text:
Louis Jolliet

Louis Jolliet (September 21, 1645 – after May 1700) was a French-Canadian explorer known for his discoveries in North America. In 1673, Jolliet and Jacques Marquette, a Jesuit Catholic priest and missionary, were the first non-Natives to explore and map the Upper Mississippi River.

Early life
Jolliet was born in 1645 in Beaupré, a French settlement near Quebec City, to Jean Jolliet and Marie D'Abancourt. When he was six years old, his father died; his mother married a successful merchant, Geoffroy Guillot dit Lavalle, until he died in 1665. Shortly after the passing of his mother's second husband, she was married to Martin Prevost until she died in 1678. Jolliet's stepfather owned land on the Ile d'Orleans, an island in the Saint Lawrence River in Quebec that was home to First Nations. Jolliet spent much time on Ile d'Orleans, so he likely began speaking Indigenous languages of the Americas at a young age. Besides French, he also learned English and Spanish. During his childhood, Quebec was the center of the French fur trade. The Natives were part of daily life in Quebec, and Jolliet grew up knowing much about them. Jolliet entered a Jesuit school in Quebec as a child and focused on philosophical and religious studies, aiming for the priesthood. He also studied music, becoming a skilled harpsichordist and church organist. He received Holy Orders in 1662 but abandoned his plans to become a priest, leaving the seminary in 1667 to pursue fur trading instead.

Exploration of the Upper Mississippi

While Hernando de Soto was the first European to make official note of the Mississippi River by discovering its southern entrance in 1541, Jolliet and Marquette were the first to locate its upper reaches, and travel most of its length, about 130 years later. De Soto had named the river Rio del Espiritu Santo, but tribes along its length called it variations of "Mississippi", meaning "Great River" in the Algonquian languages.

On May 17, 1673, Jolliet and Marquette departed from St. Ignace, Michigan, with two canoes and five other voyageurs of French-Indian ancestry. The group sailed to Green Bay. They then paddled upstream (southward) on the Fox River to the site now known as Portage, Wisconsin. There, they portaged a distance of slightly less than two miles through marsh and oak forest to the Wisconsin River. Europeans eventually built a trading post at that shortest convenient portage between the Great Lakes and Mississippi River basins. On June 17, the canoeists ventured onto the Mississippi River near present-day Prairie du Chien, Wisconsin.

The Jolliet-Marquette expedition paddled along the west bank of the Mississippi until mid-July. When they passed the mouth of the Arkansas River, they became satisfied that they had established that the Mississippi flowed into the Gulf of Mexico. By this point, they had encountered natives carrying European goods and worried about a possible hostile encounter with explorers or colonists from Spain. The voyageurs then followed the Mississippi back to the mouth of the Illinois River, which friendly natives told them was a shorter route back to the Great Lakes. Following the Illinois river upstream, they then turned up its tributary the Des Plaines River near modern-day Joliet, Illinois. They then continued up the Des Plaines River and portaged their canoes and gear at the Chicago Portage. They then followed the Chicago River downstream until they reached Lake Michigan near the location of modern-day Chicago. Father Marquette stayed at the mission of St. Francis Xavier at the southern end of Green Bay, which they reached in August. Jolliet returned to Quebec to relate the news of their discoveries. On his way through the Lachine Rapids, Jolliet's canoe overturned and his records were lost. His brief narrative, written from memory, is in essential agreement with Marquette's, the chief account of the journey.

Later years
Jolliet married Claire-Françoise Byssot de la Valtrie. Like Jolliet, she was Canadian born, a daughter of Francois Byssot de la Riviere and his wife Marie Couillard. Claire Francoise was also a sister of Louise Byssot de la Valtrie, wife of Seraphin de Margane, Seigneur de la Valtrie. In 1680, Jolliet was granted the Island of Antwhere by Louis XIV as a reward, where he created a fort and maintained soldiers. In 1693, he was appointed "Royal Hydrographer", and on April 30, 1697, he was granted a seigneury southwest of Quebec City which he named Jolliest.

In 1694, he sailed from the Gulf of St. Lawrence north along the coast of Labrador as far north as Zoar, a voyage of five and a half months. He recorded details of the country, navigation, the Inuit and their customs. His journal ("Journal de Louis Jolliet allant à la decouverte de Labrador, 1694,") is the earliest known detailed survey of the Labrador coast from the Strait of Belle Isle to Zoar.

