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**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
***Notes:...
***Info:...
***Features:...
**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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*Winbond...
**W83877TF/TG/TD WINBOND I/O (Multi I/O) c97
***Info:
GENERAL DESCRIPTION
W83877TF/TG is an enhanced version from Winbond's most popular I/O
chip W83877F --- which integrates the disk drive adapter, serial port
(UART), IrDA 1.0 SIR, parallel port, configurable Plug-and-Play
registers for the whole chip --- plus additional powerful features:
ACPI / legacy power management, serial IRQ, and IRQ sharing.
The disk drive adapter functions of W83877TF/TG include a floppy disk
controller compatible with the industry standard 82077/765, data
separator, write pre-compensation circuit, decode logic, data rate
selection, clock generator, drive interface control logic, interrupt
and DMA logic. The wide range of functions integrated into W83877TF/TG
greatly reduces the number of components required for interfacing with
floppy disk drives. W83877TF/TG supports four 360K, 720K, 1.2M, 1.44M,
or 2.88M disk drives and data transfer rates of 250 Kb/S, 300 Kb/S,
500 Kb/S,1 Mb/S, and 2 Mb/S.
W83877TF/TG provides two high-speed serial communication ports
(UARTs), one of which supports serial Infrared communication. Each
UART includes a 16-byte send/receive FIFO, a programmable baud rate
generator, complete modem control capability, and a processor
interrupt system. One of the UARTs support infrared (IR) IrDA1.0. Both
UARTs provide legacy speed with baud rate up to 115.2K and provide
advanced speed with baud rate up to 230k, 460k, and 921k bps which
support higher speed Modems.
W83877TF/TG supports one PC-compatible printer port (SPP),
Bi-directional printer port (BPP) and also Enhanced Parallel Port
(EPP) and Extended Capabilities Port (ECP). Through the printer port
interface pins, also available are: Extension FDD Mode and Extension
2FDD Mode allowing one or two external floppy disk drives to be
connected. This function is especially valuable for notebook computer
applications.
Winbond W83877TF/TG provides functions that comply with ACPI (Advanced
Configuration and Power Interface), which includes support of legacy
and ACPI power management through SMI or SCI function pins. One
24-bits power management timer is implemented with the carry notify
interrupt. W83877TF/TG also has auto power management mode to reduce
the power consumption.
The serial IRQ for PCI architecture is supported, ISA IRQs
(IRQ1~IRQ15) can be cascaded into one IRQSER pin. W83877TF/TG also
features ISA bus IRQ sharing and allows two or more devices to share
the same IRQ pin.
W83877TF/TG is made to fully comply with Microsoft PC97 Hardware
Design Guide. IRQs, DMAs, and I/O space resources are flexible to
adjust to meet ISA PnP requirement. Moreover W83877TF/TG is made to
meet the specification of PC97's requirement in the power management:
ACPI and DPM (Device Power Management).
The configuration registers support mode selection, function
enable/disable, and power down function selection. Furthermore, the
configurable PnP registers are compatible with the Plug-and-Play
feature demand of Windows 95 , which makes system resource allocation
more efficient than ever.
Another benefit of W83877TF/TG is that it is pin-to-pin compatible to
W83877F, and all of the 100-pin Winbond I/O IC family. Thus makes the
design of applications very convenient and flexible.
***Versions:...
***Features:...
**W83977F/G/AF/AG WINBOND I/O (Multi I/O) c97...
**W83977TF WINBOND I/O (Multi I/O) c97...
**W83977EF WINBOND I/O (Multi I/O) <98...
**W83977ATF WINBOND I/O (Multi I/O) <98...
**
**Disk Controller:
**W83759/A/F/AF Advanced VL-IDE Disk Controller <96...
**W83769 Local Bus IDE Solution <94...
**
**UARTS:
**W86C250A UART (equivalent of INS8C250A) [no datasheet]
**W86C450/P Universal Asynchronous Receiver/Transmitter <Jul89...
**W86C451 I/O controller for IBM PC/AT/XT <Jul89...
**W86C452 I/O controller for IBM PC/AT Jul89...
**W86C456 I/O controller [no datasheet] ?
**W860551/P UART with FIFO and Printer Port Controller <94...
**
**Other:...
*ZyMOS...
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