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**82430FX     PCIset (Pentium) FX (Triton I) (82437FX/82438FX)01/31/95
***Notes:...
***Info:
The 82430FX  PCIset consists of  the 82437FX System  Controller (TSC),
two 82438FX Data  Paths (TDP). and the 82371FB  PCI ISA IDE Xcelerator
(PIIX). 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  TSC 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 TSC’s DRAM
controller,  five rows  are supported  for up  to 128  Mbytes  of main
memory. The  TSC's 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 TSC allows PCI masters
to achieve full PCI bandwidth. The TDPs provide the data paths between
the   CPU/cache,  main   memory,  and   PCI.   For   increased  system
performance. the TDPs contain read prefetch and posted write buffers.


1.0 ARCHITECTURE OVERVIEW OF TSC/TDP
The 82430FX PCIset (Figure 1)  [see datasheet] consists of the 82437FX
System Controller (TSC).   two 82438FX Data Path (TDP)  units, and the
82371FB PCI  IDE ISA Xcelerator (PIIX).   The TS0 and two  TDPs form a
Host-to-PCI bridge. The PIIX  is a multi-function PCI device providing
a PCI-to-ISA bridge and a  fast IDE interface.  The PIIX also provides
power management and has a plug and play port.  The two TDPs provide a
64-bit data path  to the host and to main memory  and provide a 16-bit
data path  (PLINK) between  the TSC and  TDP. PLINK provides  the data
path for CPU to PCI accesses  and for PCI to main memory accesses. The
TSC and  TDP bus  interfaces are  designed for 3V  and 5V  busses. The
TSC/TDP connect  directly to  the Pentium processor  3V host  bus; The
TSC/TDP connect  directly to 5V or  3V main memory DRAMs;  and the TSC
connects directly to the 5V PCI Bus.

DRAM Interface
The DRAM interface  is a 64-bit data path  that supports both standard
page mode and Extended Data Out  (EDO) (also known as Hyper Page Mode)
memory. The DRAM  interface supports 4 Mbytes to  128 Mbytes with five
RAS  lines available  and also  supports symmetrical  and asymmetrical
addressing for 512K, 1M, 2M, and 4M deep DRAMs.

Second Level Cache
The  TSC supports a  write-back cache  policy providing  all necessary
snoop functions and inquire cycles.   The second level cache is direct
mapped and  supports both a 256-Kbyte or  512-Kbyte SRAM configuration
using  either burst, pipelined  burst, or  standard SRAMs.   The burst
256-Kbyte configuration performance  is 3-1-1-1 for read/write cycles;
pipelined back-to-back  reads can maintain  a 3-1-1-1-1-1-1-1 transfer
rate.

TDP
Two TDPs create a 64-bit CPU and main memory data path. The TDP's also
interface  to   the  TSC's  16-bit   PLINK  inter-chip  bus   for  PCI
transactions. The combination of the 64-bit memory path and the 16-bit
PLINK bus make the TDP’s  a cost effective solution, providing optimal
CPU-to-main  memory  performance  while  maintaining a  small  package
footprint (100 pins each).

PCI interface
The  PCI interface  is 2.0  compliant  and supports  up to  4 PCI  bus
masters in addition to the PIIX bus master requests. While the TSC and
TDP's together provide the interface between PCI and main memory, only
the TSC connects to the PCI Bus.

Buffers
The TSC and TDP's together contain buffers for optimizing data flow. A
four  Qword deep  butter is  provided for  CPU-to-main  memory writes,
second  level   cache  write  back  cycles,   and  PCI-to-main  memory
transfers. This  buffer is  used to achieve  3-1-1-1 posted  writes to
main memory.   A four Dword buffer  is used for  CPU-to-PCI writes. In
addition,  a four Dword  PCI Write  Buffer is  provided which  is com-
bined with the  DRAM Write Buffer to supply a  12 Dword deep buffering
for PCI to main memory writes.

System Clocking
The processor,  second level cache,  main memory subsystem,  and PLINK
bus  all  run synchronous  to  the host  clock.   The  PCI clock  runs
synchronously at half the host clock frequency. The TSC and TDP’s have
a host clock input and the TSC has a PCI clock input. These clocks are
derived from an external source and have a maximum clock skew require-
ment with respect to each other.

***Configurations:...
***Features:...
**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...
**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...
*OPTi...
*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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