Browse Prior Art Database

32-Bit Memory Subsystem Supports Intel 80386 And 80386SX Processors

IP.com Disclosure Number: IPCOM000101603D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Szarek, JJ: AUTHOR [+2]

Abstract

This article describes a single planar design with 32-bit memory subsystem which will accommodate both Intel 80386 and 80386SX processors.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 72% of the total text.

32-Bit Memory Subsystem Supports Intel 80386 And 80386SX Processors

       This article describes a single planar design with 32-bit
memory subsystem which will accommodate both Intel 80386 and 80386SX
processors.

      Referring to the figures, Fig. 1 is a functional block diagram
of the planar design for the 80386 and Fig. 2 is a functional block
diagram of the planar design for the 80386SX.

      Since the 80386 provides -BE(3:0) for selection of up to 4
bytes wide, the 80386SX provides A0, A1, and -BHE for selection of up
to two bytes wide.  The CPU support chip which is a NEC BiCMOS
converts A0, A1, and -BHE to -CBE(3:0) and multiplexes with the 80386
-BE(3:0) and feeds the multiplexed output -ASBE(3:0) to the memory
controller chip. The CPU support chip selects -CBE(3:0) or -BE(3:0)
depending upon which processor is installed.  The detection technique
for the processor installed is described in the reference.

      The planar in this system provides a 150-pin grid array (PGA)
socket instead of the usual 132 PGA socket to accommodate the
additional 80386SX low address signals A0, A1, -BHE.  An 80386 can be
plugged directly into this socket, but with the 80386SX, an adapter
card is used to mount the 80386SX with the data bus D(16:31)
connected together with the corresponding D(15:0) (D0 to D16, D1 to
D17...).

      In the 80386SX processor environment, the planar memory becomes
16 bits wide because of the connection between the low word and t...