
TANDY/RADIO SHACK

486ei 25/SVR

Processor               80486DX
Processor Speed         25MHz
Chip Set                Tandy
Max. Onboard DRAM       64MB
SRAM Cache              256KB
BIOS                    Phoenix
Dimensions              355mm x 304mm
I/O Options             EGA feature connector, floppy drive interface, IDE
                        interface, parallel port, serial port (2), VGA
                        port (on external I/O card)
NPU Options             4167

[Image]

                                CONNECTIONS

  Purpose                   Location    Purpose                  Location

  External battery             J3       Reset switch               W5

  Speaker                     J15       Turbo switch               W6

  Power LED & keylock         J16       Turbo LED                  W7

                        USER CONFIGURABLE SETTINGS

                Function                     Jumper          Position

     CMOS memory normal operation             J2              open

      CMOS memory clear                        J2             closed

     Factory configured - do not alter        W1               N/A

                    SRAM CONFIGURATION

     Size          Bank 0           W3            W4

     256KB      (8) 32K x 8       closed        closed

                         DRAM CONFIGURATION

    Size         Bank 0       Bank 1        Bank 2        Bank 3

     4MB       (4) 1M x 9      NONE          NONE          NONE

     8MB       (4) 1M x 9   (4) 1M x 9       NONE          NONE

    12MB       (4) 1M x 9   (4) 1M x 9    (4) 1M x 9       NONE

    16MB       (4) 1M x 9   (4) 1M x 9    (4) 1M x 9    (4) 1M x 9

    16MB       (4) 4M x 9      NONE          NONE          NONE

    20MB       (4) 1M x 9   (4) 4M x 9       NONE          NONE

    24MB       (4) 1M x 9   (4) 1M x 9    (4) 4M x 9       NONE

    28MB       (4) 1M x 9   (4) 1M x 9    (4) 1M x 9    (4) 4M x 9

    32MB       (4) 4M x 9   (4) 4M x 9       NONE          NONE

    36MB       (4) 1M x 9   (4) 4M x 9    (4) 4M x 9       NONE

    40MB       (4) 1M x 9   (4) 1M x 9    (4) 4M x 9    (4) 4M x 9

    48MB       (4) 4M x 9   (4) 4M x 9    (4) 4M x 9       NONE

    52MB       (4) 1M x 9   (4) 4M x 9    (4) 4M x 9    (4) 4M x 9

    64MB       (4) 4M x 9   (4) 4M x 9    (4) 4M x 9    (4) 4M x 9

                         DRAM SWITCH CONFIGURATION

  Size   SW2/switch    SW2/switch   SW2/switch   SW2/switch    SW2/switch
             1             2            3            4             5

  4MB      closed       closed       closed        closed       closed

  8MB       open        closed       closed        closed       closed

  12MB     closed        open        closed        closed       closed

  16MB      open         open        closed        closed        open

  16MB     closed       closed        open         closed        open

  20MB     closed       closed        open          open         open

  24MB     closed        open        closed         open         open

  28MB      open        closed       closed         open         open

  32MB      open        closed        open         closed        open

  36MB     closed        open         open          open         open

  40MB      open         open        closed         open         open

  48MB     closed        open         open         closed        open

  52MB      open         open         open          open         open

  64MB      open         open         open         closed        open

[Image]

                                CONNECTIONS

  Purpose                   Location   Purpose                   Location

  IDE drive interface         J1       Serial port 2               J5

  Floppy drive interface      J2       IDE interface LED           J6

  Parallel port               J3       VGA feature                 J7

  Serial port 1               J4       EGA feature                 J11

                    SERIAL PORT 1 (J4) CONFIGURATION S1

  Function     Switch    Switch     Switch    Switch    Switch     Switch
                 1         2          3         4         5          6

  disabled      open      open      open      open       open      open

  COM1/IRQ4    closed     open      open      open       open     closed

  COM2/IRQ3     open     closed     open      open      closed     open

  COM3/IRQ4     open      open     closed     open       open     closed

  COM4/IRQ3     open      open      open     closed     closed     open

                    SERIAL PORT 2 (J5) CONFIGURATION S3

  Function     Switch    Switch     Switch    Switch    Switch     Switch
                 1         2          3         4         5          6

  disabled      open      open      open      open       open      open

  COM1/IRQ4    closed     open      open      open       open     closed

  COM2/IRQ3     open     closed     open      open      closed     open

  COM3/IRQ4     open      open     closed     open       open     closed

  COM4/IRQ3     open      open      open     closed     closed     open

                    PARALLEL PORT (J3) CONFIGURATION S2

  Function     Switch    Switch     Switch    Switch    Switch     Switch
                 1         2          3         4         5          6

  disabled      open      open      open       N/A       open      open

  LPT1/IRQ7    closed     open      open       N/A       open     closed

  LPT2/IRQ5     open     closed     open       N/A      closed     open

  LPT3/IRQ7     open      open     closed      N/A       open     closed

                        USER CONFIGURABLE SETTINGS

                 Function                     Jumper         Position

     IOCHRDY signal from pin 27 enabled        J8             open

                                                J9             open

     IOCHRDY signal from pin 21 enabled        J8            closed

                                                J9            closed

     IDE interface pin 34 select PDIAG         J10            open
      signal

      IDE interface pin 34 select ground        J10           closed

     Floppy drive interface                    J12            open
      precompensation mode select 125ns

      Floppy drive interface                    J12           closed
      precompensation mode select 187ns

     IDE interface (J1) enabled                J14           closed

      IDE interface (J1) disabled               J14            open

     On-board video enabled                    J15           closed

      On-board video disabled                   J15            open

     Floppy drive interface (J2)               J16           closed
      interrupt request select IRQ6

      Floppy drive interface (J2)               J16            open
      interrupt request select none

     Single speed motor select                 J17            open

      Dual speed motor select                   J17           closed

     On-board video select 16-bit mode         J18            open
      normal

      On-board video force 8-bit mode           J18           closed

     Floppy drive disk change signal           J19           closed
      enabled

      Floppy drive disk change signal           J19            open
      disabled

     Monitor type select color                 J20          pins 1 & 2
                                                              closed

      Monitor type select monochrome            J20          pins 2 & 3
                                                              closed

      VGA feature connector disabled            J22           closed

      VGA feature connector enabled             J22            open

     Floppy drive interface (J2)               J23           closed
      enabled

      Floppy drive interface (J2)               J23            open
      disabled

     IDE interface (J1) interrupt              J24           closed
      request select IRQ14

      IDE interface (J1) interrupt              J24            open
      request select none

