
DELL COMPUTER CORPORATION

Precision 486SX/25, 486DX/33, 486DX2/50

Processor          80486SX/80487SX/80486DX/80486DX2
Processor Speed    25/33/50MHz
Chip Set           OPTI
Max. Onboard DRAM  64MB
Cache              64/256KB
BIOS               AMI
Dimensions         330mm x 218mm
I/O Options        Bus mouse port, floppy interface, IDE interface,
                   parallel port, proprietary expansion module, serial
                   ports (2), VGA port
NPU Options        None

[Image]

                                CONNECTIONS

  Purpose                  Location     Purpose                Location

  Internal battery           BAT        Serial port 1             J10
  holder

  Proprietary expansion      EXP        IDE interface LED         J23
  module

  Bus mouse                   J1        Reset switch              J24

  IDE interface               J5        Speaker                   J25

  Floppy drive                J6        Power LED & keylock       J26
  interface

  Parallel port               J8        VGA port                  J27

  Serial port 2               J9

                        USER CONFIGURABLE SETTINGS

                Function                     Jumper          Position

     Monitor type select color or             W1            pins 1 & 2
      monochrome VGA                                          closed

      Monitor type select monochrome           W1            pins 2 & 3
                                                              closed

     CMOS memory normal operation             W2            pins 1 & 2
                                                              closed

      CMOS memory clear                        W2            pins 2 & 3
                                                              closed

     CPU clock source select SYSCLK/1         W3            pins 1 & 2
                                                              closed

      CPU clock source select SYSCLK/2         W3            pins 2 & 3
                                                              closed

     VGA port enabled                         W10           pins 1 & 2
                                                              closed

      VGA port disabled                        W10           pins 2 & 3
                                                              closed

                            DRAM CONFIGURATION

     Size         Bank 0         Bank 1         Bank 2         Bank 3

     1MB         (1) 256K x       NONE           NONE           NONE
                    36

     2MB         (1) 256K x    (1) 256K x        NONE           NONE
                    36             36

     3MB         (1) 256K x    (1) 256K x     (1) 256K x        NONE
                    36             36             36

     4MB         (1) 256K x    (1) 256K x     (1) 256K x    (1) 256K x 36
                    36             36             36

     4MB        (1) 1M x 36       NONE           NONE           NONE

     5MB        (1) 1M x 36    (1) 256K x        NONE           NONE
                                   36

     6MB        (1) 1M x 36    (1) 256K x     (1) 256K x        NONE
                                   36             36

     8MB        (1) 1M x 36   (1) 1M x 36        NONE           NONE

     9MB        (1) 1M x 36   (1) 1M x 36     (1) 256K x        NONE
                                                  36

     10MB       (1) 1M x 36   (1) 1M x 36     (1) 256K x    (1) 256K x 36
                                                  36

     12MB       (1) 1M x 36   (1) 1M x 36    (1) 1M x 36        NONE

     16MB       (1) 1M x 36   (1) 1M x 36    (1) 1M x 36     (1) 1M x 36

     16MB       (1) 4M x 36       NONE           NONE           NONE

     17MB       (1) 4M x 36    (1) 256K x        NONE           NONE
                                   36

     18MB       (1) 4M x 36    (1) 256K x     (1) 256K x        NONE
                                   36             36

     20MB       (1) 4M x 36   (1) 1M x 36        NONE           NONE

     24MB       (1) 4M x 36   (1) 1M x 36    (1) 1M x 36        NONE

     32MB       (1) 4M x 36   (1) 4M x 36        NONE           NONE

     33MB       (1) 4M x 36   (1) 4M x 36     (1) 256K x        NONE
                                                  36

     34MB       (1) 4M x 36   (1) 4M x 36     (1) 256K x    (1) 256K x 36
                                                  36

     36MB       (1) 4M x 36   (1) 4M x 36    (1) 1M x 36        NONE

     40MB       (1) 4M x 36   (1) 4M x 36    (1) 1M x 36     (1) 1M x 36

     48MB       (1) 4M x 36   (1) 4M x 36    (1) 4M x 36        NONE

     64MB       (1) 4M x 36   (1) 4M x 36    (1) 4M x 36     (1) 4M x 36

     CACHE CONFIGURATION

     Size          Bank 0

     64KB        (8) 8K x 8

     256KB      (8) 32K x 8

                        CACHE JUMPER CONFIGURATION

      Size               W4                 W5                 W9

      64KB            pins 2 & 3        pins 2 & 3      pins 2 & 3 closed
                       closed             closed

      256KB           pins 1 & 2        pins 1 & 2      pins 1 & 2 closed
                       closed             closed

                          CPU TYPE CONFIGURATION

       Type               W6                 W7                 W8

     80486SX           pins 2 & 3        pins 2 & 3            Open
                        closed             closed

     80487SX           pins 1 & 2        pins 1 & 2         pins 1 & 2
                        closed             closed             closed

     80486DX           pins 1 & 2        pins 1 & 2         pins 2 & 3
                        closed             closed             closed

             VGA REFRESH CONFIGURATION (800 X 600 RESOLUTION)

       Refresh Rate                 SW1/1                   SW1/2

              56Hz                   Off                     Off

              56Hz                    On                     On

             60Hz                   Off                     On

              72Hz                    On                     Off

             VGA REFRESH CONFIGURATION (1024 X 768 RESOLUTION)

         Refresh Rate                  SW1/3                 SW1/4

            Interlaced                 Off                   Off

                60Hz                    Off                   On

                70Hz                     On                   Off

                72Hz                     On                   On

                        VGA REFRESH CONFIGURATION

                   Refresh Rate                            SW1/5

         31.5Hz horizontal, 60/70Hz vertical               Off

         40Hz horizontal, 75/80Hz vertical (see              On
                         note)

      Note :Use 75Hz for video modes 0 through 10h and 13h. Use 80Hz for
      video modes 11h and 12h.

                            VRAM CONFIGURATION

                 Size                                 Bank 0

                  512KB                               NONE

                    1MB                          (4) 44256 ZIPPs

                         VRAM SWITCH CONFIGURATION

                  Size                                SW1/6

                  512KB                                On

                    1MB                                Off

