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**82430MX     PCIset (Pentium) MX (Mobile Triton)(82437/438MX)11/01/95
***Notes:...
***Info:
The  Intel 430MX  PCIset  consists of  the  82437MX System  Controller
(MTSC). two  82438MX Data  Paths (MTDP), and  the 82371MX PCI  I/O IDE
Xcelerator (MPIIX). The PCIset forms a Host-to-PCI bridge and provides
the second level cache control and a full function 64-bit data path to
main  memory. The  MTSC  integrates  the cache  and  main memory  DRAM
control functions  and provides bus control for  transfers between the
CPU, cache, main memory, and the  PCI Bus. The second level (L2) cache
controller supports a  write-back cache policy for cache  sizes of 256
Kbytes and 512 Kbytes. Cacheless designs are also supported. The cache
memory can  be implemented with  either standard, burst,  or pipelined
burst SRAMs.  An external Tag RAM is  used for the address  tag and an
internal Tag  RAM for the  cache line status  bits. For the  MTSC DRAM
controller,  four rows  are supported  for up  to 128  Mbytes  of main
memory. The MTSC optimized PCI interface allows the CPU to sustain the
highest  possible  bandwidth  to  the  graphics frame  buffer  at  all
frequencies.  Using  the snoop  ahead  feature,  the  MTSC allows  PCI
masters to  achieve full  PCI bandwidth.  The  MTDPs provide  the data
paths  between the  CPU/cache,  main memory,  and  PCI. For  increased
system performance.  the MTDPs contain read prefetch  and posted write
buffers.

***Configurations:...
***Features:...
**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...
**82485       Turbo Cache (and 485Turbocache)                      c90...
**82489DX       Advanced Programmable Interrupt Controller    10/12/92...
**82495DX/490DX DX CPU-Cache Chip Set                           <Sep91
***Notes:...
***Info:
The 50 MHz Intel486 DX  CPU-Cache Chip Set provides a high performance
solution  for  servers  and  high-end desktop  systems.   This  binary
compatible solution  has been optimized  to provide 50 MHz,  zero wait
state performance. The CPU-Cache chip set combines the 50 MHz Intel486
Microprocessor with  the 82495DX/82490DX cache  subsystem. It delivers
integer  performance of  41 V1.1  Dhrystone  MlPs and  a SPEC  integer
rating  of  27.9.  The  cache  subsystem  features  the 82495DX  Cache
Controller and the 82490DX Dual  Ported Data RAM.  Dual ported buffers
and registers  of the  82490DX allow the  82495DX Cache  Controller to
concurrently handle CPU bus, memory bus, and internal cache operations
for maximum performance.

The CPU-Cache Chip Set offers  many features that are ideal for multi-
processor  based systems.  The  Write-Back feature  provides efficient
memory  bus utilization  by reducing  bus traffic  through eliminating
unnecessary  writes  to main  memory.   The  CPU-Cache  chip set  also
supports MESI protocol and monitors  the memory bus to guarantee cache
coherency.

The 50  MHz Intel486  DX CPU and  82495DX/82490DX Cache  subsystem are
produced on  Intel's latest CHMOS  V process which  features submicron
technology and triple layer metal.

3.0 ARCHITECTURAL OVERVIEW
3.1 Introduction
The Intel486 CPU-cache chip  set provides a tightly coupled processing
engine  based on  the Intel486  microprocessor and  a  cache subsystem
comprised of  the 82495DX cache controller and  multiple 82490DX cache
components.   Figure 3.1  [see datasheet]  diagrams the  basic config-
uration.

The cache subsystem provides a  gateway between the CPU and the memory
bus. All CPU accesses that  can be serviced locally are transparent to
the memory bus and serve to avoid bus traffic.  As a result, the cache
chip  set  reduces memory  bus  bandwidth  to  both increase  Intel486
processor  performance and  support efficient  multiprocessor systems.
The  cache subsystem also  decouples the  CPU from  the memory  bus to
provide  zero-wait-state  operation at  high  clock frequencies  while
allowing relatively slow and inexpensive memories.

