.\"	$OpenBSD: gsc.4,v 1.6 2002/04/07 10:14:31 mickey Exp $
.\"
.\"
.\" Copyright (c) 1999 Michael Shalayeff
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.Dd April 4, 1999
.Dt GSC 4
.Os
.Sh NAME
.Nm gsc
.Nd General System Connect bus on HP9000 series 700 workstations
.Sh SYNOPSIS
.Cd "gsc* at lasi?"
.Cd "gsc* at asp?"
.Cd "gsc* at wax?"
.Sh DESCRIPTION
This is core I/O bus for all HP9000/700 series workstations. All I/O subsystems
connect to this bus.
The devices can be either on seperate chips, expansion
cards or on an integrated megacell, like the LASI MBA.
.Pp
The
.Tn GSC
bus is a 32-bit wide, address and data multiplexed bus. In its "standard"
implementation it has a maximum throughput of 160MB/s, the "2x" implementation
reaches up to 250MB/s.
Some HPPA CPUs directly attach to this bus, namely the PA7100LC and PA7300LC.
.Pp
As for the expansion cards, there appeared different form-factors, depending on
bus-speed (standard or 2x) and specific models.
The standard formfactor is the "EISA form-factor", cards that look like
typical EISA cards with a different connector (100-pin female EBBL).
The Series 712 have their own special type
of GSC expansion cards, called the "GIO form-factor", which is quite small and
mostly has only one VLSI chip on it (in most cases LASI/WAX).
Newer systems sometimes feature the "HSC formfactor", that is a 1U-VME
card-like expansion card with a 100-pin male pin+socket connector.
Mixing cards with different speeds is supported but downgrades
the performance of the whole I/O-subsystem. 
.Pp
.Sh SUPPORTED DEVICES
The system includes machine-dependent
.Tn GSC
drivers, sorted by driver name:
.Bl -tag -width pcdisplay -offset indent
.It Xr com 4
RS-232 ports.
.It Xr hil 4
Human Interface Loop, for HP-proprietary input devices like keyboard and mice.
.It Xr ie 4
Intel i82C596 DX/CA 32-bit Ethernet interfaces.
.It Xr lpt 4
Centronics printer port.
.It Xr pckbc 4
PC-style keyboard controller.
.It Xr siop 4
NCR 53C700/710 narrow, single-ended or 53C720 wide,
differential SCSI I/O processor.
.El
.Pp
Some of these 
.Tn GSC
devices also have
.Tn PCI
,
.Tn EISA 
or
.Tn ISA 
equivalents.
These are listed in
.Xr pci 4 ,
.Xr eisa 4 ,
or
.Xr isa 4 ,
.Sh SEE ALSO
.Xr asp 4 ,
.Xr cpu 4 ,
.Xr intro 4 ,
.Xr lasi 4
.Sh HISTORY
The
.Nm
driver
appeared in
.Ox 2.4 .