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Old 02-02-2008, 05:39 PM
William Case
 
Default Difference between IDE and SCSI ??

Hi;

Can someone briefly explain to me the difference between an IDE (ATA)
and a SCSI device. After having done due diligence with google searches
etc., I am still in a quandary. Nothing I read seems to be consistent.
Every time I think I have it figured out, I read a reference that calls
for or lists IDE devices that I think should be a SCSI reference and
vice versa. Even going to the various standards sites doesn't clarify
it for me. In fact it makes it more confusing.

Therefore, can someone explain, in plain language, how I should use the
terms IDE or PATA, and SCSI correctly with regards to a current
computer? What specific attribute of a device or bus does each term
apply to?

Given below are some questions that spring to mind. They may be
mis-formed questions and therefore need not be answered, but they may
demonstrate where my confusion and misunderstanding are coming into
play.

e.g.
Does IDE refer to the physical device?
Or, specifically just to the bus used?
Or, to the driver for the device?
Or, the type of interface (plug)?

Does SCSI refer to a set of protocols used when designing the device?
Or, to a specific driver design?

Can you have an IDE device without SCSI?
Or, can you have a SCSI device without it being IDE?

Below, I have listed a few of the sites I have visited with the
definitions given to show I have found the history and some attempts at
an explanation. I long ago learnt that any manual's reference to IDE or
SCSI usually simply meant some reference to my hard drive. I am aware
it could also mean my CD or a DVD, but usually it is a reference to a
HD.

http://en.wikipedia.org/wiki/IDE
http://en.wikipedia.org/wiki/Integrated_Drive_Electronics
http://en.wikipedia.org/wiki/SCSI


Integrated Drive Electronics, a computer hardware bus used primarily for
hard drives and optical drives (e.g. CD, DVD)

Advanced Technology Attachment (ATA) is a standard interface for
connecting storage devices such as hard disks and CD-ROM drives inside
personal computers.

The standard is maintained by X3/INCITS committee T13. Many synonyms and
near-synonyms for ATA exist, including abbreviations such as IDE and
ATAPI. Also, with the market introduction of Serial ATA in 2003, the
original ATA was retroactively renamed Parallel ATA (PATA).


SCSI (Small Computer System Interface) is a set of standards for
physically connecting and transferring data between computers and
peripheral devices. The SCSI standards define commands, protocols, and
electrical and optical interfaces. SCSI is most commonly used for hard
disks and tape drives, but it can connect a wide range of other devices,
including scanners and CD drives. The SCSI standard defines command sets
for specific peripheral device types; the presence of "unknown" as one
of these types means that in theory it can be used as an interface to
almost any device, but the standard is highly pragmatic and addressed
toward commercial requirements.
--
Regards Bill

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Old 02-02-2008, 06:57 PM
Les
 
Default Difference between IDE and SCSI ??

