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*Intel...
**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...
*HMC (Hulon Microelectronics)...
*Logicstar...
*Motorola...
*OPTi...
*PC CHIPS/Amptron/Atrend/ECS/Elpina/etc...
*SIS...
**530/5595       (Sinbad) Host, PCI, 3D Graphics & Mem. Ctrl.<11/10/98
***Info:
The P5  A.G.P./VGA chipset, SiS530/5595, provides  a high performance/
cost index  Desktop/Mobile solution  for the Intel  Pentium P54C/P55C,
AMD K5/K6/K6-II, Cyrix M1/M2 and  other compatible Pentium CPU with 3D
A.G.P. VGA system.

The Host,  PCI, 3D A.G.P.  Video/Graphics & Memory  Controller, SiS530
integrates the  Host- to-PCI bridge,  the PCI interface, the  L2 cache
controller, the  DRAM controller, the high  performance hardware 2D/3D
VGA controller, and the PCI IDE controller.

The   Host  interface   supports   Synchronous/Asynchronous  Host/DRAM
clocking configuration to eminently improve the system performance and
DRAM compatibility issues.

The L2 cache controller can support up to 2 MB P.B. SRAM, and the DRAM
controller  can support  SDRAM  memory  up to  1.5  GBytes with  three
double-sided  SDRAM  DIMMs  configuration.  The cacheable  DRAM  sizes
support up to 256 MBytes.

The built-in fast PCI IDE controller supports the ATA PIO/DMA, and the
Ultra DMA33/66 function  that support the data transfer  rate up to 66
MB/s. It provides the separate data path for two IDE channels that can
eminently improve the performance under the multi-tasking environment.

The A.G.P. internal  interface is supported for integrated  H/W 3D VGA
controller. The  integrated VGA controller  is a high  performance and
targeted at  3D graphics application.  In addition,  the integrated 3D
Video/Graphics controller adopts the  64bits 100MHz host bus interface
high  technology  to  improve  the performance  eminently.   To  cost-
effective the PC system, the  share system memory architecture will be
adopted and  it can flexibly using  the 2MB, 4MB and  8MB frame buffer
size  from programming  the system  BIOS. [something  got  confused in
translation  there  didn't it?]  To  enhance  the system  performance,
SiS530 also supports the local  frame buffer solution and memory sizes
can support up to 8MB with SDRAM and SGRAM.

In addition  to provide  the standard interface  for CRT  monitors, it
also  provides  the Digital  Flat  Panel  Port  (DFP) for  a  standard
interface  between  a  personal  computer  and a  digital  flat  panel
monitor. This  port allows a host  computer to connect  directly to an
external  flat panel  monitor without  the need  for analog-to-digital
conversion  found  in most  flat  panel  monitors  today. As  for  DVD
solution,  the  integrated 3D  VGA  controller  also  support DVD  H/W
accelerator to improve the DVD playback performance.

The SiS5595 PCI  system I/O integrates the PCI-to-ISA  bridge with the
DDMA, PC/PCI DMA  and Serial IRQ capability, the  ACPI/Legacy PMU, the
Data  Acquisition   Interface,  the  Universal   Serial  Bus  host/hub
interface,  and the  ISA  bus  interface which  contains  the ISA  bus
controller, the DMA controllers, the interrupt controllers, the Timers
and  the  Real Time  Clock  (RTC).  It  also integrates  the  Keyboard
Controller and PS/2 mouse interface that can support keyboard power on
function  for users  to power  on system  by entering  the hot  key or
password from  keyboard. The built-in  USB controller, which  is fully
compliant to  OHCI (Open Host Controller Interface),  provides two USB
ports  capable  of  running  full/low  speed USB  devices.   The  Data
Acquisition Interface  offers the ability of  monitoring and reporting
the environmental  condition of  the PC. It  could monitor  5 positive
analog voltage inputs, 2 Fan speed inputs, and one temperature input.

In  addition, SiS5595  also supports  ACPI function  to  meet Advanced
Configuration and Power Interface (ACPI) 1.0 specification for Windows
98 environment,  it can support power-management  timer, Power button,
Real-time  clock alarm  wake up,  more  sleeping state,  ACPI LED  for
sleeping and  working state, LAN wake  up, Modem Ring In  wake up, and
OnNow initiative function.

***Configurations:...
***Features:...
**540            (Spartan) Super7 2D/3D Ultra-AGP Single C.S.<11/30/99...
**55x            SoC (System-on-chip)                        <03/14/02...
**
**Support chips:
**85C206     Integrated Peripheral Controller [no datasheet]         ?...
**5595       Pentium PCI System I/O                          <12/24/97...
**950        LPC I/O                                         <07/16/99...
**Other:...
**PII/III/Pro...
**Athlon etc...
*Symphony...
*TI (Texas Instruments)...
*UMC...
*Unresearched:...
*VIA...
*VLSI...
**VL82C380         Single chip 386DX PC/AT Controller +on-chip cache ?
***Info:...
***Configuration:...
***Features:...
**VL82C325             VL82C386SX System Cache controller            ?...
**VL82C335             VL82C386DX System Cache ctrl. [no d.sheet]    ?...
**VL82C315A/322A/3216  Kodiak 32-Bit Low-Voltage Chip Set            ?...
**VL82C420/144/146     SCAMP IV [no datasheet, some info]          c93...
**VL82C480         System/Cache/ISA bus Controller                   ?...
**VL82C481         System/Cache/ISA bus Controller                 c92...
**VL82C486         Single-Chip 486, SC486, Controller                ?...
**VL82C425         486 Cache controller                              ?...
**????????         Cheetah 486, PCI [no datasheet]                   ?...
**VL82C3216        Bus Expanding Controller Cache with write buffer  ?...
**VL82C521/522     Lynx/M                                            ?...
**VL82C530         Eagle Ð                                         c95...
**VL82C541/543     Lynx                                            c95...
**VL82C591/593     SuperCore 590                                   c94...
**VL82C594/596/597 Wildcat                                         c95...
**I/O Chips:
**VL82C106 Combination I/O chip                                      ?...
**VL82C107 SCAMP  Combination I/O chip                               ?...
**VL82C108 TOPCAT Combination I/O chip                               ?...
**VL82C110 Combination I/O chip                                      ?...
**VL82C113 SCAMP  Combination I/O chip                               ?...
**VL82C114 Combination I/O chip                                      ?...
**Video: ...
**Disk:...
**Modems:...
**Other:...
**Not sure if they actually exist...
*Western Digital...
*Winbond...
*ZyMOS...
*General Sources:...

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