OPTi 82C283 (Block Interleave SX/AT)
Chipset parts: OPTi 82C283 (any brand) 82C206


It's implemented with the 82C283 and a standard peripheral controller like OPTi/C&T 82C206 or the VLSI 82C100.

Documented parts

82C283 386SX System Controller

The 82C283 is a highly integrated, AT system logic VLSI chip for high-end 386SX/AT systems. It integrates a local memory controller (local memory is on-board memory), AT bus controller, and data bus controller into one chip. It is designed for systems running at 16MHz, 20MHz, 25MHz, and 33MHz*. A high performance, compact 386SX/AT system is readily implemented with the 82C283 and a standard peripheral controller like OPTi's 82C206 or the 82C100 (with Dallas Semi-conductor (DS1287).

*Rev B Only


  • 82C283A 16-25MHz
  • 82C283B 16-33MHz


  • Flexible DRAM banks configuration
    • Supports 256K, 1M and 4M DRAM modules (16MB total)
  • Block interleave mode operations
    • Block interleaving at a block size of 512 bytes
  • BIOS shadow RAM
    • Shadow RAM for system, video and adapter BIOS
  • Memory remapping
  • Flexible multiplexed DRAM address
  • Programmable AT bus clock
  • Turbo switch
  • 160-pin PQFP (Plastic Quad Flat Pack)

The 82C206 Integrated Peripheral Controller (IPC) is a single-chip integration of all the main peripheral parts attached to the X bus of PC/AT architecture. The 82C206 replaces the following peripheral logic on motherboards:

  • two 8237 DMA controllers
  • two 8259A interrupt controllers
  • one 8254 timer/counter
  • one 146818A-compatible real-time clock
  • one 74LS612 memory mapper


  • Seven DMA channels
  • 13 interrupt request channels
  • two timer/counter channels

Four DMA transfer modes supported:

  • Single
  • Block
  • Demand
  • Cascade

Special Commands provided for ease of programming:

  • Clear byte pointer flip-flop
  • Set byte pointer flip-flop
  • Master clear
  • Clear request mask register
  • Clear mode register counter

Other features:

  • Contains 114 bytes of CMOS RAM
  • 8MHz DMA clock with programmable internal divider for 4MHz operation
  • 16MB DMA address space
  • Programmable wait states for DMA cycles
  • Reduced recovery time (120ns) between I/O operations for the 8237, 8259A and 8254
  • 84-pin PLCC (plastic leadless chip carrier) or 100-pin QFP (quad flat pack)
Drivers: not available
Documentation: 3 files


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