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**A note on VESA support of 486 chipsets.
Many chipsets state  that they support VESA local  bus.  In some cases
these actually  implement VLB somewhat  like PCI, where it  is entirly
decoupled from the CPU bus. Chipsets  that do not state they work with
VLB,  may  be found  on  motherboards  that  contain VLB  slots.   VLB
is  *basically*  The 486  CPU  pinout in  a  slot  form. Unless  these
m/boards contain  some additional  chips, there VLB  implementation is
directly coupled to the CPU.

**Datasheets:...
*_IBM...
*ACC Micro...
*ALD...
*ALi...
*AMD . . . . . . . [no datasheets, some info]...
*Chips & Technologies...
**CS4041/5 CHIPSet                  (84041/84045)              2/10/95
***Info:
The  CS4041 is  the first  product in  the GreenCHIPS  CHIPSet product
portfolio  of Chips  and Technologies,  Inc.  It  provides all  of the
system  logic  for  implementing   a  high  performance,  Energy  Star
compliant 486 PC/AT design, while maintaining an extremely competitive
cost structure. The powerful feature set includes the CHIPS "standard"
system  blocks and  offers a  new  level of  system integration  while
addressing  the  ever  evolving  requirements that  the  market  place
demands. It is 100% PC/AT  compatible and directly supports the 486DX,
486DX2, 486DX4, 486SX  and 486 derivatives that support  the CPU write
back cache architecture.

The high performance CHIPSet consists of the F84041 Systems Controller
and F84045 GreenCHIPS IPC. The F84041 System Controller is packaged in
a   208-pin    PQFP   and   integrates   the    major   system   logic
functions.  Included  in  the   F84041  is  the  CHIPS  patented  Page
Interleave  DRAM  controller, high  performance  cache controller,  VL
local bus  controller, ISA bus controller, power  management module, a
local bus IDE controller and fully compatible 8042 keyboard controller
with PS/2 mouse support. The companion F84045 is packaged in a 100 pin
PQFP  and   contains  the  industry   standard  Integrated  Peripheral
Controller (IPC) which includes the DMA controllers, timers, interrupt
controllers and real time clock.

The enhanced feature set of  GreenCHIPS DRAM and cache controllers are
perfect  for   today's  High  Performance  PC/AT   designs.  The  page
interleave DRAM controller offers  high performance as well as extreme
flexibility in  supporting 486 memory subsystems.  The DRAM controller
supports up to eight banks of memory that can be configured with 256K,
1M, 4M or 16M memory  devices. Page interleaving, timing modes, memory
mix options,  direct drive support  and block by block  parity support
can  be tuned to  meet the  most optimum  requirements for  the system
design. In  addition, the high performance  secondary cache controller
provides  options  that can  be  optimized  for  performance, cost  or
both.   The  direct   mapped  cache   architecture   employs  internal
comparators  with external TAG  and data  SRAM that  can operate  in a
write-through  or write-back  mode. Cache  sizes  from 64K  to 1M  are
supported with  flexible single bank  or dual bank support  that allow
flexible timing mode selection based on CPU speed and SRAM speed.

The  "Green" in  GreenCHIPS comes  from the  Power  management support
integrated in  the CHIPSet. The  CS4041 provides the perfect  level of
power management support for  Energy Star compliant desktops. Included
in the  power management section  is direct support for  SMM operation
and clock switching for the popular 486 derivatives. Two event timers,
programmable I/O  pins, I/O  restart and programmable  event detection
provide a  wide range  of options for  power management  selection and
customization.

The CS4041 provides new levels of integration in system logic CHIPSets
by providing  a local bus  IDE interface and keyboard  controller. The
robust local bus IDE interface  is decoupled from the AT state machine
and  does not  use a  VL local  bus load.  The interface  is versatile
enough to support  up to eight IDE drives allowing  each drive to have
unique command settings.  The result is the best  performance for each
drive type  allowing significant  performance gains over  the standard
ISA  interface. This  is accomplished  without any  compromise  to the
standard VL local bus.

