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**82395SX     Smart Cache                                     12/17/90
***Notes:...
**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...
**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:
o   Highly Integrated, Single Chip 80386SX AT Compatible Solution
o   Special Multiple Context Hardware EMS Support (LIM 4.0 compatible) 
    using 2 sets of 32 EMS Registers
o   Single or Dual BIOS
o   Shadow RAM support over entire C0000 to DFFFF Address range in 16K 
    increments, E0000 to FFFFF in 64K increments
o   Page Mode and 2-way Interleaving
o   Supports up to 12MHz AT Bus Clock
o   High Performance Muxed DRAM Interleave
o   Programmable DRAM timing
o   Asynchronous AT Bus Clock
o   Three-State Test Mode
o   16-Bit ROM BIOS Support

HT 18A/B Special Features
o   16 and 20 MHz CPU Clock Speeds
o   Supports up to 8M CPU Memory using combinations of 64K, 256K and 
    1M Devices
o   4 Bank, 4-way Interleave Mode

HT18C/25MHz Special Features
o   16, 20 and 25MHz CPU Clock Speeds
o   Supports up to 20M with EMS CPU Memory using combinations of 256K, 
    1M and 4M Devices

**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
***Info:
The  HT44 is  a  look-aside write-through,  80486SX,  486DX or  486DX2
secondary cache  controller. It is  packaged in an  inexpensive 84-pin
plastic-leaded chip carrier (PLCC).

Architecture
With  its look-aside architecture,  the HT44  fits beside  the CPU-to-
Memory bus  and not in  the data path.   Therefore, once the  HT44 has
been designed  into a  486 system, it  can be populated  for secondary
cache systems or left vacant for non-secondary cache systems. The HT44
is direct-mapped to the available address space.

Performance
The  HT44  has a  number  of  performance  enhancing features.   These
include zero-waitstate burst line fills  to the 486 on secondary cache
hits, and simultaneous 486 and secondary cache updates on read misses.

Memory Configurations
The HT44 supports  cache sizes from 32KBytes to  1MB. Both synchronous
and asynchronous  SRAMs are supported.  25ns SRAMs are  sufficient for
zero-wait-state operation at 33MHz.

Chip Set Support
The HT44 can,  be implemented with minimal glue logic  in a 486 system
with the  HTK340 (code  name Shasta) chip  set.  The registers  in the
HTK340  allow  for programming  of  non-cacheable and  write-protected
areas of  memory. The  HTK340 will support  the HT44  with synchronous
SRAMs only.   Future Headland chip sets will  support both synchronous
and asynchronous SRAM designs.

The HT44  can also be used  with some third-party  chip sets, however,
additional glue logic may be required.

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