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**A note on VESA support of 486 chipsets.
Many chipsets state  that they support VESA local  bus.  In some cases
these actually  implement VLB somewhat  like PCI, where it  is entirly
decoupled from the CPU bus. Chipsets  that do not state they work with
VLB,  may  be found  on  motherboards  that  contain VLB  slots.   VLB
is  *basically*  The 486  CPU  pinout in  a  slot  form. Unless  these
m/boards contain  some additional  chips, there VLB  implementation is
directly coupled to the CPU.

**Datasheets:...
*_IBM...
*ACC Micro...
*ALD...
*ALi...
*AMD . . . . . . . [no datasheets, some info]...
*Chips & Technologies...
*Contaq  . . . . . [no datasheets, some info]...
*Efar Microsystems [no datasheets, some info]...
*ETEQ...
*Faraday...
*Forex . . . . . . [List only, no datasheets found]...
*Intel...
**82396SX     Smart Cache                                     12/17/90
***Notes:...
***Info:...
***Versions:...
***Features:...
**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...
*HMC (Hulon Microelectronics)...
*Logicstar...
**SL6012  Memory Mapper for PC-AT (74LS612 compatible)          <Jul87
***Info:
The SL6012 Memory  Mapper is intended for use in  PC-AT design. It can
expand an address bus by 4  bits. In PC-AT applications, 4 bits of the
source  address   are  used  to  select   1  of  16,   eight  bit  map
registers. These registers  are normally programmed (through software)
with the  starting address of each  memory page. The  register data is
output directly for  use as the most significant  bits of the expanded
address bus. The 8 bits from the SL6012 are used along with the unused
source address bits to form the expanded address bus.

As shown  in Table 1  [see datasheet], the  SL6012 has three  modes of
operation; read, write and map. Data may be written into, or read from
the Memory  Mapper when  chip select CSN  is low. The  register select
inputs (RS0 through RS3) select one of the sixteen map registers. When
RWN is  low, data is written  into a register from  the data bus. When
RWN is high  data is output from a Memory Mapper  register to the data
bus.

The map mode of operation is selected when chip select CSN is high. In
this mode, the  register data selected by the  map address inputs (MA0
through  MA3)  will be  available  on  the  map outputs  (MO0  through
MO7).  Note that  the map  registers are  addressed by  either  the RS
inputs or  the MA inputs depending  upon the operating  mode. When MEN
(Map Enable) is low the map  outputs (MO0-MO7) are active. When MEN is
high, the map outputs are at high impedance.

***Versions:...
***Features:...
**SL9010  System Controller (80286/80386SX/DX, 16/20/25MHz)     <oct88...
**SL9020  Data Controller                                       <oct88...
**SL9025  Address Controller                                    <oct88...
**SL9090  Universal PC/AT Clock Chip                            <oct88
***Info:...
***Versions:...
***Features:...
**SL9250  Page Mode Memory Controller (16/20MHz 8MB Max)        <oct88...
**SL9350  Page Mode Memory Controller (16/20/25MHz 16MB Max)    <oct88...
**Other:...
*Motorola...
*OPTi...
*PC CHIPS/Amptron/Atrend/ECS/Elpina/etc...
*SIS...
*Symphony...
*TI (Texas Instruments)...
*UMC...
*Unresearched:...
*VIA...
*VLSI...
*Western Digital...
*Winbond...
*ZyMOS...
*General Sources:...