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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...
**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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*Unresearched:...
*VIA...
**VT82C597/AT  Apollo VP3, Single-Chip for Pentium with AGP  <10/03/97
***Info:...
***Configurations:...
***Features:
o   PCI/ISA Green PC Ready
    - Supports separately powered 3.3V (5V tolerant) interfaces to 
      system memory, AGP, and PCI bus
    - Supports 3.3V and sub-3.3V interface to CPU
    - PC-97 compatible using VT82C586B South Bridge with ACPI Power 
      Management
o   High Integration
    - Single chip implementation for 64-bit Socket-7-CPU, 64-bit 
      system memory, 32-bit PCI and 32-bit AGP interfaces
    - Apollo VP3  Chipset: VT82C597 or VT82C597AT  system controller 
      and VT82C586B  PCI to ISA bridge
    - Chipset includes UltraDMA-33 EIDE, USB, and Keyboard / PS2-Mouse 
      Interfaces plus RTC / CMOS on chip
o   Flexible CPU Interface
    - Supports 64-bit Pentium, AMD 5k86, AMD 6k86 and Cyrix 6x86 CPUs
    - CPU external bus speed up to 66 MHz (internal 233MHz and above)
    - Supports CPU internal write-back cache
    - System management interrupt, memory remap and STPCLK mechanism
    - Cyrix 6x86 linear burst support
    - CPU NA# / Address pipeline capability
    - 4 cache lines of CPU/cache-to-DRAM post-write buffers
    - 4 quadwords of CPU/cache-to-DRAM read-prefetch buffers
o   Advanced Cache Controller
    - Direct map write back or write through secondary cache
    - Pipelined burst synchronous SRAM (PBSRAM) cache support (with 
      global write enable feature)
    - Flexible cache size: 0K / 256K / 512K / 1M / 2MB
    - 32 byte line size to match the primary cache
    - Integrated 10-bit tag comparator
    - 3-1-1-1 read/write timing for PBSRAM access at 66 MHz
    - 3-1-1-1-1-1-1-1 back to back read timing for PBSRAM access at 
      66 MHz
    - Sustained 3 cycle write access for PBSRAM access or CPU to DRAM 
      and PCI bus post write buffers at 66 MHz
    - Data streaming for simultaneous primary and secondary cache line 
      fill
    - System and video BIOS cacheable and write-protect
    - Programmable cacheable region and cache timing
o   AGP Controller
    - AGP v1.0 compliant
    - Supports SideBand Addressing (SBA) mode (non-multiplexed 
      address/data)
    - Supports 133MHz 2X mode for AD and SBA signalling
    - Pipelined split-transaction long-burst transfers up to 533 MB/
      sec
    - Eight level read request queue
    - Four level posted-write request queue
    - Thirty-two level (quadwords) read data FIFO (128 bytes)
    - Sixteen level (quadwords) write data FIFO (64 bytes)
    - Intelligent request reordering for maximum AGP bus utilization
    - Supports Flush/Fence commands
o   GART
    - One level TLB structure
    - Sixteen entry fully associative page table
    - LRU replacement scheme
    - Independent GART lookup control for host / AGP / PCI master 
      accesses
o   Intelligent PCI Bus Controller
    - PCI buses are synchronous to host CPU bus
    - 33 MHz operation on the primary PCI bus
    - 66 MHz PCI operation on the AGP bus
    - PCI-to-PCI bridge configuration on the 66MHz PCI bus
    - Separate data buffers for the two PCI buses
    - Peer concurrency
    - Concurrent multiple PCI master transactions;  i.e., allow PCI 
      masters from both PCI buses active at the same time
    - Allows PCI master access while ISA master/DMA is active
    - PCI master snoop ahead and snoop filtering
    - Five levels (double-words) of CPU to PCI posted write buffers
    - Byte merging in the write buffers to reduce the number of PCI 
      cycles and to create further PCI bursting possibilities
    - Zero wait state PCI master and slave burst transfer rate
    - PCI to system memory data streaming up to 132Mbyte/sec
    - Enhanced PCI command optimization (MRL, MRM, MWI, etc.)
