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SYM53C875/875E Data Manual
Introduction
Package and Feature Options
memory is pictured in Figure 1-1. A block diagram
of the SYM53C875 is pictured in Figure 1-2 on
page 1-6.
T he SYM53C875 integrates a high-performance
SCSI core, a PCI bus master DMA core, and the
Symbios SCSI SCRIPT S processor to meet the
flexibility requirements of SCSI-3 and Ultra SCSI
standards. It is designed to implement multi-
threaded I/O algorithms with a minimum of pro-
cessor intervention, solving the protocol overhead
problems of previous intelligent and non-intelli-
gent adapter designs.
T he SYM53C875 is fully supported by the
Symbios SCSI Device Management System
(SDMS ), a software package that supports the
Advanced SCSI Protocol Interface (ASPI) and the
ANSI Common Access Method (CAM). SDMS
provides BIOS and driver support for hard disk,
tape, removable media products, and CD-ROM
under the major PC operating systems.
Package and Feature
Options
T he SYM53C875 is available in three versions
with different packaging and feature options. T he
SYM53C875 is packaged in a 160-pin plastic quad
flat pack. T he SYM53C875J is identical to the
SYM53C875 with additional pins that support
JTAG boundary scan testing. T he JTAG boundary
scan signals replace the T EST IN, MAC/
_T EST OUT, BIG_LIT /, and SDIRP1 pins. T he
SYM53C875N includes all of the signals in the
SYM53C875, with the additions of the JTAG pins
and four additional signals for extended parity
checking and generation. It is packaged in a 208-
pin plastic quad flat pack.T he SYM53C875JB is
identical to the SYM53C875J, but is packaged in a
169-pin ball grid array. T he devices that have been
upgraded to include the power management fea-
tures are: SYM53C875E, SYM53C875JE, and
SYM53C875JBE.
Benefits of Ultra SCSI
Ultra SCSI is an extension of the SCSI-3 standard
that expands the bandwidth of the SCSI bus and
allows faster synchronous SCSI transfer rates.
When enabled, Ultra SCSI performs 20 mega-
transfers during an I/O operation, which results in
approximately doubling the synchronous transfer
rates of fast SCSI-2. T he SYM53C875 can per-
form 8-bit, Ultra SCSI synchronous transfers as
fast as 20 MB/s. T his advantage is most noticeable
in heavily loaded systems, or large-block size appli-
cations such as video on-demand and image pro-
cessing.
One advantage of Ultra SCSI is that it significantly
improves SCSI bandwidth while preserving exist-
ing hardware and software investments. T he
SYM53C875 is compatible with all existing
SYM53C825 and SYM53C825A software; the
only changes required are to enable the chip to
perform synchronous negotiations for Ultra SCSI
rates. T he SYM53C875 can use the same board
socket as an SYM53C825, with the addition of an
80MHz SCLK or enabling the internal SCSI clock
doubler to provide the correct frequency when
transferring synchronous SCSI data at 50 nanosec-
ond transfer rates. Some changes to existing
cabling or system designs may be needed to main-
tain signal integrity at Ultra SCSI synchronous
transfer rates. T hese design issues are discussed in
Chapter 2.