The  CPU-cache chip  set  prevents latency  and bandwidth  bottlenecks
across  a variety  of  uniprocessor and  multiprocessor designs.   The
processor’s  on-chip cache  supports  a  very wide  CPU  data bus  and
high-speed data  movement. The second-level cache  greatly extends the
capabilities of the on-chip cache resources, enabling a larger portion
of memory cycles to be satisfied independently of the memory bus.

3.2 CPU-Cache Chip Set Description
The chip set is comprised of three functional blocks: 

3.2.1 CPU
The chip  set includes a  special version of the  Intel486DX micropro-
cessor at  50 MHz.  The Intel486DX Microprocessor  Data Sheet provides
complete component specifications.

3.2.2 CACHE CONTROLLER
The 82495DX cache controller is  the main control element for the chip
set. providing  tags and line  states. and determining cache  hits and
misses. The 82495DX executes all  CPU bus requests and coordinates all
main memory accesses with the memory bus controller (MBC).

The 82495DX  controls the data  paths of the 82490DX  cache components
for cache hits and misses and furnishes the CPU with needed data.  The
controller  dynamically adds  wait  states as  needed  using the  most
recently used (MRU) prediction algorithm.

The 82495DX also performs memory bus snoop operations in shared memory
systems  and drives  the  cycle address  and  other attributes  during
memory bus accesses. Figure  3.2 [see datasheet] diagrams the 82495DX.

3.2.3 CACHE SRAM

Multiple  82490DX cache  components provide  the cache  SRAM  and data
path. Each component  includes the latches, muxes and  logic needed to
work in lock  step with the 82495DX to efficiently  serve both hit and
miss  accesses.  The 82490DX  components take  full advantage  of VLSI
silicon   flexibility   to  exceed   the   capabilities  of   discrete
implementations.  The  82490DX components support  zero-wait-state hit
accesses  and  concurrent  CPU  and  memory  bus  accesses,  and  they
replicate MRU  bits for autonomous  way prediction. During  memory bus
cycles. the 82490DX components act as a gateway between CPU and memory
buses. Figure 3.3 [see datasheet] diagrams an 82490DX cache component.

3.3 Secondary Cache Features

The 82495DX  cache controller and  82490DX cache components  provide a
unified, software  transparent secondary  data and  instruction cache.
The cache enables  a highspeed processor core  that provides efficient
performance even when paired with a significantly slower memory bus.

The secondary  cache interprets  CPU bus cycles  and can  service most
memory read and  write cycles without accessing main  memory.  I/O and
other special cycles are passed directly to the memory bus.  The cache
has a dual-port  structure that permits concurrent CPU  and memory bus
operation.

The 82495DX  cache controller  contains the 8K  tag entries  and logic
needed to support a cache as  large as 256K. Combinations of between 4
and 9 82490DX cache SRAMs are  used to create caches ranging from 128K
to 256K, with or without data parity.

The  MBC provides  logic  needed  to interface  the  CPU, 82495DX  and
82490DX  to the  memory  bus.   Because the  MBC  also affects  system
performance.  its design can be the basis of product differentiation.

***Configurations:...
***Features:...
**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...
**HT18          80386SX Single Chip                            c:Sep91
***Info:...
***Configurations:...
***Features:...
**HT21          386SX/286 Single Chip (20 MHz)                 c:Aug91...
**HT22          386SX/286 Single Chip (25 MHz)                 c:Sep91...
**HT25          3-volt Core Logic for 386SX                    c:Dec92...
**HT35          Single-Chip Peripheral Controller [partial info]     ?...
**HTK320        386DX Chip Set                                 c:Sep91...
**HTK340        "Shasta" 486 Chip Set                          c:Jun92...
**Support Chips:
**HT44          Secondary Cache                                c:Jun92...
**Other:...
*HMC (Hulon Microelectronics)...
*Logicstar...
*Motorola...
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*SIS...
*Symphony...
*TI (Texas Instruments)...
*UMC...
*Unresearched:...
*VIA...
*VLSI...
*Western Digital...
*Winbond...
*ZyMOS...
*General Sources:...

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