SCSI Chip Doubles Disk I/O Performance

Patent-Pending Chip Increases Speed of Computers and Servers

SAN JOSE, Calif., June 13, 1994 -- AdvanSys today announced a single-chip
Small Computer System Interface (SCSI) controller that is used by system
manufacturers to design SCSI connections in computers, workstations and
file servers.

The new chip increases the performance of these systems by doubling the
effective transfer rate of disk drives and other peripherals. The chip
also makes these systems easier to use by providing a single plug-and-play
SCSI connector that attaches up to seven different peripherals.

The new chip has twice the speed of competing SCSI devices because it uses
a patent-pending architecture that allows it to process up to 255
simultaneous data requests in an attached local memory. The other chips on
the market are slower because they must use a computer's memory when
processing more than four requests at a time.

The speed of the new AdvanSys chip is important for handling the tremendous
demands that operating systems now pul on SCSI controllers. For instance,
in a fraction of a second, a multitasking operating system, such as
Chicago, running several programs simultaneously, could issue hundreds of
requests for data. Or. in a fraction of a second, a multiuser operating
system, such as NetWare, could issue hundreds of requests for its users.

The new AdvanSys chip is available in two versions: The ASC1000 has a
32-bit VESA (Video Electronics Standards Association) local bus interface,
and the ASC1200, has a 32-bit PCI (Peripheral Component Interface) local
bus interface. These two versions allow an engineer to connect the chip to
either of the two local bus interfaces being used today.

According to Lou Williams, vice president of marketing, "The power of new
microprocessors, such as the 486, PowerPC and Pentium, has far outstripped
the ability of disk drives and other peripherals to deliver data for
processing. Our new chip helps solve this problem because it uses a new
multitasking architecture that can service the requests generated by these
processors and maintain a steady flow of data to them."

New Technology Boosts Speed

The new chip is a fifth-generation SCSI controller that contains an
advanced 32-bit RISC processor that operates at 10 MIPs (Million
Instructions Per Second). The chip also has three I/O ports (local bus
interface, local memory, and SCSI-2 interface), complete bytewide SCSI-2
hand-shake logic, a high-speed DMA (Direct Memory Access) circuit and a
128 byte FIFO memory.

The new chip is twice as fast as competing devices because it uses
patent-pending technology that allows it to process up to 255 simultaneous
data requests in an attached local memory. The RISC processor uses the
chip's memory port to log each request into a local memory, and then sends
the request to the appropriate peripheral.

Existing chips are slower because they log their request into one of four
on-chip registers. This four register approach slows down when more than
four requests are received because the operating system must wait as the
chip stores the new requests into the host computer's memory, which is
known as a mail box. It is unlikely that the register approach can be
improved because adding more registers will greatly increase the cost of a
chip.

The RISC processor in the AdvanSys chip also improves speed because it runs
scatter gather algorithms that store data together on a disk drive so that
it can be read back at the fastest possible rate.

The DMA portion of the new chip can provide automatic sustained transfers
at the 120 Mbyte/second rate of the VL and PCI interfaces. By eliminating
the need for the host CPU (Central Processing Unit) to participate in data
transfers, the DMA frees the CPU to do more data processing. The 128 byte
FIFO in the chip acts as a safety net to catch or buffer data coming in
from the 120 Mbyte/second local bus port.

New Architecture Lowers Chip Costs

Because the AdvanSys chip is built with one third the number of gates of
competing SCSI controllers, the new chip will be less expensive to build
in the long run. The AdvanSys chip achieved this reduction in gates by
using local memory to store the status of data requests instead of
internal registers. The new chip also uses fewer gates because its RISC
processor is fast enough to replace many of the conventional handshaking
circuits with compact microcode.

Making SCSI a Standard Feature in Computers

As a result of the lower chip cost that is possible with the AdvanSys
device, SCSI connections will begin to replace the IDE (Integrated Drive
Electronics) interface as the method of connecting peripherals to personal
computers.

SCSI's performance advantage will also help it replace IDE connections.
SCSI has an advantage because it can issue multiple requests to its disk
drives and keep them all busy searching for and transferring data to a
computer's processor. IDE cannot provide this type of speed up because it
can only request that one disk search at a time. IDE also slows a system
because it requires that the microprocessor sit idle while a disk is
searching for data.

SCSI also has the advantage that it can connect to a wider variety of
peripherals. For instance, while IDE only connects disk drives and CD-ROM
peripherals, the SCSI interface can connect tape drives, scanners, CD-ROM
jukeboxes, printers, etc. SCSI has the Flexibility to attach to new types
of peripherals that haven't even been conceived of yet.

The nine-foot reach of the SCSI cable has the advantage that it enables the
use of an external connector on the back of a computer which makes it easy
to plug in new peripherals. IDE, however, only reaches 1.5 feet, and with
no external connector, it forces a user to open their computer chassis to
add peripherals.

Availability and Price

The ASC1000 is in full production now and it is priced at $21.95 in 1,000
piece quantities. The chip is sold in a 160-pin PQFP (Plastic Quad Flat
Package).

The ASC1200 will sample in July and will be in full production in
September. It is also priced at $21.95 in 1,000 piece quantities. The chip
will be sold in a 160-pin PQFP (Plastic Quad Flat Package).

Reader Contact

Literature Department, AdvanSys, 1150 Ringwood Court, San Jose, CA, 95131.
Telephone: (408) 383-9400.

Company Background

AdvanSys is a Silicon Valley based company that designs and markets host
adapters, software and chips that increase the performance of personal
computers, workstations and network file servers. The company's products
improve the performance of these systems by boosting the speed at which
disk drives and other peripherals transfer data over the Small Computer
System Interface (SCSI).

The company sells its products, such as host adapters and software, to
computer resellers, distributors, value added resellers (VARs), value
added dealers (VADs), system integrators, system administrators, MIS
managers and original equipment manufacturers (OEMs). AdvanSys sells its
chips to computer manufacturers that design SCSI capability onto their
motherboards as a standard feature. AdvanSys is headquartered in San Jose,
Calif.

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