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**82340DX     Chip Set (VLSI) (82346/82345/82355)             01/08/90
***Notes:...
***Info:...
***Configurations:...
***Features:...
**82340SX     Chip Set (VLSI) (82343/82344)                   01/25/89...
**82350       EISA Chip Set                                   07/10/89...
**82350DT     EISA Chip Set                                   04/22/91...
**82420TX/ZX  PCIset (for 486) TX (Saturn), ZX (Saturn II)     c:Nov92...
**82420EX     PCIset (for 486) EX (Aries)   (82425EX/82426EX)   <Dec94...
**82430LX     PCIset (Pentium) LX (Mercury) (82433LX/82434LX) 03/22/93...
**82430NX     PCIset (Pentium) NX (Neptune) (82433NX/82434NX)    Mar94...
**82430FX     PCIset (Pentium) FX (Triton I) (82437FX/82438FX)01/31/95...
**82430MX     PCIset (Pentium) MX (Mobile Triton)(82437/438MX)11/01/95...
**82430HX     PCIset (Pentium) HX (Triton II) (82439HX)       02/12/96...
**82430VX     PCIset (Pentium) VX (Triton II) (82437VX/82438) 02/12/96...
**82430TX     PCIset (Pentium) TX (Triton II) (82439TX)       02/17/97...
**82450KX/GX  PCIset (Pentium Pro) KX/GX (Mars/Orion)         11/01/95...
**
**Support Chips:
**82091AA     Advanced Interface Peripheral (AIP)                  c93...
**8289        Bus Arbiter (808x)                                   c79...
**82289       Bus Arbiter for iAPX 286 Processor Family            c83...
**82258       Advanced Direct Memory Access Coprocessor(ADMA) 01/01/84...
**82335       High-Integration Interface Device For 386SX      c:Nov88...
**82360SL     I/O Subsystem                                   10/05/90...
**82370       Integrated System Peripheral (for 82376)         c:Oct88...
**82371FB/SB  PCI ISA IDE Xcelerator 82371FB/82371SB (PIIX/3) 01/31/95...
**82371MX     Mobile PCI I/O IDE Xcelerator (MPIIX)           11/01/95...
**82371AB     PCI-TO-ISA / IDE Xcelerator 82371AB (PIIX4)     02/17/97...
**82374/82375 PCI-EISA Bridge (82374EB/82375EB, 374SB/375SB)   c:Mar93...
**82378       System I/O (SIO) (82378IB and 82378ZB)           c:Mar93...
**82379AB     System I/O-APIC (SIO.A)                           <Dec94...
**82380       32-bit DMA Controller w/ Integrated Peripherals 02/01/87...
**82380FB/AB  PCIset: 82380FB Mobile PCI-to-PCI Bridge(MPCI2) 02/17/97...
**82384       Clock Generator and Reset Interface                  c86...
**82385       32-bit Cache Controller for 80386               09/29/87...
**82385SX     32-bit Cache Controller for 80386SX             01/25/89...
**82395DX     High Performance Smart Cache                    06/18/90...
**82395SX     Smart Cache                                     12/17/90...
**82396SX     Smart Cache                                     12/17/90
***Notes:...
***Info:
The 82396SX  Smart Cache (part number  82396SX) is a  low cost, single
chip,  16-bit  peripheral  for  Intel's i386  SX  Microprocessor.   By
storing frequently accessed code or  data from main memory the 82396SX
Smart Cache  enables the  i386 SX Microprocessor  to run at  near zero
wait states.  The  dual bus architecture allows another  bus master to
access the System Bus while the i386 SX Microprocessor operates out of
the 82396SX Smart Cache on the Local Bus.  The 82396SX Smart Cache has
a snooping mechanism which  maintains cache coherency with main memory
during these cycles.

The 823968X Smart Cache is completely software transparent, protecting
the integrity of system software.  The advanced architectural features
of the  82596SX Smart Cache offer  high performance with  a cache data
RAM size that  can be integrated on a single  chip, offering the board
space  and cost  savings needed  in  an i386  SX Microprocessor  based
system.

1.0 823968X SMART CACHE FUNCTIONAL OVERVIEW
1.1 Introduction

The primary function of a cache  is to provide local storage for freq-
uently  accessed  memory   locations.   The  cache  intercepts  memory
references and handles them  directly without transferring the request
to the System Bus. This results in lower traffic on the System Bus and
decreases latency on the Local Bus. This leads to improved performance
for a processor  on the Local Bus. It  also increases potential system
performance by  reducing each processor's demand for  System Bus band-
width, thus allowing more processors  or system masters in the system.
By providing fast access to frequently used code and data the cache is
able  to  reduce  the  average  memory  access time  of  the  i386  SX
Microprocessor based system.