On Sat, 2008-02-02 at 13:39 -0500, William Case wrote:
> Hi;
>
> Can someone briefly explain to me the difference between an IDE (ATA)
> and a SCSI device. After having done due diligence with google searches
> etc., I am still in a quandary. Nothing I read seems to be consistent.
> Every time I think I have it figured out, I read a reference that calls
> for or lists IDE devices that I think should be a SCSI reference and
> vice versa. Even going to the various standards sites doesn't clarify
> it for me. In fact it makes it more confusing.
>
> Therefore, can someone explain, in plain language, how I should use the
> terms IDE or PATA, and SCSI correctly with regards to a current
> computer? What specific attribute of a device or bus does each term
> apply to?
>
> Given below are some questions that spring to mind. They may be
> mis-formed questions and therefore need not be answered, but they may
> demonstrate where my confusion and misunderstanding are coming into
> play.
>
> e.g.
> Does IDE refer to the physical device?
> Or, specifically just to the bus used?
> Or, to the driver for the device?
> Or, the type of interface (plug)?
>
> Does SCSI refer to a set of protocols used when designing the device?
> Or, to a specific driver design?
>
> Can you have an IDE device without SCSI?
> Or, can you have a SCSI device without it being IDE?
>
> Below, I have listed a few of the sites I have visited with the
> definitions given to show I have found the history and some attempts at
> an explanation. I long ago learnt that any manual's reference to IDE or
> SCSI usually simply meant some reference to my hard drive. I am aware
> it could also mean my CD or a DVD, but usually it is a reference to a
> HD.
>
> http://en.wikipedia.org/wiki/IDE
> http://en.wikipedia.org/wiki/Integrated_Drive_Electronics
> http://en.wikipedia.org/wiki/SCSI
>
>
> Integrated Drive Electronics, a computer hardware bus used primarily for
> hard drives and optical drives (e.g. CD, DVD)
>
> Advanced Technology Attachment (ATA) is a standard interface for
> connecting storage devices such as hard disks and CD-ROM drives inside
> personal computers.
>
> The standard is maintained by X3/INCITS committee T13. Many synonyms and
> near-synonyms for ATA exist, including abbreviations such as IDE and
> ATAPI. Also, with the market introduction of Serial ATA in 2003, the
> original ATA was retroactively renamed Parallel ATA (PATA).
>
>
> SCSI (Small Computer System Interface) is a set of standards for
> physically connecting and transferring data between computers and
> peripheral devices. The SCSI standards define commands, protocols, and
> electrical and optical interfaces. SCSI is most commonly used for hard
> disks and tape drives, but it can connect a wide range of other devices,
> including scanners and CD drives. The SCSI standard defines command sets
> for specific peripheral device types; the presence of "unknown" as one
> of these types means that in theory it can be used as an interface to
> almost any device, but the standard is highly pragmatic and addressed
> toward commercial requirements.
> --
> Regards Bill
>
Hi, Bill,
IDE was one of the early standards. It evolved way early in the
progress of computers:
1985: Control Data, Compaq Computer, and Western Digital collaborate to
develop the 40-pin IDE interface. IDE stands for Intelligent Drive
Electronics, more commonly known as Integrated Drive Electronics.
(http://pcworld.about.com/news/Sep132006id127105.htm)

This was the first attempt to standardize the interface between mass
storage and computer systems. Actually, though, a similar interface was
developed by several different companies around the 1978 timeframe. I
owned a Northstar single density hard-sectored 5.25" disk system for my
Altair 8080B that used a similar connector and controller around 1979.
I still have it by the way.

Basically the disks had little electronics on them. But they needed to
move the head to different tracks, keep track of the disk position,
write data to the disk, read data from the disk, change the data from a
serial stream to a parallel word, and pass that word back to the
computer. The IDE standard established the number of bits required to
perform these functions, a means to establish which disk to boot from
and a method to perform the dat transfer, along with all the stuff
needed to control disk speed, sector count, and buffer the data.

There was a half step between IDE and SCSI called ESDI. The design of
the original IDE had some size limitation that prevented disks from
growing to meet demands. I don't know too much about it any more, but I
did work on some systems that had it:

1985: Western Digital produces the first ESDI (Enhanced Small Device
Interface) controller board, which allows larger capacity and faster
hard drives to be used in PCs.
(http://pcworld.about.com/news/Sep132006id127105.htm)

SCSI was developed to address shortcomings in ESDI and add multiple
drive capability. I don't know for sure the drive count limitation on
SCSI, but I believe it was 7 or 15 originally, due to addressing bit
size.

1986: The official SCSI spec is released; Apple Computer's Mac Plus is
one of the first computers to use it.
(http://pcworld.about.com/news/Sep132006id127105.htm)

SCSI is a serial system, or at least it can be. It allows virtually
unlimited storage size, and has been implemented as a mother board in
several systems, where the drives plug directly into the frame. In
these cases the mother board also forms the means to permit hotplug, by
establishing the mechanical order of contact and the buffering of the
pins from spiking.

SCSI was originally deployed by apple as noted in the article, but also
in commercial applications. Sun Systems almost exclusively used SCSI
due to speed and capacity needed for their workstations. Also the SCSI
bus system was ideal for server systems where large quantities of data
had to be stored and quickly retrieved.

The standards for both are posted in the IEEE and ACM websites, along
with lots of good papers on the processes. Look between the years 1979
and 1985 if you are interested in the evolutionary history of the two
systems (and ESDI).

Regards,
Les H

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Old 02-02-2008, 07:24 PM
Les Mikesell
 
Default Difference between IDE and SCSI ??

Les wrote:



Can someone briefly explain to me the difference between an IDE (ATA)
and a SCSI device.



