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**82C721   Universal Peripheral Controller III                 c:May93
***Info:
The CHIPS  82C721 enhanced I/O peripheral controller  is a single-chip
solution  offering  complete  I/O  capabilities for  PC/AT  and  PC/XT
environments.  The  82C721   supports  motherboard  applications  with
configuration via software.

The  82C721  features  a   floppy  disk  controller,  a  digital  data
separator, two 16450 compatible UARTs, a bi-directional parallel port,
an IDE interface control logic and a game port chip select.

The floppy  disk controller is software compatible  with NEC uPD72065B
floppy  disk controller.  The  controller supports  up to  four drives
directly. The digital data separator is capable of data transfer rates
up to 500kb/sec and requires no external components.

The 82C721 has two UARTs  which are compatible with NS16450 UARTs. The
IDE control logic provides a  complete IDE interface for embedded hard
disk  drives.  The  bidirectional  parallel  port  maintains  complete
compatibility with ISA and PS/2  parallel ports.  It can be configured
for either output mode or for bidirectional mode.

The  configuration   RAM  and  circuitry   support  programmable  base
addresses for  all the registers. Selection of  sources of interrupts,
enabling and configuring of on-chip  subsystems and the control of the
configuration  process itself  are also  handled by  this RAM  and its
associated circuitry.  The game port chip select provides a predefined
I/O address decode for games and joy stick applications.

The 82C721,  designed for  motherboard applications, is  provided with
several  power  management features,  which  are controllable  through
hardware  or  software. In  hardware,  the  device  can be  completely
powered down through  a power-down pin.  In this  mode, all inputs are
disabled, all outputs are inactive,  and the contents of all registers
are  preserved  (as long  as  the  power  supply is  maintained).   In
software,   the  device   allows  each   port  to   be   powered  down
independently.

The  82C721 features 24mA  drivers for  output buffers,  including the
host  data bus  and  the parallel  port  data bus.  The floppy  output
drivers  are  capable  of  sinking  48mA. The  host  interface  is  PC
compatible and can be connected directly to the ISA bus.

***Versions:...
***Features:...
**82C735   I/O Peripheral Controller With Printgine            c:Jul93...
**82C835   Single CHIP 386sx AT Cache Controller               c:Apr91...
**F87000   Multi-Mode Peripheral Chip                         11/23/93...
**Other:...
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*Contaq  . . . . . [no datasheets, some info]...
*Efar Microsystems [no datasheets, some info]...
*ETEQ...
*Faraday...
*Forex . . . . . . [List only, no datasheets found]...
*Intel...
**82495XP/490XP Cache Controller / Cache RAM (for i860)       06/05/91
***Notes:...
***Info:...
***Features:
o   Two-Way, Set Associative, Secondary Cache for i860 XP 
    Microprocessor
o   50 MHz "No Glue" Interface with CPU
o   Configurable
    - Cache Size 256 or 512 Kbytes
    - Line Width 32, 64 or 128 Bytes
    - Memory Bus Width 64 or 128 Bits
o   Dual-Ported Structure Permits Simultaneous Operations on CPU and
    Memory Buses
o   Efficient MRU Way Prediction
    - Zero Wait States on MRU Hit
    - One Walt State on MRU Miss
o   Dynamically Selectable Update Policies
    - Write-Through
    - Write-Once
    - Write-Back
o   MESI Cache Consistency Protocol
o   Hardware Cache Snooping
o   Maintains Consistency with Primary Cache via Inclusion Principle
o   Flexible User-Implemented Memory Interface Enables Wide Range of
    Product Differentiation
    - Clocked or Strobed
    - Synchronous or Asynchronous
    - Plpelining
    - Memory Bus Protocol
o   82495XP Cache Controller Available in 208-Lead Ceramic Pin Grid 
    Array Package
o   82490XP Cache RAM Available in 84-Lead Plastic Quad Flatpack 
    Package

**82496/491     Cache Controller / Cache RAM (for P5 Pentium) 03/22/93...
**82497/492   Cache Controller / Cache RAM (for P54 Pentium)    <Nov94...
**82498/493   Cache Controller / Cache RAM (for P54 Pentium)    <Nov94...
**
**Later chipsets (basic spec):
**440 series:...
**450NX  (?)            06/29/98:...
**?????  (Profusion)    c:99...
**800 series...
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**Early Chipsets:
PCCHIP1           286/386SX Found on: M205/M209
PCCHIP2           386DX     Found on: M321
CHIP3             386DX     Seen on: a 386DX motherboard  c92
CHIP5 (4L04F1282) 386DX     Seen on: a 486DLC motherboard c92
CHIP6 (4L04F1666) [partnered with CHIP5]
CHIP11, CHIP13    486       Seen on: an isa/vlb motherboard c93

**Later Chipsets:...
*SIS...
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*TI (Texas Instruments)...
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