In May 1700, Louis Jolliet left for Anticosti Island. He then disappears from the historical record. There is no listing of his death or burial place, and the sole record of his fate is the notation that a mass for his soul was said in Quebec on September 15, 1700.

Legacy
Jolliet's main legacy is most tangible in the Midwestern United States and Quebec, mostly through geographical names, including the cities of Joliet, Illinois; Joliet, Montana; and Joliette, Quebec (founded by one of Jolliet's descendants, Barthélemy Joliette).

The several variations in the spelling of the name "Jolliet" reflect spelling that occurred at times when illiteracy or poor literacy was common and spelling was unstandardized. Jolliet's descendants live throughout eastern Canada and the United States.

The Jolliet Squadron of cadets at the Royal Military College Saint-Jean in the Province of Quebec was named in Jolliet's honor. A street and subway station in Montreal, Quebec are named after him. The Louis Jolliet rose, developed by Agriculture and Agri-Food Canada, was named in his honor. Joliet Junior College in Joliet, Illinois, is named after the explorer, as are numerous high schools in North America. The Louis Joliet Mall in Joliet, Illinois, is named for the explorer. A cruise ship sailing out of Quebec City is also named in his honour.

Jolliet appears with Jacques Marquette on a 1968 United States postage stamp honoring their exploratory voyage.

title: Louis Jolliet


text:
ST506/ST412

The ST-506 and ST-412 (sometimes written ST506 and ST412 ) were early hard disk drive products introduced by Seagate in 1980 and 1981 respectively, that later became construed as hard disk drive interfaces: the ST-506 disk interface and the ST-412 disk interface. Compared to the ST-506 precursor, the ST-412 implemented a refinement to the seek speed, and increased the drive capacity from 5 MB to 10 MB, but was otherwise highly similar.

Beginning with its selection as the hard drive subsystem for the original IBM XT disk drive controllers supporting the ST-412 interface grew to become ubiquitous in the personal computer industry, The ST-412 interface and its variants were the de facto industry standard for personal computer hard disks until the advent and wider adoption of the IDE or ATA interface in the early 1990s.

Both interfaces used MFM encoding; the subsequent extension of the ST-412 interface, the ST-412HP interface, used RLL encoding for a 50% increase in capacity and bit rate.

History
The ST506 HDD was the first 5.25 inch hard disk drive, introduced in 1980 by Shugart Technology (now Seagate Technology). It stored up to 5 megabytes after formatting (153 cylinders, 4 heads, 32 sectors/track, 256 bytes/sector) and cost US$1,500. The similar, 10-megabyte ST412 HDD was introduced in late 1981 (with 306 cylinders). The ST225 was introduced shortly thereafter with 20 megabytes and half the height. All three used MFM encoding, a widely used coding scheme. A subsequent extension of the ST412 interface, the ST412HP interface, used RLL encoding for a 50% increase in capacity and bit rate.

The ST506 drive connected to a computer system through a disk controller. The ST506 interface between the controller and drive was derived from the Shugart Associates SA1000 interface, which was in turn based upon the floppy disk drive interface, thereby making disk controller design relatively easy.

The ST412 interface was adopted by numerous HDD manufacturers such that the interface became a de facto industry standard for disk drives well into the 1990s.

The limitations of the ST412 interface are 5 million transitions per second maximum on data lines, 16 heads, 4 drive units and a 20 ft cable length. The standard channel code for the ST412 (and ST506) is MFM with one data bit per transition for a data rate of 5 Mbit/s. The ST412HP RLL variant averages 1.5 data bits per transition for a data rate of 7.5 Mbit/s.

Interface to controller

In the ST506 interface, the drive connects to a controller card with two ribbon cables carrying signals, while a third cable provides power. The two signal cables are the wide 34-pin control cable and the narrow 20-pin data cable. The control cable interface is very similar to the standard Shugart floppy disk interface; like that floppy disk interface, it can support four drives. The data cable carries a read signal and write signal, both as differential binary signals: the two signal states correspond to the two possible differential signal polarities. The data represented by these signals is MFM, so the absolute signal states are not significant: the data is represented in the timing of the state transitions, like in floppy disk systems. While up to four drives can share a control cable, each drive has its own dedicated data cable connecting it to the hard disk controller (HDC). Most HDCs supported only two drives.