IDE was one of the early standards. It evolved way early in the
progress of computers:



SCSI was developed to address shortcomings in ESDI and add multiple
drive capability.


IDE drives tend to be cheaper and in a single user machine you might not
notice the difference. The big difference in practice is that IDE
controllers need more CPU intervention and there can only be one
outstanding command on a controller that can connect to two drives so
there is additional overhead waiting for availability. With scsi, the
same controller/cable can handle many drives and they can all be active
with the only contention being the total transfer throughput.


--
Les Mikesell
lesmikesell@gmail.com

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Old 02-02-2008, 08:12 PM
Ben Kamen
 
Default Difference between IDE and SCSI ??

Some BIG items are being left out of the SCSI discussion...

So allow me to add:

Unlike IDE, SCSI was more geared towards PERIPHERAL integration into computer
systems.


with IDE, you can (mostly) only hook up storage devices... but with SCSI,
you could hook up just about anything. Scanners, Network Interfaces, Drives,
Tape backups, the list goes on and on becauce SCSI that's what SCSI was designed
for.


Now, I don't know if I would say IDE was around that much longer than SCSI as
a defined standard. But, the SASI interfaces and other MF style drives had some
sort of similar setup where the drive was dumb and needed some sort of controller.

I still have the SCSI -> MFM controllers for my Atari's back in the mid-80's
(which when they were cheap for Atari in the mid-80's, that leads me to believe
SCSI was around a bit longer than IDE as a "standard").

In fact, on my Atari, over 1 SCSI bus, I had hard drives, tape drives and
Syquest Removable storage as well as CD-ROM's and a scanner. All on 1 system!


Original SCSI was limited to 8 devices (3 bit addressing with 1 being taken up
by the "host adapter) leaving 7 more for devices (or other hosts! do that with IDE!)


SCSI Wide used 4 bit addressing (16 devices) and a 16bit data bus effectivly
doubling the data tranfer rate.

In the beginning, SCSI was always faster than IDE because the intelligence of
the drives (remember, IDE tends to be dumb as it's controlled by the host), that
lent the drives to be more expensive. So think "server" and thus smarter, more
expensive also demanded "faster".


Eventually IDE caught up because the demand required it and the scale of
production brought the price of the mechs down (which is why they're so cheap
these days even though as an interface SCSI is better - but the point is moot

for the typical home/biz user).

Now, I've had machines with multiple SCSI host adaptors (they aren't
"controllers" because the peripherals control themselves. The computer is more

a peer in this relationship) where I've had 6 or 7 devices hooked to a single
SCSI Fast/Wide bus.

Good stuff SCSI was. Highly underused but never overrated.

-Ben


--
Ben Kamen - O.D.T., S.P.
================================================== ====================
Email: bkamen AT benjammin DOT net Web: http://www.benjammin.net
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Old 02-02-2008, 08:13 PM
"Mikkel L. Ellertson"
 
Default Difference between IDE and SCSI ??

Les wrote:

Hi, Bill,
IDE was one of the early standards. It evolved way early in the
progress of computers:
1985: Control Data, Compaq Computer, and Western Digital collaborate to
develop the 40-pin IDE interface. IDE stands for Intelligent Drive
Electronics, more commonly known as Integrated Drive Electronics.
(http://pcworld.about.com/news/Sep132006id127105.htm)

This was the first attempt to standardize the interface between mass
storage and computer systems. Actually, though, a similar interface was
developed by several different companies around the 1978 timeframe. I
owned a Northstar single density hard-sectored 5.25" disk system for my
Altair 8080B that used a similar connector and controller around 1979.
I still have it by the way.


Basically the disks had little electronics on them. But they needed to
move the head to different tracks, keep track of the disk position,
write data to the disk, read data from the disk, change the data from a
serial stream to a parallel word, and pass that word back to the
computer. The IDE standard established the number of bits required to
perform these functions, a means to establish which disk to boot from
and a method to perform the dat transfer, along with all the stuff
needed to control disk speed, sector count, and buffer the data.

There was a half step between IDE and SCSI called ESDI. The design of
the original IDE had some size limitation that prevented disks from
growing to meet demands. I don't know too much about it any more, but I
did work on some systems that had it:

1985: Western Digital produces the first ESDI (Enhanced Small Device
Interface) controller board, which allows larger capacity and faster
hard drives to be used in PCs.
(http://pcworld.about.com/news/Sep132006id127105.htm)

SCSI was developed to address shortcomings in ESDI and add multiple
drive capability. I don't know for sure the drive count limitation on
SCSI, but I believe it was 7 or 15 originally, due to addressing bit
size.


