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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...
**SL9090/A Universal PC/AT Clock Chip <oct88
***Info:
The SL9090 is a Universal Clock Chip capable of generating all
essential clock signals that are used in a typical P.C. design. This
device can support 8086, 8088, 80286, 803865X, 80386DX and 80486
microprocessor based designs. The outputs of this clock chip are
programmable through the keyboard and also by jumper settings. Clock
options of 60 MHz, 50 MHz, 48 MHz, 40 MHz, 32 MHz and their multiples
are available, in order to give flexibility to the user.
Frequency selection is done by the three decode inputs FS0-FS2 as
shown in Table 1. [see datasheet] FSEL is used to control the system
I/O bus clock. During a CPU cycle the FSEL remains high, and the
frequency selection on the outputs is determined by the FS0-FS2
pins. When an I / O cycle is detected, the FSEL goes low and fixed
frequencies of 16 MHz, 8 MHz and 4 MHz are available on output pins
F12 (pin 8), F122 (pin 5) and F124 (pin 3). Designer have an option to
run the system I/O clock at half the CPU clock as well. This is
achieved by connecting the FSEL pin to the keyboard controller in
order to hold this pin high during an I/O cycle. This allows the FSEL
signal to be controlled through the keyboard by pressing CTL ALT +" or
"CTL ALT-".
The reference frequency of 14.318 MHz is also supplied to the output
through the FREF pin for the I/O slots. This frequency is divided by 2
internally and 7.159 MHz is supplied to the output through the FREF2
pin for the keyboard controller. The FREF12 pin has an output of 1.19
MHz and is used by the timerl (8254) in the peripheral controller for
refresh. All outputs are capable of 8mA drive.
The SL9090 consists of two independent Voltage controlled Oscillators
(VCOs) integrated with dividers, phase sensitive detectors, charge
pumps and buffer amplifiers to provide the desired glitch free
frequencies. An externally generated signal of 14.318 MHz is used as
the reference frequency for the SL9090. This reference frequency is
fed into the phase sensitive detectors to differentiate the difference
in phase between the reference frequency being generated by the
VCOs. This becomes an input to the charge pumps which in turn
generates a signal to sink or source the charge. This signal is
buffered by the buffer amplifiers between the charge pumps and the
VCOs. The output from the VCOs are divided to generate the appropriate
outputs.
The SL9090 is designed, using advanced Bipolar technology and is
available in a 44 pin PLCC. It requires only one crystal (14.3 MHz)
and a few RC components to generate all the essential clocks that are
required for a PC. design. As there is only one crystal on the system
board, the Electro Magnetic Radiation is reduced significantly
facilitating FCC approval. This makes the SL9090 an ideal low cost
solution with capabilities for universal applications.
***Versions:...
***Features:...
**SL9095 Power Management Unit ?...
**SL9151 80286 Page Interleave Memory Controller (16-25MHz) ?...
**SL9250 80386SX Page Mode Memory Controller (16/20MHz 8MB) ?...
**SL9251 80386SX Page Interleave Memory Controller <04/13/90...
**SL9252 80386SX System and Memory Controller <06/12/90...
**SL9350 80386DX Page Mode Memory Controller (16-25MHz 16MB) ?...
**SL9351 80386DX Page Interleave Memory Controller (33MHz) ?...
**SL9352 80386DX System and Memory Controller <06/12/90...
**SLXXXX Other chips...
**
**VT82C470 "Jupiter", Chip Set (w/o cache) 386 [no datasheet] ?
**VT82C475 "Jupiter", Chip Set (w/cache) 386 [no datasheet] ?
**VT82C486/2/3 "GMC chipset" [no datasheet, some info] ?...
**VT82C495/480 "Venus" Chip Set [no datasheet] ?
**VT82C495/491 ? EISA Chip Set [no datasheet, some info] <93...
**VT82C496G Pluto, Green PC 80486 PCI/VL/ISA System <05/30/94...
**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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