Epson 486SX - Manual (Page 199)

Appendix D
Specifications
CPU and Memory
32-bit CPU
System speed
System memory
ROM
Shadow RAM
Math coprocessor
Clock/calendar
Cache controller
25 MHz system: 80486SX processor,
50 MHz system: 80486DX2/50 processor
25 MHz regardless of CPU; for 80486DX2/50,
50 MHz speed is internal only; 8 MHz
speed is simulated by inserting wait states;
high/low speed selection through
software or keyboard command; 0 wait
state memory access at high speed
4MB RAM standard soldered onto the
memory card; base memory of either
256KB, 512KB, or 640KB, selectable
through jumpers; memory expandable
using 256KB or 1MB SIMMs up to 16MB
(maximum); SIMMs must be 80ns (or
faster) access speed
128KB (includes system and VGA BIOS)
0 wait state access speed; automatically
copies both ROM BIOS and video ROM
into RAM
Standard for 50 MHz model; on 25 MHz
model, 80486SX microprocessor can be
replaced with optional 80487SX chip
Real-time clock, calendar, and 50-byte
CMOS RAM; battery backup
82385 (25 MHz) standard
Specifications D-1