1986: The official SCSI spec is released; Apple Computer's Mac Plus is
one of the first computers to use it.
(http://pcworld.about.com/news/Sep132006id127105.htm)

SCSI is a serial system, or at least it can be. It allows virtually
unlimited storage size, and has been implemented as a mother board in
several systems, where the drives plug directly into the frame. In
these cases the mother board also forms the means to permit hotplug, by
establishing the mechanical order of contact and the buffering of the
pins from spiking.

SCSI was originally deployed by apple as noted in the article, but also
in commercial applications. Sun Systems almost exclusively used SCSI
due to speed and capacity needed for their workstations. Also the SCSI
bus system was ideal for server systems where large quantities of data
had to be stored and quickly retrieved.


The standards for both are posted in the IEEE and ACM websites, along
with lots of good papers on the processes. Look between the years 1979
and 1985 if you are interested in the evolutionary history of the two
systems (and ESDI).

Regards,
Les H

Are you sure about your time line? I can remember using SCSI drives
while PC's were still using MFM and RLL drives, long before IDE
drives showed up. I could have sworn that SCSI drives pre-dated the
IBM PC.


Mikkel
--

Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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Old 02-02-2008, 08:36 PM
Aaron Konstam
 
Default Difference between IDE and SCSI ??

On Sat, 2008-02-02 at 15:13 -0600, Mikkel L. Ellertson wrote:
> Les wrote:
> > Hi, Bill,
> > IDE was one of the early standards. It evolved way early in the
> > progress of computers:
> > 1985: Control Data, Compaq Computer, and Western Digital collaborate to
> > develop the 40-pin IDE interface. IDE stands for Intelligent Drive
> > Electronics, more commonly known as Integrated Drive Electronics.
> > (http://pcworld.about.com/news/Sep132006id127105.htm)
> >
> > This was the first attempt to standardize the interface between mass
> > storage and computer systems. Actually, though, a similar interface was
> > developed by several different companies around the 1978 timeframe. I
> > owned a Northstar single density hard-sectored 5.25" disk system for my
> > Altair 8080B that used a similar connector and controller around 1979.
> > I still have it by the way.
> >
> > Basically the disks had little electronics on them. But they needed to
> > move the head to different tracks, keep track of the disk position,
> > write data to the disk, read data from the disk, change the data from a
> > serial stream to a parallel word, and pass that word back to the
> > computer. The IDE standard established the number of bits required to
> > perform these functions, a means to establish which disk to boot from
> > and a method to perform the dat transfer, along with all the stuff
> > needed to control disk speed, sector count, and buffer the data.
> >
> > There was a half step between IDE and SCSI called ESDI. The design of
> > the original IDE had some size limitation that prevented disks from
> > growing to meet demands. I don't know too much about it any more, but I
> > did work on some systems that had it:
> >
> > 1985: Western Digital produces the first ESDI (Enhanced Small Device
> > Interface) controller board, which allows larger capacity and faster
> > hard drives to be used in PCs.
> > (http://pcworld.about.com/news/Sep132006id127105.htm)
> >
> > SCSI was developed to address shortcomings in ESDI and add multiple
> > drive capability. I don't know for sure the drive count limitation on
> > SCSI, but I believe it was 7 or 15 originally, due to addressing bit
> > size.
> >
> > 1986: The official SCSI spec is released; Apple Computer's Mac Plus is
> > one of the first computers to use it.
> > (http://pcworld.about.com/news/Sep132006id127105.htm)
> >
> > SCSI is a serial system, or at least it can be. It allows virtually
> > unlimited storage size, and has been implemented as a mother board in
> > several systems, where the drives plug directly into the frame. In
> > these cases the mother board also forms the means to permit hotplug, by
> > establishing the mechanical order of contact and the buffering of the
> > pins from spiking.
> >
> > SCSI was originally deployed by apple as noted in the article, but also
> > in commercial applications. Sun Systems almost exclusively used SCSI
> > due to speed and capacity needed for their workstations. Also the SCSI
> > bus system was ideal for server systems where large quantities of data
> > had to be stored and quickly retrieved.
> >
> > The standards for both are posted in the IEEE and ACM websites, along
> > with lots of good papers on the processes. Look between the years 1979
> > and 1985 if you are interested in the evolutionary history of the two
> > systems (and ESDI).
> >
> > Regards,
> > Les H
> >
> Are you sure about your time line? I can remember using SCSI drives
> while PC's were still using MFM and RLL drives, long before IDE
> drives showed up. I could have sworn that SCSI drives pre-dated the
> IBM PC.
>
> Mikkel
The iBM PC waas released in 1982 with dissk pased PC's shortly after
using IDE interface. SCSI was considerably later.



