TANDY/RADIO SHACK 425SX/T, 433SX/T, 433DX/T, 450DX2/T, 466DX2/T Processor 80486SX/ODP486SX/80487SX/80486DX/ODP486SX/80486DX2 Processor 25/33/50(internal)/66(internal)MHz Speed Chip Set Unidentified Video Chip Set Unidentified Maximum 40MB Onboard Memory Maximum Video 1MB Memory Cache 64/128/256KB BIOS Phoenix Dimensions 330mm x 218mm I/O Options Floppy drive interface, IDE interface, parallel port, PS/2 mouse port, serial ports (2), VGA feature connector, VGA port, riser slot NPU Options None [Image] CONNECTIONS Purpose Location Purpose Location VGA port CN1 Reset switch CN8 Parallel port CN2 External battery J7 Serial port 1 CN3 IDE interface J17 Serial port 2 CN4 Floppy drive interface J18 PS/2 mouse port CN5 VGA feature connector J21 IDE interface LED CN6 Riser slot SL1 Power LED & keylock CN7 USER CONFIGURABLE SETTINGS Function Label Position » Factory configured - do not alter J9 Pins 1 & 2 closed » Factory configured - do not alter J11 Open » Factory configured - do not alter J13 Pins 1 & 2 closed » Factory configured - do not alter J14 Pins 2 & 3 closed » CMOS memory normal operation J20 Closed CMOS memory clear J20 Open » On board video enabled J28 Pins 2 & 3 closed On board video disabled J28 Pins 1 & 2 closed » Factory configured - do not alter J29 Open » Floppy drive write protect J30 Pins 2 & 3 disabled closed Floppy drive write protect J30 Pins 1 & 2 enabled closed » Factory configured - do not alter J31 Pins 2 & 3 closed » Zero wait state enabled J32 Closed Zero wait state disabled J32 Open DRAM CONFIGURATION Size Bank 0 Bank 1 Bank 2 1MB (1) 256K x 36 None None 2MB None (4) 256K x 9 (4) 256K x 9 2MB (1) 512K x 36 None None 4MB None (4) 1M x 9 None 4MB (1) 1M x 36 None None 5MB None (4) 1M x 9 (4) 256K x 9 6MB (1) 512K x 36 (4) 1M x 9 None 8MB (1) 1M x 36 (4) 1M x 9 None 8MB (1) 2M x 36 None None 8MB None (4) 1M x 9 (4) 1M x 9 10MB (1) 512K x 36 (4) 1M x 9 (4) 1M x 9 12MB (1) 1M x 36 (4) 1M x 9 (4) 1M x 9 12MB (1) 2M x 36 (4) 1M x 9 None 16MB (1) 2M x 36 (4) 1M x 9 (4) 1M x 9 16MB None (4) 4M x 9 None DRAM CONFIGURATION (CON’T) Size Bank 0 Bank 1 Bank 2 17MB None (4) 4M x 9 (4) 256K x 9 18MB (1) 512K x 36 (4) 4M x 9 None 20MB (1) 1M x 36 (4) 4M x 9 None 20MB None (4) 4M x 9 (4) 1M x 9 22MB (1) 512K x 36 (4) 4M x 9 (4) 1M x 9 24MB (1) 1M x 36 (4) 4M x 9 (4) 1M x 9 24MB (1) 2M x 36 (4) 4M x 9 None 28MB (1) 2M x 36 (4) 4M x 9 (4) 1M x 9 32MB None (4) 4M x 9 (4) 4M x 9 34MB (1) 512K x 36 (4) 4M x 9 (4) 4M x 9 36MB (1) 1M x 36 (4) 4M x 9 (4) 4M x 9 40MB (1) 2M x 36 (4) 4M x 9 (4) 4M x 9 CACHE CONFIGURATION Size Bank 0 Bank 1 TAG U1 64KB (4) 8K x 8 (4) 8K x 8 (1) 8K x 8 (1) 64K x 1 128KB (4) 32K x 8 None (1) 8K/32K x 8 (1) 64K x 1 256KB (4) 32K x 8 (4) 32K x 8 (1) 32K x 8 (1) 64K x 1 CACHE JUMPER CONFIGURATION Size J16 None Pins 1 & 2, 3 & 4, 5 & 6, 9 & 10 closed 64KB Open 128KB Pins 1 & 2, 5 & 6, 7 & 8 closed 256KB Pins 1 & 2, 3 & 4, 5 & 6, 9 & 10 closed VIDEO MEMORY CONFIGURATION Size Bank 0 Bank 1 512KB 512KB None 1MB 512KB 512KB Note: The size of the video memory chips are unidentified. CPU SPEED SELECTION Speed J26 J27 25MHz Pins 1 & 2 closed Pins 2 & 3 closed 33MHz Pins 1 & 2 closed Pins 1 & 2 closed 50iMHz Pins 1 & 2 closed Pins 2 & 3 closed 66iMHz Pins 1 & 2 closed Pins 1 & 2 closed CPU TYPE SELECTION Type J19 80486SX Pins 1 & 3, 2 & 4 closed ODP486SX Pins 1 & 3, 2 & 4 closed 80487SX Pins 1 & 3, 2 & 4 closed 80486DX Pins 3 & 5, 4 & 6 closed ODP486DX Pins 3 & 5, 4 & 6 closed 80486DX2 Pins 3 & 5, 4 & 6 closed