    - Forty-eight levels (double-words) of post write buffers from PCI 
      masters to DRAM
    - Sixteen levels (double-words) of prefetch buffers from DRAM for 
      access by PCI masters
    - Supports L1/L2 write-back forward to PCI master read to minimize 
      PCI read latency
    - Supports L1/L2 write-back merged with PCI master post-write to 
      minimize DRAM utilization
    - Transaction timer for fair arbitration between PCI masters 
      (granularity of two PCI clocks)
    - Symmetric arbitration between Host/PCI bus for optimized system 
      performance
    - Complete steerable PCI interrupts
    - PCI-2.1 compliant, 32 bit 3.3V PCI interface with 5V tolerant 
      inputs
o   Advanced High-Performance DRAM Controller
    - 66MHz DRAM interface
    - Concurrent CPU and AGP access
    - FP, EDO, SDRAM, and SDRAM-II
    - 66MHz DDR (Double Data Rate) supported for SDRAM-II
      (supports central and edge DQ, bidirectional DS, and optional 
      SDR write)
    - Different DRAM types may be used in mixed combinations
    - Different DRAM timing for each bank
    - Mixed 1M / 2M / 4M / 8M / 16MxN DRAMs
    - 6 banks up to 1GB DRAMs
    - Flexible row and column addresses
    - 64-bit data width only
    - 3.3V DRAM interface with 5V-tolerant inputs
    - Optional bank-by-bank ECC (single-bit error correction and 
      multi-bit error detection) or EC (error checking only) for DRAM 
      integrity
    - Two-bank interleaving for 16Mbit SDRAM support
    - Two-bank and four bank interleaving for 64Mbit SDRAM support 
      (14 MA lines)
    - Supports maximum 8-bank interleave (i.e., 8 pages open 
      simultaneously);  banks are allocated based on LRU
    - Seamless DRAM command scheduling for maximum DRAM bus utilization
      (e.g., precharge other banks while accessing the current bank)
    - Four cache lines (16 quadwords) of CPU/cache to DRAM write 
      buffers
    - Concurrent DRAM writeback
    - Read around write capability for non-stalled CPU read
    - Burst read and write operation
    - 5-2-2-2 on page, 8-2-2-2 start page and 11-2-2-2 off page timing 
      for EDO DRAMs at 66 MHz
    - 6-1-1-1 on page, 8-1-1-1 start page and 10-1-1-1 off page for 
      SDRAMs at 66 MHz
    - 5-2-2-2-3-2-2-2 back-to-back accesses for EDO DRAM at 66 MHz
    - 6-1-1-1-3-1-1-1 back-to-back accesses for SDRAM at 66 MHz
    - BIOS shadow at 16KB increment
    - Decoupled and burst DRAM refresh with staggered RAS timing
    - Programmable refresh rate, CAS-before-RAS refresh and refresh on 
      populated banks only
o   Built-in NAND-tree pin scan test capability
o   3.3V, 0.5um, high speed / low power CMOS process
o   472 pin BGA Package
o   Alternate pinouts available to optimally accommodate different PCB 
    form factors
    - VT82C597 for ATX and NLX
    - VT82C597AT for Baby AT and ATX

**VT82C598MVP  Apollo MVP3,Single-Chip 66/75/83/100MHz & AGP <09/22/97...
**VT8501       Apollo MVP4,Single-Chip 66-100MHz & AGP       <11/04/98...
**VT82C680     Apollo P6, Pentium-Pro Chip Set               <08/30/96...
**Support chips:
**VT82C505     Pentium/486 VL to PCI Bridge                  <05/30/94...
**VT82C586/A/B PCI Integrated Peripheral Controller          <10/13/96...
**VT82C596/A   Mobile PCI Integrated Peripheral Controller   <11/05/97...
**VT82C686A/B  PCI Super-I/O Integrated Peripheral Ctrl.     <02/10/98...
**Later P-Pro/II/III/Celeron...
**Later AMD...
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