Texas Microsystems, Inc. 2003 - Option Compatibility

figuration has a capacity of 16M bytes of address space
that is 16 bits wide.
The 2000 Series XT configuration has ten 8-bit expan-
sion slots. Each slot has a 62 pin connector that pro-
vides 8 data bits and 20 address lines.
The AT 16-bit expansion cards are slightly (0.6 inches)
taller than the XT 8-bit expansion cards. To provide
for a hold down clamp that can accommodate the
different height boards, the AT cards are grouped
together near the center of the expansion slots
2.3.5 Option Compatibility
Modular options are added by means of expansion cards
that plug into the computer bus (expansion slots).
This bus is designed to be both electrically and
mechanically compatible with the equivalent
International Business Machine computer models.
On the 2000 Series AT (6MHz clock speed) and XT models,
the bus timing is identical to the IBM equivalent. The
AT computers, operating at 8 or 10 MHz, have faster bus
transfer rates and may not be compatible with all
expansion cards.
Although XT 8-bit expansion cards may work
electronically in the AT 16-bit slots, the XT cards may
not be physically compatible because the AT has the
additional 36 pin connector. In addition, the AT 16-
bit cards are not designed to work in 8-bit slots.
Expansion card compatibility may also vary, depending
on the manufacturer.
Processor clock speed differences may also effect
expansion card compatibility. The 2000 Series, AT,
80286 processor operates at a much faster speed (6, 8,
or 10 MHz) than the XT model 8088 processor speed (4.77
MHz). To accommodate this speed difference, the B286
card contains a programmable wait state generator which
inserts additional time in the bus transfer cycles.
Refer to the module section for a detailed description
of this feature. For most plug in modules, the
additional wait states are all that is required for
compatibility. If a speed problem is suspected,
contact the manufacturer of the plug in circuit card
regarding operation at the higher bus speeds.
Preliminary AT Users Manual
7
11/26/86