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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...
**
**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...
**VT82C580VP Apollo VP, Pentium/M1/K5 PCI/ISA System <02/15/96
***Info:...
***Configurations:...
***Features:
o PCI/ISA Green PC Ready
o High Integration
- VT82C585VP system controller
- VT82C586 PCI to ISA bridge
- Two instances of the VT82C587VP data buffers
- Six TTLs for a complete main board implementation
o Flexible CPU Interface
- 64-bit P54C, K5 and M1 CPU interface
- CPU external bus speed up to 66Mhz (internal 200Mhz and above)
- Supports CPU internal write-back cache
- Concurrent CPU/cache and PCI/DRAM operation
- System management interrupt, memory remap and STPCLK mechanism
- Cyril M1 linear burst support
- CPU NA#/Address pipeline capability
o Advanced Cache Controller
- Direct map write back or write through secondary cache
- Burst Synchronous (Pipelined or non-pipelined), asynchronous
SRAM, and Cache Module support
- Eight-pin CWE# and GWE# control options
- Flexible cache size: 0K/256K/512K/1M/2MB
- 32 byte line size to match the primary cache
- Integrated 10-bit tag comparator
- 3-1-1-1 read/write timing for Burst Synchronous SRAM access at
66Mhz
- 3-1-1-1-1-1-1-1 back to back read timing for Burst Synchronous
SRAM access at 66Mhz
- Sustained 3 cycle write access for Burst Synchronous SRAM access
or CPU to DRAM and PCI bus post write buffers at 66Mhz
- 3-2-2-2 (read) and 4-2-2-2 (write) timing for interleaved
asynchronous SRAM access at 66Mhz
- Data streaming for simultaneous primary and secondary cache line
fill
- System and video BIOS cacheable and write-protect
- Programmable cacheable region and cache timing
- Optional combined tag and alter bit SRAM for write-back scheme
o Fast DRAM Controller
- Concurrent DRAM writeback
- Four Cache lines (16 quadwords) of CPU/cache to DRAM write
buffers
- Fast Page Mode/EDO/Burst EDO/Synchronous-DRAM support in a mixed
combination
- Mixed 256K/512K/1M/2M/4M/8M/16MxN DRAMs
- 6 banks up to 512MB DRAMs (maximum four banks of Synchronous
DRAM)
- Flexible row and column addresses
- 64 bit or 32 bit data width in arbitrary mixed combination
- 3.3v and 5v DRAM without external transceivers
- Speculative DRAM access
- Read around Write capability for non-stalled CPU read
- Burst read and write operation
- 4-2-2-2 on page, 7-2-2-2 start page and 9-2-2-2 off page timing
for EDO DRAMs at 50/60Mhz
- 4-2-2-2 on page, 8-2-2-2 start page and 11-2-2-2 off page timing
for EDO DRAMs at 66Mhz
- 5-1-1-1 on page, 8-1-1-1 start page and 10-1-1-1 off page timing
for Burst EDO DRAMs at 66Mhz
- 5-2-2-2-3-1-2-2 back-to-back access for EDO DRAM at 66Mhz
- 5-1-1-1-3-1-1-1 back-to-back access for BEDO DRAM at 66Mhz
- BIOS shadow at 16KB increment
- System management memory remapping
- Decoupled and burst DRAM refresh with staggered RAS timing
- Programmable refresh rate, CAS-before-RAS refresh and refresh on
populated banks only
o Unified Memory Architecture
- Supports VESA UMA handshake protocol
- Compatible with major video/GUI products
- Direct video frame buffer access
- Satisfies maximum latency requirement from REQ# to GNT# and from
GNT# to REQ#
o Intelligent PCI Bus Controller
- 32 bit PCI interface
- Supports 66Mhz and 3.3v/5v PCI bus
- PCI master snoop ahead and snoop filtering
- PCI master Peer Concurrency
- Synchronous Bus to CPU clock with divide-by-two from the CPU
clock
- Automatic detection of data streaming burst cycles from CPU to
the PCI bus
- Five levels (double-words) of CPU to PCI posted write buffers
- Byte merging in the write buffers to reduce the number of PCI
cycles and to create further PCI bursting possibilities
- Zero wait state PCI master and slave burst transfer rate
- PCI to system memory data streaming up to 132Mbyte/sec
- Sixty-four levels (double-words) of post write buffers from PCI
masters to DRAM
- Thirty-two levels (double-words) of prefetch buffers from DRAM
for access by PCI masters
- Enhanced PCI command optimization (MRL, MRM, MWI, etc)
- Complete steerable PCI interrupts
- Supports L1 write-back forward to PCI master read to minimize
PCI read latency
- Supports L1 write-back merged with PCI master post-write to
minimize DRAM utilization
- Provides transaction timer to fairly arbitrate between PCI
masters
- PCI-2.1 compliant
o Enhanced Master Mode PCI IDE Controller
- Dual channel master mode PCI supporting four Enhanced IDE
devices
- Transfer rate up to 22MB/sec to cover PIO mode 4 and Multiword
DMA mode 2 drivers and beyond
- Sixteen levels (doublewords) of prefetch and write buffers
- Interlaced commands between two channels
- Bus master programming interface for ATA controllers SFF-8038
rev.1.0 compliant
- Full scatter and gather capability
- Support ATAPI compliant devices
- Support PCI native and ATA compatibility modes
- Complete software driver support
o Universal Serial Bus Controller
- USB v1.0 and Intel Universal HCI v1.0 compatible
- Eighteen levels(doublwords) of data FIFOs
- Root hub and two function parts with built-in physical layer
transceivers
- Legacy keyboard and PS/2 mouse support
o Plug and Play Controller
- Dual interrupt and DMA signal steering with plug and play control
- Microsoft Windows 95 and plug and play BIOS compliant
o Sophisticated Power Management Unit
- Normal, doze, sleep, suspend and conserve modes
- System event monitoring with two event classes
- One idle timer, one peripheral timer and one general purpose
timer
- More than ten general purpose Input/Output ports
- Six external event input ports with programmable SMI condition
- Complete leakage control when external component is in power off
state
- Primary and secondary interrupt differentiation for individual
channels
- Clock stretching, clock throttling and clock stop control
- Multiple internal and external SMI sources for flexible power
management models
- Two programmable output ports
- APM 1.1 compliant
o PCI to ISA Bridge
- Integrated 82C206 peripheral controller
- Integrated keyboard controller with PS2 mouse supports
- Integrated DS12885 style real time clock with extended 128 byte
CMOS RAM
- Integrated USB (universal serial bus) controller with hub and
two function ports
- Integrated master mode enhanced IDE controller with enhanced
PCI bus commands
- PCI-2.1 compliant with delay transaction
- Four double-word line buffer between PCI and ISA bus
- Supports type F DMA transfers
- Fast reset and Gate A20 operation
- Edge trigger or level sensitive interrupt
- Flash EPROM and combined BIOS support
o Built-in nand-tree pin scan test capability
o 0.6um mixed voltage, high speed and low power CMOS process
o 208 pin PQFP for VT82C585VP
o 208 pin PQFP for VT82C586
o 100 pin PQFP for VT82C587VP
**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...
**Other...
*VLSI...
*Western Digital...
*Winbond...
*ZyMOS...
*General Sources:...
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