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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...
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*SIS...
**950 LPC I/O <07/16/99
***Info:
The SIS950 is a LPC Interface based highly integrated Super I/O. The
SIS950 provides the most commonly used legacy Super I/O functionality
plus the latest Environment Control initiatives, such as Hardware
Monitor, Fan Speed Controller and SiS’s "SmartGuardian" function. The
device’s LPC interface complies with Intel "LPC Interface
Specification Rev. 1.0" (Sept. 29, 1997). The SIS950 meets the
"Microsoft PC98 & PC99 System Design Guide" requirements and is ACPI
compliant.
The SIS950 features the enhanced hardware monitor providing 3 thermal
inputs from remote thermistors, thermal diode or diode-connected
transistor (2N3904). The device also provides the SiS innovative
intelligent automatic Fan ON/OFF & speed control functions
(SmartGuardian) to reduce overall system noise and power consumption.
The SIS950 has integrated nine logical devices, featuring an
Environment Controller (controls three Fans). The Environment
Controller has temperature, voltage and Fan Speed monitors. One Fan
Speed Controller is responsible to control three fan speeds through
three 128 steps of Pulse Width Modulation (PWM) output pins and to
monitor three fan's tachometer inputs.
Other features include one high-performance 2.88MB floppy disk
controller, with digital data separator, supporting two 360K/ 720K/
1.2M/ 1.44M/ 2.88M floppy disk drives. One multi-mode high-performance
parallel port features the bi-directional Standard Parallel Port
(SPP), the Enhanced Parallel Port (EPP V. 1.7 and EPP V. 1.9 are
supported), and the IEEE 1284 compliant Extended Capabilities Port
(ECP). Two 16C550 standard compatible enhanced UARTs perform
asynchronous communication, and support IR, one consumer remote
control (TV remote) IR, one MPU-401 UART mode compatible MIDI port,
one game port with built-in 558 quad timers and buffer chips to
support direct connection of 2 joysticks, and six ports (48 GPIO
pins). There is also a flash ROM interface with Address (FA[0:18]),
Data (FD[0:7]), and supporting three control signals FCS#, FWE# and
FRD#. In addition, a SmartGuardian engine is provided to monitor the
system condition and reacts to the detected condition accordingly.
These nine logical devices can be individually enabled or disabled via
software configuration registers. The SIS950 utilizes power-efficient
circuitry to reduce power consumption. Once a logical device is
disabled, the inputs are gated inhibit, the outputs are TRI-STATE and
the input clock is disabled. The SIS950 requires a single 48/24 MHz
clock input and operates with a single +5V power supply.
The SIS950 is available in 128-pin PQFP (Plastic Quad Flat Package).
***Versions:...
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