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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...
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*Headland/G2...
**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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*UMC...
**UM82C***     (IBM/INTEL Direct replacement)                      c87
Note:  Dates vary  for when  these  chips were  first available.   Two
databooks have been used one from  '86 the other from '91. Not all the
chips  are  listed  in  the  '86  databook, the  date  of  '87  is  an
assumption.

PC/XT:
IBM:	      UMC:	  Desc:
Intel 8284    UM82C84A    25MHz CMOS Clock Generator and Driver
Intel 8288    UM82C88     Bus Controller
Intel 8259    UM8259A     Programmable Interrupt Controller also UM82C59A-2 (CMOS version)
Intel 8237    UM8237A     3-5MHz Programmable DMA Controller (DMAC)
Intel 8253    UM8253*2    2.6-5MHz Programmable Interval Timer
Intel 8255    UM82C55A*   Programmable Peripheral Interface

Note: *  indicates: possible  compatibility, datasheet does  not state
      explicitly. YMMV.

Note: *2  indicates:   The   UM8253   can   be   replaced   with   the
      UM82C54/-2. The datasheet says it is a superset of the 8253, and
      works up to 10MHz. Also it's compatible with the 8254.  AT: IBM:
      UMC: Desc: Intel 82284  UM82C284* 10-12.5MHz Clock Generator and
      Ready Interface Intel 82288  UM82C288* 10-12.5MHz Bus Controller
      Intel 8254  UM82C54/-2 8-10MHz CMOS Programmable  Interval Timer
      Intel  8259  UM8259A   Programmable  Interrupt  Controller  also
      UM82C59A-2 (CMOS version) Intel 8237 UM8237A 3-5MHz Programmable
      DMA Controller (DMAC) 74LS612 UM74HCT612* Memory Mapper MC146818
      RTC  UM82C6818* Real-Time  Clock (RTC)  Intel 8047  ??  Keyboard
      Controller

Note: *  indicates: possible  compatibility, datasheet does  not state
explicitly. YMMV.

**UM82C088     PC/XT Integration Chip                              <91...
**UM82C230     286AT MORTAR Chip Set                               <91...
**UM82C210     386SX/286 AT Chip Set                               <91...
**UM82C3xx     Twinstar & UM82C336F/N & UM82C39x [no datasheet]      ?...
**UM82C380     386 HEAT PC/AT Chip Set                             <91...
**UM82C480     386/486 PC Chip Set                                 c91...
**UM82C493/491 ??????????????? [no datasheet]                        ?...
**UM8498/8496  486 VL Chipset  "Super Energy Star Green"[no dsheet]c94...
**UM8881/8886  HB4 PCI Chipset "Super Energy Star Green"[no dsheet]c94...
**UM8890       Pentium chipset [no datasheet]                        ?...
**
**Support Chips:
**UM82152      Cache Controller (AUStek A38152 clone)              <91...
**UM82C852     Multi I/O For XT                                    <91...
**UM82C206     Integrated Peripheral Controller                    <91...
**UM82c45x     Serial/Parallel chips                                 ?...
**Other chips:...
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