solder a 3x AA battery pack by using a GameBoy DMG-01 rear chassis and the positive terminal from the mainboard of the DMG-01 since the board was dead anyway and soldered two wires: 1 for positive, 1 for negative and got 4.5V at the battery leads and 3.8V at the other end of the diode and to the RTC chip, plus, the capacitors and other points that are on the same circuitry. I soldered the battery pack to the external battery header since that is a safer method and I ran out of spare diodes from other boards that broke in the past.

                I then tested it out and the system is keeping the time, date, and settings. All in all, everything is working properly and I also changed the Sound Galaxy NX Pro H/W address to 240h so that the SAAYM (CMS/GameBlaster Clone + YM-2151 and YM-3012 Stereo DAC) can use the H/W address 220h. The only thing I need is to figure out how to disable the COM2 port so that I can use IRQ3 for the YM-2151 chip for a VGM player software so that I can play some VGM files.
                Current retro systems:
                386/486DLC, AMS NotePro Plus DSTN
                Packard Bell Pack-Mate 28 Plus
                Toshiba Satellite Pro 410CDT, 2x IBM ThinkPad 380D (both TFT)
                iMac G3/600 Graphite, iMac G4/800 Lampshade
                YouTube channel: https://www.youtube.com/c/RetroPCUser

                Comment


                  #9
                  Got COM2 disabled now, received an Intel i386 DX-33 and installed it, yet HIMEM test fails: says unreliable XMS memory at address 00113884. XMS driver not installed. With the Cyrix CPU, no error messages. The RAM itself has gold plated pins, yet the RAM slots are tin plated, which I believe is one of the issues, but I don't think that's the case. The system detects the CPU as an AMD Am386 DX-33 according to NSSI. So I'm not sure if it's because it want an AMD CPU installed or if it's something else I'm missing.

                  I cannot find any jumper settings for the board, so I think it auto detects the CPU, so that shouldn't be an issue and the crystal clock oscillator is 66.67MHz, so it's the right speed.
                  Current retro systems:
                  386/486DLC, AMS NotePro Plus DSTN
                  Packard Bell Pack-Mate 28 Plus
                  Toshiba Satellite Pro 410CDT, 2x IBM ThinkPad 380D (both TFT)
                  iMac G3/600 Graphite, iMac G4/800 Lampshade
                  YouTube channel: https://www.youtube.com/c/RetroPCUser

                  Comment


                    #10
                    I checked for bugs, and sure enough, there is a bug: POPAD bug: ! ERROR ! according to HWiNFO. No bugs in the Cyrix CPU, so maybe that explains the issue there. And there is a bug-free one (double-sigma ΣΣ) out there that I see (SX211 CPU ID marker). Going to order that CPU and some RAM to play it safe. Even MemTest86 won't load as the system restarts after showing the blue screen after the loading MemTest86 text appears.
                    Current retro systems:
                    386/486DLC, AMS NotePro Plus DSTN
                    Packard Bell Pack-Mate 28 Plus
                    Toshiba Satellite Pro 410CDT, 2x IBM ThinkPad 380D (both TFT)
                    iMac G3/600 Graphite, iMac G4/800 Lampshade
                    YouTube channel: https://www.youtube.com/c/RetroPCUser

                    Comment


                      #11
                      I'm kind of scratching my head here; why do you want to replace the Cyrix CPU so badly if it works fine? I doubt there are many games that are speed sensitive in a way that they would fail to run on the Cyrix CPU yet work on a 386/33. I mean, sure, I could see the argument for reverting, say, a 5150 that'd been upgraded with a V-20 back to an 8088 in order to make it run "cycle-counting" games and demos correctly, but is there really anything appropriate for a high-end 386 that's going to fall into that category? The 386/33mhz and the 486/25mhz were practically contemporaries (both announced in 1989, but realistically you probably had to wait until early 1990 to get your 486), which the Cyrix chip slots somewhere in between in terms of performance, and on the other end the 386 went all the way down to the lowly 386SX/16, so it seems unlikely to me there were many games that would fail to run on the Cyrix chip unless it was some really obscure issue with the built-in cache or whatever.
                      My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

                      Comment


                        #12
                        I don't see any point in replacing the CPU either. The Cx486DLC40 supports the full 486 instruction set and, according to Wikipedia, performs similarly to an i486SX/25 or Am386/40. Replacing it with an i386/33 is actually a significant downgrade - both in generation and performance.

                        All 386 contain the POPAD bug. There is no bug-free version. The Cx486DLC is not a 386, so does not have this bug.

                        All 386 with double-sigma are fully 32-bit capable; to my knowledge, this includes all chips faster than 16 MHz. Without double-sigma (i.e. early 16 MHz chips only), there are severe bugs when mixing 16- and 32-bit code. Such chips cannot run Windows 95.

                        The 486 instruction set adds instructions for more fine grained cache invalidation (INVD, INVLPG) and some atomic instructions necessary for decent SMP support. This may very well be the reason that memtest86 doesn't run on your 386.

                        So... I think replacing the CPU is a step in the wrong direction.

                        Comment


                          #13
                          It particularly seems like a step back if the BIOS in the board is properly recognizing the Cyrix chip and has full support for it. I know the upgrade version of the Cyrix 486DLC was sometimes a little finicky and could have some compatibility gotchyas with the cache, but with full BIOS support it should be a perfectly decent CPU and arguably more interesting than a plain 386. I'd sure be thrilled to have found a complete system with one for $10.
                          My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

                          Comment


                            #14
                            Reason for the downgrade is because with the turbo button pressed out to slow the system down more, Police Quest I and II run a bit too fast.
                            Current retro systems:
                            386/486DLC, AMS NotePro Plus DSTN
                            Packard Bell Pack-Mate 28 Plus
                            Toshiba Satellite Pro 410CDT, 2x IBM ThinkPad 380D (both TFT)
                            iMac G3/600 Graphite, iMac G4/800 Lampshade
                            YouTube channel: https://www.youtube.com/c/RetroPCUser

                            Comment


                              #15
                              Considering those are games aimed at XT/AT class machines it might make more sense to look at speed-brake software. Or you might try disabling the 486DLC’s cache, there’s a dos utility to control it if the BIOS doesn’t let you. It doesn’t slow it down much but maybe it’ll make a difference.

                              https://ancientelectronics.wordpress...-cyrix-486dlc/
                              My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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