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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...
**UM82C230 286AT MORTAR Chip Set <91
***Info:
The UMC's MORTAR (286AT) Chip Set UM82C230 series provides an economic
alternative for building a reliable IBM PC/AT compatible system. A
commercial 12MHZ/0 wait state, 4MByte main memory system and
math-coprocessor can be easily built by using 3 VLSIs, 8 logic
components plus memory and processor.
The UM82C230 MORTAR chipset consists of the UM82C231 System/Memory
Controller, the UM82C232 Data/Address Buffer and the UM82C206
Integrated Peripherals Controller (IPC).
As shown in the System Block Diagram, [see datasheet] there are three
data buses: local data bus, AT data bus and peripheral data (XD) bus.
The local DRAM, EPROM and Numerical Processor are located on the local
data bus. The UM82C206 and 8042 Keyboard Controller sit on the XD bus.
The AT data bus was driven by the UM82C232 directly which conveys the
data to/from the AT Channel Adaptors.
The address bus architecture is also very simple; local CPU address
bus, local DRAM address bus (MA), peripheral address bus (XA) and AT
address bus. The local address bus is shared between CPU, UM82C231 and
UM82C206. The MA bus is used by the local DRAM only. Most of the
system board devices are attached to the XA bus, like UM82C232,
UM82C206, ROMs and 8042. Some AT address lines are driven by the
UM82C231 or UM82C232 directly; the others are buffered.
The UM82C231 provides synchronization and control signals for all
buses. The UM82C231 also distinguishes if the current cycle is local
memory cycle. Upon detecting that it is a local DRAM cycle, no AT
control signals are sent out to the AT channel. The UM82C231 is based
on the memory configurations to complete the current cycle with
fastest response. If the cycle is AT cycle, the UM82C231 sends out the
control signals sequentially which are then used by the adaptors or
system board devices to receive the write data or to send the fetched
data. Then, depending on the status signals sent back by the adaptors
or system board devices, the UM82C231 determines which kind of AT
cycles to perform: 8-bit, 16-bit, bus conversion, wait state insert,
or wait state cycle.
The UM82C232 Data/Address buffer provides the buffering and latching
between the CPU local data bus, AT bus and XD bus. The parity bit
generation and parity bit checking logic resides in the UM82C232 also.
During DMA cycles, the UM82C232 latches the address from XD, which is
sent by the UM82C206, and transfers to XA bus.
***Configurations:...
***Features:...
**UM82C210 386SX/286 AT Chip Set <91...
**UM82C3xx Twinstar & UM82C336F/N & UM82C39x [no datasheet] ?...
**UM82C380 386 HEAT PC/AT Chip Set <91...
**UM82C480 386/486 PC Chip Set c91...
**UM82C493/491 ??????????????? [no datasheet] ?...
**UM8498/8496 486 VL Chipset "Super Energy Star Green"[no dsheet]c94...
**UM8881/8886 HB4 PCI Chipset "Super Energy Star Green"[no dsheet]c94...
**UM8890 Pentium chipset [no datasheet] ?...
**
**Support Chips:
**UM82152 Cache Controller (AUStek A38152 clone) <91...
**UM82C852 Multi I/O For XT <91...
**UM82C206 Integrated Peripheral Controller <91...
**UM82c45x Serial/Parallel chips ?...
**Other chips:...
*Unresearched:...
*VIA...
*VLSI...
*Western Digital...
*Winbond...
*ZyMOS...
*General Sources:...
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