Forum Rules and Etiquette

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Zenith-486SX/20E - A Few Questions...

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    Zenith-486SX/20E - A Few Questions...

    Hey people, after working long and hard ive finaly managed to get myself back on with a fully working Zenith 486 Matchine!


    The computer itself is labled the 486/SX20E.. (20) being a 20mhz i presume, after flicking through the manual for the matchine, i found that this isnt the case, the computer was actuly a 33mhz origonaly, however now its fitted with a 50mhz chip on a rizer from the socket... hard to explain, ive never seen anything like it realy..

    The Socket that would normaly seat the CPU has a board slotted into it, then the chip sits on top of that, ive checked to see its an overdrive and thats not the case.. it just rises it up, that and the chip has been upgraded from the SX33 to the SX50 intel... so any information reguarding this particular unit, id greatley appreciate.

    My Questions are...

    1- Does the SX50 Generation CPU require any form of cooling? the chip itself is bare, i knew the SX25's and 33's didnt require cooling, but the DX66's and above did, im not so sure on this 50 tho... any thaughts?

    2- The unit has an offboard IDE controller.. and it the system itself does not have a post screen, just literley boots right into DOS.. did these come with any form of BIOS interface? or was it more basic like the realy old IBM units?

    i think thats about it realy... any information reguarding the unit would be greatley appreciated.

    thanks a bunch

    Last edited by Markj595; August 27, 2011, 11:05 AM.

    1. its not going to hurt, but the last DX-50 system I had, did NOT have a cooler.
    2. bios' are different from manufacturer to manufacturer. If there is no way to change the bios settings, I would take an educated guess and say that there is a floppy boot disk that can change config settings.

    ALSO, dont trash the hard disk! In all likelihood the 33->50 mhz upgrade board may have a special driver. I'd check the config.sys and autoexec.bat real good before I did anything.
    It is a mistake to think you can solve any major problems just with potatoes.


      Agreed a 50 probably doesn't NEED a cooler, but it wouldn't hurt. The riser/stacker is probably a voltage regulator (5v to 3.3v) or clock multiplier.

      As for the BIOS if you can't find the original setup disks, you can try something like GSETUP to set the most basic settings (disk, clock, video).

      I have never seen a PC CPU upgrade that requires a driver (short of driver for enabling cache), but there is a first for everything, not a bad idea to backup regardless.
      My Vintage computer/blog site
      Searching for a keyboard for a WYSEpc WY-1100.


        Originally posted by Markj595 View Post
        The computer itself is labled the 486/SX20E..
        The 'E' designation leads me to believe it's an EISA machine. I have a Zenith 486/25E. Searched my files and found a config file. No guarantee if this will work on your machine, but it can be downloaded from here:
        Last edited by Chuckster_in_Jax; August 27, 2011, 09:21 PM.


          Originally posted by Chuckster_in_Jax View Post
          The 'E' designation leads me to believe it's an EISA machine. I have a Zenith 486/25E. Searched my files and found a config file. No guarantee if this will work on your machine, but it can be downloaded from here:

          If it is an EISA machine the GSETUP I posted earlier probably will not work, its meant for AT class ISA machines, I doubt its EISA aware (and may actually corrupt EISA config if you tried changing setup options, not sure on that, but if you don't have the proper config disk, I wouldn't tempt fate).
          My Vintage computer/blog site
          Searching for a keyboard for a WYSEpc WY-1100.


            From an article on the WEB:

            Zenith Data Systems Inc offers four microcomputers based on the Intel 80486SX processor that are ideal for the intensive demands of today's educational market. Three powerful machines are based on 32-bit 486 processors and operate on a 32-bit EISA architecture. They come with a standard 4Mbytes of memory and IDE hard drives designed to support multitasking and graphics-intensive applications. The Z-486SX/20E and Z-486SX/25E offer the advantages of the original 80486DX processor with the exception of numeric co-processing capability. The lower-end 20E is designed for educators running Microsoft Windows and utilizing the Dynamic Data Exchange (DDE). The 20E has a fast VGA card and open 5.25-inch drive bays to facilitate tape backup or CD-ROM. The 25E combines the 25-MHz 486SX processor and the TI-34010 processor-based TIGA/VGA video card for enhanced graphics performance. The top of the line 33E is designed for processing-intensive applications such as computer-aided drafting and design. It utilizes a 33-MHz 80486DX processor, and offers faster clock speed and an expanded IDE hard disk. The 33ET is designed as a network file server, offering eight open EISA slots and six open drive bays as well as 8Mbytes of memory.


              Thanks for the info guys, i appreciate your time and support with this ... yeah when i get back from work ill have a look at the config and see if anything stands out. ill take some photos too, so you can see how the matchine is built and perhaps the hardware involved, the system indeed is EISA, another question reguarding the ISA infostructure... is it at all possable to install standard ISA soundcards to an EISA? ive got a Astech soundgalaxy Pro 16 ISA new from a matchine years ago.. she never got used because someone donated me a PCI Soundblaster 16. id rarther not try, without knowing if any damage would be done.. thanks again in advance



                The EISA (Extended Industry Standard Architecture) is a superset of the ISA 8-bit and 16-bit architecture. The important features of the EISA specification include:
                * Full compatibility with the ISA standard. ISA 8-bit and 16-bit expansion boards can be installed in EISA slots.