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**82496/491     Cache Controller / Cache RAM (for P5 Pentium) 03/22/93
***Notes:
Date source: TimelineDateSort7_05.pdf

Information taken from: 
            1995_Intel_Pentium_Processors_and_Related_Components.pdf*
                                         8249x Cache controllers.pdf**

>*  Datasheet dated Oct'93
>** Datasheet undated, whole document dated '95

The info and features section have  been solely sourced from the first
source.   The  second source  provides  far  more detail.   Additional
information in  the configurations section  has been sourced  from the
second.

This  chip was  used on  the Pentium  66MHz CPU  complexes of  Intel's
Xpress platform.   Specifically the  BXCPUPENT66 (Single  66MHz, eight
82491s) and BXCPU2XPENT (Dual 66 MHz,  eight 82491s). Also found on P5
60/66MHz CPU complexes of IBM 9595/PC Server 300/500 systems.

***Info:...
***Configurations:...
***Features:...
**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:
Chips:
[82454NX] (PXB) [82453NX] (MUX) 
[82452NX] (RCG) [82451NX] (MIOC) 
[82371EB] (PIIX4E),                            
CPUs:          Single/Dual/Quad P-II Xeon/P-III Xeon
DRAM Types:    FPM EDO 2-way Interleave 4-way Interleave
Mem Rows:      8
DRAM Density:  16Mbit 64Mbit
Max Mem:       8GB
ECC/Parity:    Both
AGP speed:     N/A
Bus Speed:     100
PCI Clock/Bus: 1/3


**?????  (Profusion)    c:99...
**800 series...
*Headland/G2...
**HT21          386SX/286 Single Chip (20 MHz)                 c:Aug91
***Info:
The HT21  is an  advanced PC/AT compatible,  single-chip 80386SX/80286
design solution.   This highly  integrated single chip  allows simple,
low cost  system design options while featuring  high performance, low
power  consumption,  and minimum  board  space requirements.  Advanced
memory management features  include support for page mode,  2 or 4-way
interleaving in  both pipelined and  non-pipelined modes. The  LIM 4.0
hardware implementation  features dual sets of 32  registers with full
context support for highest performance Optimization of extended local
memory  accesses. An  advanced  EMS hardware  write-protect option  is
provided. The HT21 supports 256K and 1M DRAMs in l by 1, 1 by 4, and 1
by 9 device configurations for up  to 8MB of on-board system memory. A
flexible Shadow  RAM option for  System and Video  BIOS as well  as 8-
16-bit BIOS Options adds to overall design versatility.

A  complete PC/AT  compatible  system with  advanced  features may  be
implemented with minimal external support logic. The HT21 performs all
CPU  and peripheral support  functions in  a single  chip.  Integrated
device  functions include  DMA Controllers,  a Memory  Mapper, Timers,
Counters, Interrupt  Controllers, a Bus Controller  and all supporting
circuitry for PC  core logic requirements. The chip  also contains all
the  necessary  address buffers,  data  transceivers, memory  drivers,
parity  checking   and  supporting  circuitry  for   a  complete  high
performance computer solution. An asynchronous AT Bus clock allows for
a constant 8MHz Bus clock rate for highest bus device compatibility as
defined in  IEEE Spec P996.   In controlled bus applications  the HT21
supports up to a  12 MHz Bus Clock rate. This device  is packaged in a
208-pin Plastic Quad Flat Pack combining several external buffers into
this space saving solution.

***Configurations:...
***Features:...
**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...
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