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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...
**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
***Notes:...
***Info:...
***Configurations:...
***Features:...
**
**Later chipsets (basic spec):
**440 series:...
**450NX (?) 06/29/98:...
**????? (Profusion) c:99...
**800 series...
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*VIA...
**VT82C496G Pluto, Green PC 80486 PCI/VL/ISA System <05/30/94
***Info:...
***Configurations:...
***Features
1. Fully IBM PC/AT Compatible
2. Flexible CPU and Local Bus Interface
- Supports 80486SX/DX/DX2/DX4 and compatible CPUs
- CPU speed up to 100 Mhz including 80486DX-50, 80486DX2-66 and
80486DX4-100
- Supports CPUs with write-back internal cache, e.g. P24D, P24T
and Cx486DX/DX2
- Snoop filtering for write-back CPUs
- Supports SMI protocols of Intel, AMD, TI and Cyrix CPUs
- CPU clock stretching and throttling
- Zero frequency and zero voltage CPU suspend
- Soft and hard CPU reset
- Direct VESA and other local bus interface with DMA/master access
- Built-in arbitration for two local bus masters
3. Advanced Cache Controller
- Write back/write through scheme
- Direct map scheme
- Flexible cache size: 0K/32K/64K/128K/256K/512K/1MB
- One bank or two banks of data independent of cache size
- Integrated 8-bit tag comparator
- Interleaved SRAM access to achieve 2-1-1-1 burst fill
- Supports burst read and burst write transfers
- System and video BIOS cacheable and write-protect
- Programmable cache timing
- Programmable non-cacheable region
- Optional combined tag and alter bit SRAM for the write-back
scheme
- Eight bit tag under the combined tag-alter scheme without
sacrifice of cacheable space
4. Fast Page Mode DRAM Controller
- Mixed 256K/512K/1M/2M/4M/8M/16MxN DRAMs
- 8 banks up to 128MB
- Flexible column and row addresses
- 30 pin (x9) and single/double density 72 pin (x36) SIMM
module support
- Programmable DRAM timing
- BIOS shadow at 16KB increment
- 256/384K memory relocation
- System management memory remapping
- Decoupled DRAM refresh with staggered RAS timing
- CAS-before-RAS and slow refresh
5. Synchronous ISA Bus Controller
- Synchronous ISA bus clock
- Programmable wait state, command delay and IO recovery time
- Bus conversion and data alignment
- Hardware and software de-turbo control
- Fast reset and Gate A20 operation
- Integrated 82C206 peripheral controller
- Edge trigger or level sensitive interrupt controller
- Flash EPROM and combined BIOS support
6. Integrated Power Management Unit
- Normal, conserve, doze, sleep and suspend modes
- System event monitoring with two event classes and two idle
timers
- Primary and secondary interrupt differentiation for individual
channels
- One extended peripheral timer and one general purpose timer
- Automatic conserve mode operation for short and frequent system
idleness
- Modular clock and modular power
- CPU clock stretching, throttling or stop without affecting the
ISA bus clock
- Zero frequency operation with automatic resume
- Zero volt operation with leakage control
- Four general purpose IO or power control ports
- APM 1.1 compliant
7. Integrated Local Bus IDE Controller
- 32-bit host data transfer
- Mode-3 transfer capabilities (>10MB/s)
- Programmable read/write, master/slave and active/recovery timing
in units of CPU clock
- Prefetch and write buffers
- Support either primary (1F0-1F7h) or secondary (170-177h)
channel with two devices
- No external logic required
8. High Integration and Complete Functionality
- Glueless interface with the VT82C406MV IXP (Integrated X-bus
Peripheral Controller, 100PQFP) to eliminate the multi-clock
generator, the keyboard controller with PS2 mouse, the DS-1285
style real time clock with extended CMOS RAM and the address
buffers.
- 9 TTLs for a complete main board implementation
- Optional VT82C505 (160 PQFP) to bridge a VL/ISA system to the
PCI bus
9. 0.8um high speed and low power CMOS process
10. 208-pin PQFP package
**VT82C530MV 3.3V Pentium chipset [no datasheet, some info]<05/30/94...
**VT82C570M Apollo Master, Green Pentium/P54C <06/22/95...
**VT82C580VP Apollo VP, Pentium/M1/K5 PCI/ISA System <02/15/96...
**VT82C580VPX Apollo VPX, VPX/97, Pentium with 66/75MHz Bus <01/09/97...
**VT82C590 Apollo VP2, VP2/97, Single-Chip Pentium 66MHz <01/10/97...
**VT82C597/AT Apollo VP3, Single-Chip for Pentium with AGP <10/03/97...
**VT82C598MVP Apollo MVP3,Single-Chip 66/75/83/100MHz & AGP <09/22/97...
**VT8501 Apollo MVP4,Single-Chip 66-100MHz & AGP <11/04/98...
**VT82C680 Apollo P6, Pentium-Pro Chip Set <08/30/96...
**Support chips:
**VT82C505 Pentium/486 VL to PCI Bridge <05/30/94...
**VT82C586/A/B PCI Integrated Peripheral Controller <10/13/96...
**VT82C596/A Mobile PCI Integrated Peripheral Controller <11/05/97...
**VT82C686A/B PCI Super-I/O Integrated Peripheral Ctrl. <02/10/98...
**Later P-Pro/II/III/Celeron...
**Later AMD...
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