The control card translates requests for a particular track and sector from the host system into a sequence of head positioning commands, including setting the direction of head movement, in or out, and sending individual "STEP" commands to move. Four of the control cable pins, "HD SLCT 0" through "HD SLCT 3", allow the selection among up to 16 heads, although only four are available on the two-platter ST506. The original ST506/ST412 interface defined only two HD SLCT lines, providing supporting for only four heads, but a third HD SLCT line was shortly added to the design; a fourth was added a not much later by redefining the reduced Write Current signal, needed only by very early drives, as HD SLCT 3. Once the heads are properly positioned and the appropriate head is selected, data is read or written serially through a set of pins in the data cable. The limited bandwidth of the data cable was not an issue at the time and is not the factor that limited the performance of the system. However, the unshielded cable can sometimes be susceptible to high levels of noise.

The ST412 disk drive, among other improvements, added buffered seek capability to the interface. In this mode, the controller can send STEP pulses to the drive as fast as it can receive them, without having to wait for the mechanism to settle. An onboard microprocessor in the drive then moves the mechanism to the desired track as fast as possible. The ST506 disk drive without buffered seek averages 170 ms (similar to a floppy drive or modern optical drive) while the mechanically very similar ST412 disk drive with buffered seek averages 85 ms. By the late 1980s, drives with an ST412 interface were capable of average seek times between 15 and 30 milliseconds.

The process of moving portions of the command interpretation off the controller card and onto the drive itself in order to improve performance is a common feature of later hard drive connection schemes, notably SCSI, with its rich command set, and the storage-focused IDE systems. IDE, in effect, is a system for extending the computer bus so the interface controller can be built into the drive unit rather than being plugged into the computer's backplane. This allows a single "controller" card—really just an interface card—to communicate with multiple dissimilar drives, while it also reduces latency and noise between the controller and drive hardware. Effectively, the roles are reversed: instead of the controller doing almost all of the complex processing and the drive just transferring encoded data between the magnetic disks and the controller, the drive does almost all of the complex processing and the "controller" just transfers decoded data between the drive and the host system. In these systems, the operational details of the drive, like head selection and seeking, are entirely hidden from the host and handled within the drive's dedicated controller. These became known as "smart" drives, while ST506-like devices retroactively became known as "dumb".

While integrated controllers have many benefits, they also have a disadvantage: the mechanical drive (called the "head-disk assembly", or HDA) and the controller are effectively fused into a monolithic black box, so that if something goes wrong with the drive, it is nearly impossible to do anything about it—the data is usually irretrievably lost. With a separated controller and disk system like that of the ST506 interface, sometimes the problem can be resolved by connecting the disk drive, containing the actual (perhaps very important) data, to another compatible controller. Furthermore, an ST506 style interface makes it possible and easy not only to replace the controller without throwing away the data, but to get access to the analog data signals from the disk drive and process them through a special data recovery system that may be able to reconstruct data that a normal controller cannot read. Such data recovery techniques are much more difficult to execute on integrated drives, because the needed analog signals from the disk are not available at a standard interface and the internal data recording method, sector format, and disk organization of nearly every integrated drive model is different and secret.

Compatible systems and developments
Many other companies quickly introduced drives using the same connectors and signals, creating a hard drive standard based on the ST506. IBM chose to use it, acquiring adapter cards for the PC/XT from Xebec and for the PC/AT from Western Digital. As a consequence of IBM's endorsement, most of the drives in the 1980s were based on the ST506. However, the complexity of the controller and cabling led to newer solutions like SCSI, and later, ATA (IDE). A few early SCSI drives were actually ST506 drives with a SCSI to ST506 controller on the bottom of the drive. Atari also used Adaptec ACB-4000A SCSI to ST506 converter inside its own line of SH204/SH205 external ACSI drives. Likewise a few early IDE drives were just drives with an ST412 interface attached to a controller board or chip. Ultimately all SCSI and ATA drives had built the controller into the drive, thereby eliminating the ST506/412 interface in such models.

Connector pinouts
From ST506/ST412 OEM manual. In the following tables, "~" denotes a negated (active low) signal.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: ST506/ST412