--
================================================== =====================
I can resist anything but temptation.
================================================== =====================
Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam@sbcglobal.net

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Old 02-02-2008, 09:17 PM
Les Mikesell
 
Default Difference between IDE and SCSI ??

Ben Kamen wrote:

In the beginning, SCSI was always faster than IDE because the
intelligence of the drives (remember, IDE tends to be dumb as it's
controlled by the host), that lent the drives to be more expensive. So
think "server" and thus smarter, more expensive also demanded "faster".


Scsi needs less intervention by the main CPU but that doesn't
necessarily translate to 'faster'. The overall time is going to be
limited by the seek and transfer rate of the drive itself, which is
often identical between IDE and Scsi models. The tradeoff in cost of
putting intelligence on peripheral devices and the value of those extra
main CPU cycles (often spent waiting idly in is single-user computer
anyway) has bounced back and forth over the years. In a file server
with lots of drives, scsi is usually a big win compared to typical ide
controllers because it lets all the disks seek independently at the same
time. However even that isn't quite so simple, since specialized
controllers like the 3ware raid cards can do the same with ide drives
and also offload the work from the main CPU.


--
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lesmikesell@gmail.com

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Old 02-02-2008, 09:22 PM
William Case
 
Default Difference between IDE and SCSI ??

Thanks Les;

On Sat, 2008-02-02 at 11:57 -0800, Les wrote:
> On Sat, 2008-02-02 at 13:39 -0500, William Case wrote:
> > Hi;
> >
> > Can someone briefly explain to me the difference between an IDE (ATA)
> > and a SCSI device. After having done due diligence with google searches
> > etc., I am still in a quandary. Nothing I read seems to be consistent.
> > Every time I think I have it figured out, I read a reference that calls
> > for or lists IDE devices that I think should be a SCSI reference and
> > vice versa. Even going to the various standards sites doesn't clarify
> > it for me. In fact it makes it more confusing.

I have used the pcguide and the pcworld site. Along with Wikipedia, I
always go there first. The summary of those sites seems to be the
following:

IDE ==> SCSI ==> (P)ATA. That is simple and fairly easy to follow. The
advancements from one to the next at first seem obvious. So let me put
the question in another way.

I have two Maxtor 40 Gb drives and AMD 64 X2 CPU on an ASUS M2NPV-VM
motherboard. I am using F8 as my operating system.

How come? :
My Hardware browser, under 'IDE Controllers' lists, nVidia Corporation
MCP51 IDE; while /sys/bus/scsi/devices/ lists my two drives as SCSI
devices. If I look in /dev/disk/by-id they are listed as
"ata-Maxtor-5T040 ..." and "ata-Maxtor-6E040...".

I also have seen them or similar drives referred to as any of IDE,
(P)ATA or SCSI. I have also seen the terms used apparently
interchangeably over the last 2 or 3 years. I would have to go search
to quote exactly where, but I do remember the use of these terms.

I am not confusing them with SATA drives which are something else again.
If they are all one and the same, I will henceforth just mentally
substitute the word PATA for any of the other two designations. But I
have a sneaking suspicion they are not exactly the same and should not
be used interchangeably on a modern system as they appear they sometimes
are.

My original question was not to have someone else do my investigation
for me, but to either give me reassurance that all three, IDE, PATA and
SCSI are exactly the same thing and can be used interchangeably on a
current system, or to point out where I have missed the difference and
when I should use one term over the other.


--
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Old 02-02-2008, 10:23 PM
Ben Kamen
 
Default Difference between IDE and SCSI ??

