Electrical computers and digital data processing systems: input/ – Input/output data processing – Peripheral adapting
Reexamination Certificate
1998-05-27
2001-01-09
Coleman, Eric (Department: 2783)
Electrical computers and digital data processing systems: input/
Input/output data processing
Peripheral adapting
C710S063000, C711S167000
Reexamination Certificate
active
06173344
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to computer adapter cards, and more particularly to computer adapter cards that are capable of interconnecting data buses having target peripheral devices to a host computer system.
2. Description of the Related Art
As the power of applications, processors, and storage devices increase, high-end computer users are seeking ways to optimize their computer systems to achieve the highest level of performance. For example, most of today's computer systems are highly modular systems that enable them to be modified and equipped with just the right software and hardware. Typically, a computer's mother board includes several peripheral component interconnect (PCI) slots that are configured to receive adapter cards, such as SCSI adapter cards. These SCSI adapter cards act as a reliable and efficient interface between the host computer and any number of peripheral devices. In general, once a SCSI adapter card is inserted into the host computer's PCI slot, a SCSI bus (typically in the form of a ribbon cable) is used to interconnect one or more peripheral devices (also known as target devices) to the SCSI host adapter.
In recent years, there have been many improvements to the SCSI bus technology which has lead to the development of several different types of SCSI buses, each having their own performance characteristics. For ease of discussion,
FIG. 1A
is an example of an Ultra bus system
100
, which is in the form of a cable
102
that includes several connectors
104
. The Ultra bus system
100
typically has seven (7) connectors
104
which are 50 pin connectors, and the cable
102
is capable of communicating data at speeds up to about 20 Megabytes/second, for 8-bit devices. Alternatively, if the cable
102
is an Ultra Wide bus, the Ultra bus system
100
will be capable of communicating data at speeds up to about 40 Megabytes/second, for 16-bit devices. Also, Ultra Wide buses typically have fifteen (15) connectors
104
having 68 pins. Accordingly, the Ultra bus system
100
is capable of interconnecting either up to 7 or up to 15 target devices
106
, in a parallel arrangement, to the SCSI host adapter. Thus, depending on whether the Ultra bus system
100
has an Ultra or Ultra Wide bus, it will be capable of supporting data transfer rates up to 20 or 40 Megabytes/second.
FIG. 1B
illustrates an Ultra2 bus system
120
having a low voltage differential (LVD) cable
122
and respective 68 pin connectors
124
. In general, the LVD cable
122
of the Ultra2 bus system
120
is known to be a lower power consuming system than the Ultra bus system
100
, and provides the ability to drive cable lengths up to 12 meters or more. This is substantial when compared to the Ultra bus system
100
, which can only typically drive cable lengths of about 3 meters. Most significantly, the Ultra2 bus system
120
is capable of running at data transmission speeds up to about 80 Megabytes/second, for 16-bit Ultra2 devices. As can be appreciated, higher performance systems will typically want to take advantage of the high data transmission speeds by incorporating Ultra2 bus systems
120
into there computer system. To fully take advantage of the increased data transmission speeds offered by the Ultra2 bus system
120
, Ultra2 target devices
126
should be connected to the connectors
124
. Unfortunately, when older Ultra target devices
106
are connected to the Ultra2 bus system
120
, the transmission speeds for all other devices on the bus, including the Ultra2 target device
126
, will suffer a substantial reduction in speed, which is typically about half or more.
For example, assume that the Ultra2 target device
126
was enjoying a transmission rate of about 80 Megabytes/second along the Ultra2 bus system
120
before the Ultra target device
106
was connected to the bus. After the Ultra target device
106
is connected to the bus, the transmission rate for all target devices (Ultra2 and non-Ultra2 devices) connected to the bus will not be more than the transmission rate of the Ultra target device
106
. Therefore, if the Ultra target device
106
is an Ultra Wide device that is capable of running at 40 Megabytes/second, then the fastest the Ultra2 target device
126
can run is 40 Megabytes/second. This is true even though both the LVD cable
122
and the Ultra2 target device
126
is capable of running at speeds up to about 80 Megabytes/second.
Accordingly, if a user desires to install an LVD cable
122
to interconnect the SCSI host adapter to peripheral devices, such as, hard drives, CD-ROMs, DVD drives, tape drives, and the like, the user will also have to replace all non-Ultra2 peripheral devices to take advantage of the higher speeds offered by an Ultra2 bus system. As can be appreciated, the replacement of all peripheral devices can be a costly solution, considering that only selected speed sensitive peripheral devices need to run at the Ultra2 speeds. Furthermore, being that SCSI Ultra bus is a more established technology, there is a greater likelihood that a majority of the peripheral devices that are currently installed in existing computer systems will be Ultra target devices. As such, many users that desire the improved data transmission speeds of Ultra2 target devices will decide not to install an Ultra2 bus and an Ultra2 peripheral device because, if older Ultra target devices are connected to the Ultra2 bus, the faster transmission rates of the SCSI Ultra2 will not be realized.
In view of the foregoing, there is a need for a SCSI technology adapter that enables use of both Ultra and Ultra2 target devices without reducing the data transmission rates of the faster Ultra2 target devices.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing a SCSI host adapter that is capable of coupling to both a SCSI Ultra2 bus and a SCSI Ultra bus, and is capable of maintaining higher performance levels of Ultra2 target devices even when Ultra target devices are connected to the same SCSI host adapter. Also disclosed are method for making a SCSI host adapter having a transceiver unit for enabling operation of both SCSI Ultra2 and SCSI Ultra target devices, without negatively impacting on the high performance characteristics of SCSI Ultra2 devices. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, a method, or a computer readable medium. Several inventive embodiments of the present invention are described below.
In one embodiment, a SCSI host adapter is disclosed. The SCSI host adapter includes a first connector for connecting the SCSI host adapter to a first bus, and a second connector for connecting the SCSI host adapter to a second bus. The SCSI host adapter also includes a transceiver unit that is in communication between the first bus and the second bus. The transceiver unit is configured to electrically isolate the first bus from the second bus so as to enable a maximum burst rate for target devices that are connected to each of the first bus and the second bus. In this embodiment, the transceiver unit is configured to produce a target information signal that identifies whether a data transfer operation is being executed between the first bus and the SCSI host adapter or between the second bus and the SCSI host adapter.
In another embodiment, a host adapter for use in a computer system is disclosed. The host adapter is configured to provide the computer system with interconnection with internal and external target devices. The host adapter includes a low voltage differential connector for interconnecting to a low voltage differential bus, and the low voltage differential bus is configured to communicate a first transaction. The host adapter also includes a single ended connector for interconnecting to a single ended bus, and the single ended bus is configured to communicate a second transaction. Furthermore, the host adapter includes a transceiver unit t
Burns Christopher
Cheung Peter K.
Davis Barry
Mohammed Abdul Waheed
Adaptec, Inc
Coleman Eric
Martine Penilla & Kim LLP
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