The 82396SX Smart Cache is  a single chip cache subsystem specifically
designed for  use with the  i386 SX Microprocessor. The  82396SX Smart
Cache integrates 16KB cache, the Cache Directory and the cache control
logic onto  one chip. The  cache is unified  for code and data  and is
transparent to application software.  The 82396SX Smart Cache provides
a cache consistency mechanism which  guarantees that the cache has the
most recently  updated version of  the main memory.   Consistency sup-
port has no performance impact on the i386 SX Microprocessor.  Section
1.2 covers all the 82396SX Smart Cache features.

The  82396SX  Smart Cache  architecture  is  similar  to the  i486  SX
Microprocessor's on-chip cache. The  cache is four Way SET associative
with Pseudo LRU (Least  Recently Used) replacement algorithm. The line
size is  16B and a  full line is  retrieved from the memory  for every
cache miss. A TAG is associated with every 16B line. The 82396SX Smart
Cache  architecture allows for  cache read  hit cycles  to run  on the
Local Bus  even when the System  Bus is not  available.  82396SX Smart
Cache incorporates a new write buffer cache architecture, which allows
the i386  SX Microprocessor to continue operation  without waiting for
write cycles to actually update the main memory.

A  detailed  description of  the  cache  operation  and parameters  is
included in Chapter 2.

The 82396SX Smart Cache has  an interface to two electrically isolated
busses. The interface to the i386 SX Microprocessor bus is referred to
as the Local Bus (LB) interface.  The interface to the main memory and
other system devices is referred  to as the 82396SX Smart Cache System
Bus  (SB)   interface.   The  SB   interface  emulates  the   i386  SX
Microprocessor.   The  SB interface,  as  does  the  i386TM SX  Micro-
processor. operates in pipeline mode.

In addition, it is enhanced by  an optional burst mode for Line Fills.
The burst mode provides faster line fills by allowing consecutive read
cycles  to  be  executed at  a  rate  of  up  to  one word  per  clock
cycle. Several bus masters (or several 82396SX Smart Caches) can share
the same  System Bus and the  arbitration is done  via the SHOLD/SHLDA
mechanism (similar to the i486 SX Microprocessor).

Cache  consistency   is  maintained  by   the  SAHOLD/SEADS#  snooping
mechanism, similar  to the i486  SX Microprocessor. The  82396SX Smart
Cache  is  able to  run,  a zero  wait  state  i386 SX  Microprocessor
non-pipelined read cycle if the data exists in the cache. Memory write
cycles can run with zero wait states if the write buffer is not full.

The 82396SX Smart  Cache organization provides a higher  hit rate than
other standard configurations.  The 82396SX Smart Cache, featuring the
new high  performance write  buffer cache architecture,  provides full
concurrency  between the  electrically isolated  Local Bus  and System
Bus. This allows the 82396SX Smart Cache to service read hit cycles on
the Local Bus while running line fills or buffered write cycles on the
System Bus.

1.2 Features
1.2.1 823858X-LIKE FEATURES

o The 82396SX  Smart Cache maps  the entire physical address  range of
  the i386 SX Microprocessor (16MB)  into an 16KB cache.  Unified code
  and data cache.

o Cache attributes  are handled by  hardware.  Thus the  82396SX Smart
  Cache is  transparent to  application software.  This  preserves the
  integrity  of  system  software  and  protects  the  users  software
  investment. 

o Word  and Byte writes,  Word reads. 

o Zero wait states in read hits and in buffered write cycles. All i386
  SX  Microprocessor  cycles  are  non-pipelined (Note:  The  i386  SX
  Microprocessor must  never be pipelined  when used with  the 82396SX
  Smart Cache  - NA# must  be tied to  Vcc).

o A  hardware  cache FLUSH#  option.   The  82396SX  Smart Cache  will
  invalidate all the  Tag Valid bits in the  Cache Directory and clear
  the System Bus line buffer when FLUSH# is activated tor a minimum of
  four  CLK’s.

o The 82396SX Smart Cache supports non-cacheable accesses.

o The  82396SX  Smart  Cache  internally  decodes  the  i387  SX  Math
  Coprocessor accesses as Local  Bus cycles.

o The  System   Bus  interface  emulates  a   i386  SX  Microprocessor
  interface.  

o The 82396SX Smart Cache  supports pipelined and non-pipelined system
  interface.

o Provides  cache  consistency  (snooping):  The 82396SX  Smart  Cache
  monitors the System Bus address via SEADS# and invalidates the cache
  address if  the System Bus  address matches a  cached location.

