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**82485       Turbo Cache (and 485Turbocache)                      c90
***Notes:...
***Info:
The 82485 is  a second-level cache controller designed  to improve the
performance  of  Intel486  Microprocessor  systems.  One  82485  cache
controller supports  64K or  128K bytes of  second level  cache memory
that maps  to the  entire 4 Gigabytes  of the  Intel486 microprocessor
address space. The controller  is completely software transparent. One
controller plus SRAMs  provides a 64K or a  128K cache. External EPROM
can  be  cached  yet  remain  write protected.   The  82485  is  fully
compatible  with the  Intel486  microprocessor. All  Intel486 CPU  bus
cycles and timings are supported.

A complete, optional second level  cache controller using the 82485 is
available  as the 485Turbocache  Module from  Intel (data  sheet order
number 240722).

2.0 FUNCTIONAL DESCRIPTION
2.1 Introduction
The 82485 is a single ported, two-way set associative cache controller
designed specifically  to interface with  the Intel486 microprocessor.
The controller supports either a sectored configuration (two lines per
tag) or  a non-sectored configuration  (one line per tag).   The 82485
will directly support a nonsectored  64K data cache or a 128K sectored
data cache.  Both the 64K and  128K configurations are able to map the
entire 4 gigabytes of  the Intel486 microprocessor address space.  The
82485 interfaces directly to  the Intel486 microprocessor.  All Intel-
486 CPU bus cycles and timings are supported.  The 82485 also supports
0 wait  state processor operation  when there is  a cache hit  and has
provisions to support invalidation cycles, BOFF# cycles, and premature
BLAST# terminations.  The controller  is look aside (monitors bus act-
ivity in parallel to the processor) and write through (all writes pro-
pagate to the  system bus), so it supports  the same cache consistency
mechanisms as the  Intel486 CPU.  The controller also  provides a safe
method to cache ROM BIOS through the  use of a write protect pin and a
write protect strapping option.

The data cache  (Static RAM) resides external to  the 82485. The 82485
provides all  controls for  the SRAMs.  No  external latches  or tran-
ceivers are  required.  The 82485  output buffers support up  to eight
SRAMs.  A  64K cache can be  designed with only  five components; nine
components for a 128K cache.  Two-way set associativity is provided by
dual banked SRAMs. Data parity is supported.

The  82485  can  be  used  to  design  a  custom  second  level  cache
configuration. For an easier system design and higher integration, the
82485M Turbocache  can be used  (see data sheet order  number 240722).
This  module is  a  complete second  level  cache in  one package.  It
consists  of a single  82485 cache  controller and  SRAM to  provide a
complete 64K or 128K second level Intel486 microprocessor second level
cache.

***Versions:...
***Features:...
**82489DX       Advanced Programmable Interrupt Controller    10/12/92...
**82495DX/490DX DX CPU-Cache Chip Set                           <Sep91...
**82495XP/490XP Cache Controller / Cache RAM (for i860)       06/05/91...
**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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*SIS...
**5595       Pentium PCI System I/O                          <12/24/97
***Notes:...
***Info:...
***Versions:...
***Features:...
**950        LPC I/O                                         <07/16/99...
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*VIA...
**VT82C680     Apollo P6, Pentium-Pro Chip Set               <08/30/96
***Notes:...
***Info:
The  VT82C680  Apollo-P6 is  a  high  performance, cost-effective  and
energy efficient  chip set for  the implementation of  PCI/ISA desktop
and  notebook personal  computer systems  based  on the  64 bit  Intel
Pentium-Pro  super-scalar  processors.   The chipset  supports  multi-
Pentium-Pro configuration  with Intel GTL+ driver  and receiver inter-
face up  to 66 MHz external  CPU bus speed.  The  chipset supports the
Pentium-Pro CPU multi-phase bus protocols for split transactions, four
level deep  in-order queue and  deferred transactions for  optimal CPU
throughput.

The VT82C680 chip set consists  of the VT82C685 system controller, the
VT82C687 data buffer and the  VT82C586 PCI to ISA bridge. The VT82C680
supports six banks  of DRAMs up to 1 GB.  The DRAM controller supports
Standard Page Mode DRAM, EDO-DRAM, Burst EDO-DRAM and Synchronous DRAM
in a  flexible mixed/match manner. The Burst-EDO  and Synchronous DRAM
allows zero wait state bursting between the DRAM and the VT82C687 data
buffers at  66 MHz. The six  banks of DRAM allow  arbitrary mixture of
1M/2M/4M/8M/16MxN  DRAMs  with optional  bank-by-bank  ECC and  parity
support. The chipset supports sixteen level (quadwords) of CPU to DRAM
write  buffers and  sixteen  level  (quadwords) of  DRAM  to CPU  read
buffers to  maximize the CPU bus  and DRAM utilization.  The peak data
transfer rate for the EDO and Synchronous DRAM (or Burst EDO) DRAMs is
266 MB/s and 532 MB/s, respectively.

The VT82C680 supports 3.3/5v 32 bit PCI bus with 64 bit to 32 bit data
conversion.  Sixteen levels  (doublewords) of  post write  buffers are
included to  allow for concurrent  CPU and PCI  operation. Consecutive
CPU addresses  are converted into  burst PCI cycles with  Byte merging
capability  for  optimal  CPU   to  PCI  throughput.  For  PCI  master
operation,  sixteen levels  (doublewords)  of post  write buffers  and
thirty-two levels  (doublewords) of prefetch buffers  are included for
concurrent PCI bus and  DRAM/cache accesses. The chipset also supports
enhanced    PCI    bus     commands    such    as    Memory-Read-Line,
Memory-Read-Multiple  and  Memory-Write-Invalid  commands to  minimize
snoop overhead.  In addition,  the chipset supports  advanced features
such as  snoop ahead, snoop  filtering, CPU write-back forward  to PCI
master  and CPU  write-back  merged  with PCI  post  write buffers  to
minimize PCI  master read latency  and DRAM utilization.  The VT82C586
PCI to ISA bridge supports  four levels (doublewords) of line buffers,
type F DMA transfers and  delay transaction to allow efficient PCI bus
utilization (PCI-2.1 compliant). The VT82C586 also includes integrated
keyboard controller  with PS2 mouse support,  integrated DS12885 style
real time  clock with  extended 128 Byte  CMOS RAM,  integrated master
mode enhanced  IDE controller with full scatter  and gather capability
and extension  to 33 MB/sec UltraDMA-33 transfer  rate, integrated USB
interface with root hub and  two function ports with built-in physical
layer transceiver, and OnNow/ACPI compliant advanced configuration and
power management  interface. A complete main board  can be implemented
with only six TTLs.

The VT82C680 is ideal for  high performance, high quality, high energy
efficient and  high integration desktop and  notebook PCI/ISA computer
systems.

***Configurations:...
***Features:...
**Support chips:
**VT82C505     Pentium/486 VL to PCI Bridge                  <05/30/94...
**VT82C586/A/B PCI Integrated Peripheral Controller          <10/13/96...
**VT82C596/A   Mobile PCI Integrated Peripheral Controller   <11/05/97...
**VT82C686A/B  PCI Super-I/O Integrated Peripheral Ctrl.     <02/10/98...
**Later P-Pro/II/III/Celeron...
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