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**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)...
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*OPTi...
**82C693/6/7     Pentium uP Write Back Cache EISA                 c:93
***Notes:...
***info:...
***Configurations:...
***Features:...
**82C700         FireStar                                         c:97...
**82C701         FireStar Plus                                    c:97...
**82C750         Vendetta      [no datasheet]                        ?...
**82c801         SCWB2 DX Single Chip Solution                    c:92...
**82C802         SCWB2 PC/AT Single Chip [no datasheet]              ?...
**82C802G/GP     System/Power Management Controller (cached)      c:93...
**82C895         System/Power Management Controller (cached)   c:Sep94...
**82C898         System/Power Management Controller (non-cache)c:Nov94...
**
**Support Chips:
**82C601/2       Buffer Devices                                 <Nov94...
**82C822         PCIB (VLB-to-PCI bridge)                         c:94...
**Other:...
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*SIS...
*Symphony...
**SL82C365    Cache Controller (for 386DX/SX)                     c:91
***Info:
The SL82C365 supports direct-mapped cache system with data size ranged
from  16KB to  1MB  and line  size  ranged from  1  to 4  doublewords.
Without any  external logic, SL82C365 supports  1 to 4  banks of cache
SRAMs  independent of  the  line  size.  An  8-bit  tag comparator  is
integrated into the  chip which not only saves on  the system cost but
also improves  the overall performance.   25ns tag SRAM and  35ns data
SRAM   are  adequate   for   zero  wait   state  non-pipelined   33Mhz
operation. Assuming  8Kx8, 16Kx4, 32Kx8  and 64Kx4 SRAMs are  used for
tag SRAM, the selectable organization  is indicated in Table 1-1. [see
datasheet]  More options  are  available for  data RAM  configurations
because of the flexibility in  selecting the number of banks. Refer to
section 1.13 [see datasheet] for detailed design examples.

***Versions:...
***Features:...
**SL82C465    Cache Controller (for 486/386DX/SX)                 c:91...
*TI (Texas Instruments)...
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