1.2.2 NEW FEATURES

o 16KB on chip cache arranged in four banks, one bank for each way. In
  Read hit cycles,  one word is read.  In a write  hit cycle, any byte
  within the  word can be written.   In a cache fill  cycle, the whole
  line (16B) is written.  This  large line size increases the hit rate
  over smaller  line size caches.

o Cache architecture  similar to the  i486 SX Microprocessor  cache: 4
  Way  set associative  with Pseudo  LRU replacement  algorithm.  Line
  size is 16B and a full line is retrieved from memory for every cache
  miss. A  Tag Valid Bit and  a Write Protect Bit  are associated with
  every Line.

o New  write buffer  architecture  with four  word  deep write  buffer
  provides zero  wait state memory  write cycles. I/O,  Halt/ Shutdown
  and  LOCK#ed  writes  are  not  buffered.

o Concurrent Line Buffer Cacheing: The  82396SX Smart Cache has a line
  buffer that is  used as additional memory. Before  data gets written
  to the cache memory at the completion of a Line Fill it is stored in
  this buffer.  Cache  hit cycles to the line  buffer can occur before
  the line  is written to the  cache. 

o In i387 SX Math Coprocessor accesses, the 82396SX Smart Cache drives
  the READYO# in  one wait state if the READYI# was  not driven in the
  previous clock.

  Note that the timing of the 82396SX Smart Cache’s READYO# generation
  for  i387 SX  Math  Coprocessor cycles  is  incompatible with  80287
  timing.

o An enhanced System Bus interface:
  a) Burst  Option is supported in  line-fills similar to  the i486 SX
     Microprocessor.   SBRDY#  (System  Burst  READY) is  provided  in
     addition to SRDY#.  A burst is  always a 16 byte line fill (cache
     update) which is equivalent to eight word cycles.

  b) System cacheability attribute  is provided (SKEN#). SKEN# is used
     to determine whether the current  cycle is cacheable.  It is used
     to qualify Line Fill requests.

  c) SHOLD/SHLDA system  bus arbitration  mechanism is  supported.   A
     Multi  i386 SX  82396SX Smart  Cache cluster  can share  the same
     System Bus via this mechanism.

  f) Cache invalidation  cycles supported via SEAD$#. This  is used to
     provide cache coherency.

o Full Local Bus/System Bus concurrency is attained by:
  a) Servicing cache read hit cycles on the Local Bus while completing
     a Line Fill on the System  Bus. The data requested by the i386 SX
     Microprocessor is provided  over the local bus as  the first word
     of the Line Fill.

  b) Servicing cache read hit  cycles on the Local Bus while executing
     buffered write cycles on the system bus.

  c) Servicing  cache read hit cycles  on the Local  Bus while another
     bus master is running (DMA, other i386 SX Microprocessor, 82396SX
     Smart Cache, i486 SX Microprocessor, etc...)  on the System Bus.

  d) Buffering write  cycles on the Local Bus while  the system bus is
     executing other  cycles.  Write protected areas  are supported by
     the SWP# input. This enables caching of ROM space or shadowed ROM
     space.

o No Post  Input (NPI#)  provided for disabling  of write  buffers per
  cycle. This option supports memory mapped l/O designs.

o Byte  Enable Mask  (BEM)  is  provided to  mask  the processor  byte
  enables during a memory read cycle.

o A2oM# input provided for emulation of 8086 address wrap-around.

o SRAM test mode, in which the TAGRAM and the cache RAM are treated as
  standard SRAM, is provided. A Tristate Output test mode is also pro-
  vided for system debugging. In  this mode the 82396SX Smart Cache is
  isolated from  the other  devices in the  board by floating  all its
  outputs.

o Single chip, 132 lead PQFP package, 1 micron CHMOS-IV technology.

***Versions:...
***Features:...
**82485       Turbo Cache (and 485Turbocache)                      c90...
**82489DX       Advanced Programmable Interrupt Controller    10/12/92
***Notes:...
***Info:...
***Versions:...
***Features:...
**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...
*Headland/G2...
*HMC (Hulon Microelectronics)...
*Logicstar...
*Motorola...
*OPTi...
**82C700         FireStar                                         c:97
***Info:...
***Configurations:...
***Features:...
**82C701         FireStar Plus                                    c:97...
**82C750         Vendetta      [no datasheet]                        ?...
**82c801         SCWB2 DX Single Chip Solution                    c:92...
**82C802         SCWB2 PC/AT Single Chip [no datasheet]              ?...
**82C802G/GP     System/Power Management Controller (cached)      c:93...
**82C895         System/Power Management Controller (cached)   c:Sep94...
**82C898         System/Power Management Controller (non-cache)c:Nov94...
**
**Support Chips:
**82C601/2       Buffer Devices                                 <Nov94...
**82C822         PCIB (VLB-to-PCI bridge)                         c:94...
**Other:...
*PC CHIPS/Amptron/Atrend/ECS/Elpina/etc...
*SIS...
*Symphony...
*TI (Texas Instruments)...
*UMC...
*Unresearched:...
*VIA...
*VLSI...
*Western Digital...
*Winbond...
*ZyMOS...
*General Sources:...

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