Toshiba T4400SXC Maintenance Manual page 5

The T4400SXC system board shown in figure 1-3 is composed of the following major
components:
o
An 80486SX-25 CPU
o
Super Integration (SI) T9901, which stores the following components:
• Two Direct Memory Access Controller (DMAC):
• Two Programmable Interrupt Controller (PIC):
• One Programmable Interval Timer (PIT):
• One Floppy Disk Controller (FDC):
• One Serial Input/Output controller (SIO):
• One Variable Frequency Oscillator (VFO):
• One I/O Controller
o
A Real Time Clock (RTC): 146818AF
o
A KeyBoard Controller (KBC): M37452M4
o
A Power Supply Controller (PSC): 47C660
o
The following memories:
Standard RAM: 4MB
82C37
82C59
82C54
TC8565
TC8570
TC8568
Cash memory 8 KB (inside CPU)
Backup RAM: 32KB
BIOS ROM: 128 KB (96 KB are used)
This ROM contains Initial Reliability Test (IRT), Basic
Input/Output System (BIOS), and video BIOS.
Video RAM: 256KB
Optional memory cards expand memory to a maximum of 20 MB.
o
System control gate array :
o
VGA display controller:
SYS CNT-GA (344-pin)
PVGA1F: WD90C30 (132-pin)
o
The following Oscillators (OSC):
• 24 MHz OSC (Xl) is used for the FDC and VFO.
• 25.0 MHz OSC (X2) is used for the CPU.
• 14.7456 MHz OSC (X6) is used for the COM.
• 14.31818 MHz OSC (X7) is used for the KBC.
• 32.768 KHz OSC (X8) is used for the RTC.
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