CPUs Supported
oIntel 486 CPUs
oAMD 486 CPUs
oCyrix 486 CPUs
oIBM 486 CPUs
oL1 (CPU) write back cache fully supported
oSMI support (both Intel and Cyrix)
oClock Frequencies:
 25MHz, 33MHz, 40MHz,  50MHz

***Configurations:...
***Features:...
**CB8291   ELEAT                    [no datasheet]                 c90...
**CB8295   ELEATsx                  [no datasheet]                 c90...
**82C100   IBM PS/2 Model 30/Super XT                                ?...
**82C110   IBM PS/2 Model 30/Super XT                                ?...
**82C235   Single Chip AT (SCAT)                                   c89...
**82C836   Single Chip 386sx (SCATsx)                              <91...
**F8680/A  PC/CHIP Single-Chip PC                                  c93...
**
**Support Chips:
**64200    (Wingine) High Performance 'Windows Engine'         c:Oct91...
**82C206   Integrated Peripheral Controller                        c86...
**82C601/A Single Chip Peripheral Controller                 <08/30/90...
**82C607   Multifunction Controller                             <Jun88...
**82C710   Universal Peripheral Controller                     c:Aug90...
**82C711   Universal Peripheral Controller II                  c:Jan91...
**82C712   Universal Peripheral Controller II                  c:Jan91...
**82C721   Universal Peripheral Controller III                 c:May93...
**82C735   I/O Peripheral Controller With Printgine            c:Jul93...
**82C835   Single CHIP 386sx AT Cache Controller               c:Apr91...
**F87000   Multi-Mode Peripheral Chip                         11/23/93...
**Other:...
**Disk:...
**Video:...
*Contaq  . . . . . [no datasheets, some info]...
*Efar Microsystems [no datasheets, some info]...
*ETEQ...
*Faraday...
*Forex . . . . . . [List only, no datasheets found]...
*Intel...
**82485       Turbo Cache (and 485Turbocache)                      c90
***Notes:...
***Info:
The 82485 is  a second-level cache controller designed  to improve the
performance  of  Intel486  Microprocessor  systems.  One  82485  cache
controller supports  64K or  128K bytes of  second level  cache memory
that maps  to the  entire 4 Gigabytes  of the  Intel486 microprocessor
address space. The controller  is completely software transparent. One
controller plus SRAMs  provides a 64K or a  128K cache. External EPROM
can  be  cached  yet  remain  write protected.   The  82485  is  fully
compatible  with the  Intel486  microprocessor. All  Intel486 CPU  bus
cycles and timings are supported.

A complete, optional second level  cache controller using the 82485 is
available  as the 485Turbocache  Module from  Intel (data  sheet order
number 240722).

2.0 FUNCTIONAL DESCRIPTION
2.1 Introduction
The 82485 is a single ported, two-way set associative cache controller
designed specifically  to interface with  the Intel486 microprocessor.
The controller supports either a sectored configuration (two lines per
tag) or  a non-sectored configuration  (one line per tag).   The 82485
will directly support a nonsectored  64K data cache or a 128K sectored
data cache.  Both the 64K and  128K configurations are able to map the
entire 4 gigabytes of  the Intel486 microprocessor address space.  The
82485 interfaces directly to  the Intel486 microprocessor.  All Intel-
486 CPU bus cycles and timings are supported.  The 82485 also supports
0 wait  state processor operation  when there is  a cache hit  and has
provisions to support invalidation cycles, BOFF# cycles, and premature
BLAST# terminations.  The controller  is look aside (monitors bus act-
ivity in parallel to the processor) and write through (all writes pro-
pagate to the  system bus), so it supports  the same cache consistency
mechanisms as the  Intel486 CPU.  The controller also  provides a safe
method to cache ROM BIOS through the  use of a write protect pin and a
write protect strapping option.

The data cache  (Static RAM) resides external to  the 82485. The 82485
provides all  controls for  the SRAMs.  No  external latches  or tran-
ceivers are  required.  The 82485  output buffers support up  to eight
SRAMs.  A  64K cache can be  designed with only  five components; nine
components for a 128K cache.  Two-way set associativity is provided by
dual banked SRAMs. Data parity is supported.

The  82485  can  be  used  to  design  a  custom  second  level  cache
configuration. For an easier system design and higher integration, the
82485M Turbocache  can be used  (see data sheet order  number 240722).
This  module is  a  complete second  level  cache in  one package.  It
consists  of a single  82485 cache  controller and  SRAM to  provide a
complete 64K or 128K second level Intel486 microprocessor second level
cache.

***Versions:...
***Features:...
**82489DX       Advanced Programmable Interrupt Controller    10/12/92...
**82495DX/490DX DX CPU-Cache Chip Set                           <Sep91...
**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...
*HMC (Hulon Microelectronics)...
*Logicstar...
*Motorola...
*OPTi...
*PC CHIPS/Amptron/Atrend/ECS/Elpina/etc...
*SIS...
*Symphony...
*TI (Texas Instruments)...
*UMC...
*Unresearched:...
*VIA...
*VLSI...
*Western Digital...
*Winbond...
*ZyMOS...
*General Sources:...

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