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**82395SX     Smart Cache                                     12/17/90
***Notes:...
**82396SX     Smart Cache                                     12/17/90...
**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...
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*VIA...
**VT82C597/AT  Apollo VP3, Single-Chip for Pentium with AGP  <10/03/97
***Info:...
***Configurations:...
***Features:
o   PCI/ISA Green PC Ready
    - Supports separately powered 3.3V (5V tolerant) interfaces to 
      system memory, AGP, and PCI bus
    - Supports 3.3V and sub-3.3V interface to CPU
    - PC-97 compatible using VT82C586B South Bridge with ACPI Power 
      Management
o   High Integration
    - Single chip implementation for 64-bit Socket-7-CPU, 64-bit 
      system memory, 32-bit PCI and 32-bit AGP interfaces
    - Apollo VP3  Chipset: VT82C597 or VT82C597AT  system controller 
      and VT82C586B  PCI to ISA bridge
    - Chipset includes UltraDMA-33 EIDE, USB, and Keyboard / PS2-Mouse 
      Interfaces plus RTC / CMOS on chip
o   Flexible CPU Interface
    - Supports 64-bit Pentium, AMD 5k86, AMD 6k86 and Cyrix 6x86 CPUs
    - CPU external bus speed up to 66 MHz (internal 233MHz and above)
    - Supports CPU internal write-back cache
    - System management interrupt, memory remap and STPCLK mechanism
    - Cyrix 6x86 linear burst support
    - CPU NA# / Address pipeline capability
    - 4 cache lines of CPU/cache-to-DRAM post-write buffers
    - 4 quadwords of CPU/cache-to-DRAM read-prefetch buffers
o   Advanced Cache Controller
    - Direct map write back or write through secondary cache
    - Pipelined burst synchronous SRAM (PBSRAM) cache support (with 
      global write enable feature)
    - Flexible cache size: 0K / 256K / 512K / 1M / 2MB
    - 32 byte line size to match the primary cache
    - Integrated 10-bit tag comparator
    - 3-1-1-1 read/write timing for PBSRAM access at 66 MHz
    - 3-1-1-1-1-1-1-1 back to back read timing for PBSRAM access at 
      66 MHz
    - Sustained 3 cycle write access for PBSRAM access or CPU to DRAM 
      and PCI bus post write buffers at 66 MHz
    - Data streaming for simultaneous primary and secondary cache line 
      fill
    - System and video BIOS cacheable and write-protect
    - Programmable cacheable region and cache timing
o   AGP Controller
    - AGP v1.0 compliant
    - Supports SideBand Addressing (SBA) mode (non-multiplexed 
      address/data)
    - Supports 133MHz 2X mode for AD and SBA signalling
    - Pipelined split-transaction long-burst transfers up to 533 MB/
      sec
    - Eight level read request queue
    - Four level posted-write request queue
    - Thirty-two level (quadwords) read data FIFO (128 bytes)
    - Sixteen level (quadwords) write data FIFO (64 bytes)
    - Intelligent request reordering for maximum AGP bus utilization
    - Supports Flush/Fence commands
o   GART
    - One level TLB structure
    - Sixteen entry fully associative page table
    - LRU replacement scheme
    - Independent GART lookup control for host / AGP / PCI master 
      accesses
o   Intelligent PCI Bus Controller
    - PCI buses are synchronous to host CPU bus
    - 33 MHz operation on the primary PCI bus
    - 66 MHz PCI operation on the AGP bus
    - PCI-to-PCI bridge configuration on the 66MHz PCI bus
    - Separate data buffers for the two PCI buses
    - Peer concurrency
    - Concurrent multiple PCI master transactions;  i.e., allow PCI 
      masters from both PCI buses active at the same time
    - Allows PCI master access while ISA master/DMA is active
    - PCI master snoop ahead and snoop filtering
    - Five levels (double-words) of CPU to PCI posted write buffers
    - Byte merging in the write buffers to reduce the number of PCI 
      cycles and to create further PCI bursting possibilities
    - Zero wait state PCI master and slave burst transfer rate
    - PCI to system memory data streaming up to 132Mbyte/sec
    - Enhanced PCI command optimization (MRL, MRM, MWI, etc.)
    - Forty-eight levels (double-words) of post write buffers from PCI 
      masters to DRAM
    - Sixteen levels (double-words) of prefetch buffers from DRAM for 
      access by PCI masters
    - Supports L1/L2 write-back forward to PCI master read to minimize 
      PCI read latency
    - Supports L1/L2 write-back merged with PCI master post-write to 
      minimize DRAM utilization
    - Transaction timer for fair arbitration between PCI masters 
      (granularity of two PCI clocks)
    - Symmetric arbitration between Host/PCI bus for optimized system 
      performance
    - Complete steerable PCI interrupts
    - PCI-2.1 compliant, 32 bit 3.3V PCI interface with 5V tolerant 
      inputs
o   Advanced High-Performance DRAM Controller
    - 66MHz DRAM interface
    - Concurrent CPU and AGP access
    - FP, EDO, SDRAM, and SDRAM-II
    - 66MHz DDR (Double Data Rate) supported for SDRAM-II
      (supports central and edge DQ, bidirectional DS, and optional 
      SDR write)
    - Different DRAM types may be used in mixed combinations
    - Different DRAM timing for each bank
    - Mixed 1M / 2M / 4M / 8M / 16MxN DRAMs
    - 6 banks up to 1GB DRAMs
    - Flexible row and column addresses
    - 64-bit data width only
    - 3.3V DRAM interface with 5V-tolerant inputs
    - Optional bank-by-bank ECC (single-bit error correction and 
      multi-bit error detection) or EC (error checking only) for DRAM 
      integrity
    - Two-bank interleaving for 16Mbit SDRAM support
    - Two-bank and four bank interleaving for 64Mbit SDRAM support 
      (14 MA lines)
    - Supports maximum 8-bank interleave (i.e., 8 pages open 
      simultaneously);  banks are allocated based on LRU
    - Seamless DRAM command scheduling for maximum DRAM bus utilization
      (e.g., precharge other banks while accessing the current bank)
    - Four cache lines (16 quadwords) of CPU/cache to DRAM write 
      buffers
    - Concurrent DRAM writeback
    - Read around write capability for non-stalled CPU read
    - Burst read and write operation
    - 5-2-2-2 on page, 8-2-2-2 start page and 11-2-2-2 off page timing 
      for EDO DRAMs at 66 MHz
    - 6-1-1-1 on page, 8-1-1-1 start page and 10-1-1-1 off page for 
      SDRAMs at 66 MHz
    - 5-2-2-2-3-2-2-2 back-to-back accesses for EDO DRAM at 66 MHz
    - 6-1-1-1-3-1-1-1 back-to-back accesses for SDRAM at 66 MHz
    - BIOS shadow at 16KB increment
    - Decoupled and burst DRAM refresh with staggered RAS timing
    - Programmable refresh rate, CAS-before-RAS refresh and refresh on 
      populated banks only
o   Built-in NAND-tree pin scan test capability
o   3.3V, 0.5um, high speed / low power CMOS process
o   472 pin BGA Package
o   Alternate pinouts available to optimally accommodate different PCB 
    form factors
    - VT82C597 for ATX and NLX
    - VT82C597AT for Baby AT and ATX

**VT82C598MVP  Apollo MVP3,Single-Chip 66/75/83/100MHz & AGP <09/22/97...
**VT8501       Apollo MVP4,Single-Chip 66-100MHz & AGP       <11/04/98...
**VT82C680     Apollo P6, Pentium-Pro Chip Set               <08/30/96...
**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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