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**82420TX/ZX PCIset (for 486) TX (Saturn), ZX (Saturn II) c:Nov92
***Notes:
Date source: 82420 (nov92).pdf
Originally known as the 82420 chipset
Information taken from: 82420 (nov92).pdf
82420_PCIset_ISA_and_EISA_Bridges_Mar93.pdf
Intel_Peripheral_Components_1994.pdf*
82424ZX (nov94).pdf, 82420 (nov94).pdf
(Errata:1) http://support.intel.com/support/chipsets/420/8510.htm**
(Errata:2) http://support.intel.com/support/chipsets/420/8511.htm**
(Errata:3) http://support.intel.com/support/chipsets/420/8512.htm**
(Errata:4) http://support.intel.com/support/chipsets/420/8513.htm**
(Errata:5) http://support.intel.com/support/chipsets/420/apptech.htm**
>* General 82420 datasheet, 82423 and 82424 all dated Oct'93.
>** see archived sources at the end of this section
Differences:
Nov'92 to Mar'93:
The Mar'93 datasheet (Both only include the general section) has a
completely restructured Info and Features section. The main func-
tional difference is that in the Nov'92, no PCI-EISA bridge version
is available. The Mar'93 is the earliest datasheet found that
mentions the 82374/82375 EISA components.
Mar'93 to Oct'93:
The Mar'93 datasheet refers to the 82424TX component directly, the
Oct'93 to just 82424. Same with 82423TX and 82423. This is due to
the datasheet specifying both the TX and ZX variants of both chips.
A similar thing occurs with the 82378IB and 82378. In Oct'93 there
were IB and ZB variants. Other differences are shown in the text.
The Mar'93 source only includes the general section. In Oct'93, both
datasheets found for the specific chips are only short 1-2 pages
long.
In Errata:1, more specifics are given, that partially contradict the
Oct'93 datasheet. Dated Aug'93 the following differences are given:
"
82424TX * Name change from 82424TX to 82424ZX
Changes: * ZX eliminates all known TX errata
* Features/Enhancements include: Extra RAS line supports
additional memory, Optional memory locations for SMM,
external work-around logic for TX eliminated
Timing:
We anticipate production shipments...in October 1993 for the
82424ZX. "
Errata:2 gives further details. The document itself is undated, but
Errata:1 is hyperlinked to it. Its text is quoted in the Versions
section. Errata:3 & 4 go into further detail.
All Errata documents contradict the Oct'93 datasheet, by making no
mention of the 82423ZX variant.
Oct'93 to Nov'94:
In the Nov'94 datasheet specific variants are now referred to again.
All references to 82424 are replaced with 82424ZX, 82378 replaced
with 82378ZB. The 82423 is replaced with 82423TX again. It appears
the 82423ZX variant either no longer exists, or the Oct'93 datasheet
refers to a chip that was planned, but never introduced. As the
Oct'93 datasheet for the 82423 specific chip is only a part data-
sheet (1-2 pages), it has been impossible to determine what the
differences are between the ZX and TX variants, or even if the ZX
variant actually existed. It simply states there are differences.
The specific datasheet for the 82424 now only refers to the ZX
variant. the ZX-50 variant is not mentioned. Other changes between
the datasheets are shown in the text.
Errata:5 contains links to additional information, some related to
this chipset.
Archived sources:
http://web.archive.org/web/20000816013859/http://support.intel.com/support/chipsets/420/8510.htm
http://web.archive.org/web/20000816013854/http://support.intel.com/support/chipsets/420/8511.htm
http://web.archive.org/web/20000818162626/http://support.intel.com/support/chipsets/420/8512.htm
http://web.archive.org/web/20000818162634/http://support.intel.com/support/chipsets/420/8513.htm
http://web.archive.org/web/19990421055226/http://support.intel.com/support/chipsets/420/apptech.htm
***Info:...
***Versions:...
***Configurations:...
***Features:...
**82420EX PCIset (for 486) EX (Aries) (82425EX/82426EX) <Dec94...
**82430LX PCIset (Pentium) LX (Mercury) (82433LX/82434LX) 03/22/93...
**82430NX PCIset (Pentium) NX (Neptune) (82433NX/82434NX) Mar94...
**82430FX PCIset (Pentium) FX (Triton I) (82437FX/82438FX)01/31/95...
**82430MX PCIset (Pentium) MX (Mobile Triton)(82437/438MX)11/01/95...
**82430HX PCIset (Pentium) HX (Triton II) (82439HX) 02/12/96...
**82430VX PCIset (Pentium) VX (Triton II) (82437VX/82438) 02/12/96...
**82430TX PCIset (Pentium) TX (Triton II) (82439TX) 02/17/97...
**82450KX/GX PCIset (Pentium Pro) KX/GX (Mars/Orion) 11/01/95...
**
**Support Chips:
**82091AA Advanced Interface Peripheral (AIP) c93...
**8289 Bus Arbiter (808x) c79...
**82289 Bus Arbiter for iAPX 286 Processor Family c83...
**82258 Advanced Direct Memory Access Coprocessor(ADMA) 01/01/84...
**82335 High-Integration Interface Device For 386SX c:Nov88...
**82360SL I/O Subsystem 10/05/90...
**82370 Integrated System Peripheral (for 82376) c:Oct88...
**82371FB/SB PCI ISA IDE Xcelerator 82371FB/82371SB (PIIX/3) 01/31/95...
**82371MX Mobile PCI I/O IDE Xcelerator (MPIIX) 11/01/95...
**82371AB PCI-TO-ISA / IDE Xcelerator 82371AB (PIIX4) 02/17/97...
**82374/82375 PCI-EISA Bridge (82374EB/82375EB, 374SB/375SB) c:Mar93...
**82378 System I/O (SIO) (82378IB and 82378ZB) c:Mar93...
**82379AB System I/O-APIC (SIO.A) <Dec94...
**82380 32-bit DMA Controller w/ Integrated Peripherals 02/01/87...
**82380FB/AB PCIset: 82380FB Mobile PCI-to-PCI Bridge(MPCI2) 02/17/97...
**82384 Clock Generator and Reset Interface c86...
**82385 32-bit Cache Controller for 80386 09/29/87...
**82385SX 32-bit Cache Controller for 80386SX 01/25/89...
**82395DX High Performance Smart Cache 06/18/90...
**82395SX Smart Cache 12/17/90...
**82396SX Smart Cache 12/17/90...
**82485 Turbo Cache (and 485Turbocache) c90...
**82489DX Advanced Programmable Interrupt Controller 10/12/92...
**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...
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*SIS...
*Symphony...
*TI (Texas Instruments)...
*UMC...
*Unresearched:...
*VIA...
*VLSI...
*Western Digital...
*Winbond...
*ZyMOS...
*General Sources:...
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