Les Mikesell wrote:

Ben Kamen wrote:

In the beginning, SCSI was always faster than IDE because the
intelligence of the drives (remember, IDE tends to be dumb as it's
controlled by the host), that lent the drives to be more expensive. So
think "server" and thus smarter, more expensive also demanded "faster".


Scsi needs less intervention by the main CPU but that doesn't
necessarily translate to 'faster'. The overall time is going to be
limited by the seek and transfer rate of the drive itself, which is
often identical between IDE and Scsi models. The tradeoff in cost of
putting intelligence on peripheral devices and the value of those extra
main CPU cycles (often spent waiting idly in is single-user computer
anyway) has bounced back and forth over the years. In a file server
with lots of drives, scsi is usually a big win compared to typical ide
controllers because it lets all the disks seek independently at the same
time. However even that isn't quite so simple, since specialized
controllers like the 3ware raid cards can do the same with ide drives
and also offload the work from the main CPU.


True true... the drive is ultimately a bottleneck... I should have mentioned.

but let's talk 20 years ago. I realize a lot of the technology has caught up
to today. A lot of the performance arguments these days are kinda moot.

Heck, I have 3 125GB IDE drives mounted onto my RS/6000's SCSI bus with SCSI-IDE
adapters as it was cheaper to get the adapters with drives than just large SCSI
drives. Funky.


-Ben

--
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================================================== ====================
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Old 02-03-2008, 01:12 AM
Les
 
Default Difference between IDE and SCSI ??

On Sat, 2008-02-02 at 15:13 -0600, Mikkel L. Ellertson wrote:
> Les wrote:
> > Hi, Bill,
> > IDE was one of the early standards. It evolved way early in the
> > progress of computers:
> > 1985: Control Data, Compaq Computer, and Western Digital collaborate to
> > develop the 40-pin IDE interface. IDE stands for Intelligent Drive
> > Electronics, more commonly known as Integrated Drive Electronics.
> > (http://pcworld.about.com/news/Sep132006id127105.htm)
> >
> > This was the first attempt to standardize the interface between mass
> > storage and computer systems. Actually, though, a similar interface was
> > developed by several different companies around the 1978 timeframe. I
> > owned a Northstar single density hard-sectored 5.25" disk system for my
> > Altair 8080B that used a similar connector and controller around 1979.
> > I still have it by the way.
> >
> > Basically the disks had little electronics on them. But they needed to
> > move the head to different tracks, keep track of the disk position,
> > write data to the disk, read data from the disk, change the data from a
> > serial stream to a parallel word, and pass that word back to the
> > computer. The IDE standard established the number of bits required to
> > perform these functions, a means to establish which disk to boot from
> > and a method to perform the dat transfer, along with all the stuff
> > needed to control disk speed, sector count, and buffer the data.
> >
> > There was a half step between IDE and SCSI called ESDI. The design of
> > the original IDE had some size limitation that prevented disks from
> > growing to meet demands. I don't know too much about it any more, but I
> > did work on some systems that had it:
> >
> > 1985: Western Digital produces the first ESDI (Enhanced Small Device
> > Interface) controller board, which allows larger capacity and faster
> > hard drives to be used in PCs.
> > (http://pcworld.about.com/news/Sep132006id127105.htm)
> >
> > SCSI was developed to address shortcomings in ESDI and add multiple
> > drive capability. I don't know for sure the drive count limitation on
> > SCSI, but I believe it was 7 or 15 originally, due to addressing bit
> > size.
> >
> > 1986: The official SCSI spec is released; Apple Computer's Mac Plus is
> > one of the first computers to use it.
> > (http://pcworld.about.com/news/Sep132006id127105.htm)
> >
> > SCSI is a serial system, or at least it can be. It allows virtually
> > unlimited storage size, and has been implemented as a mother board in
> > several systems, where the drives plug directly into the frame. In
> > these cases the mother board also forms the means to permit hotplug, by
> > establishing the mechanical order of contact and the buffering of the
> > pins from spiking.
> >
> > SCSI was originally deployed by apple as noted in the article, but also
> > in commercial applications. Sun Systems almost exclusively used SCSI
> > due to speed and capacity needed for their workstations. Also the SCSI
> > bus system was ideal for server systems where large quantities of data
> > had to be stored and quickly retrieved.
> >
> > The standards for both are posted in the IEEE and ACM websites, along
> > with lots of good papers on the processes. Look between the years 1979
> > and 1985 if you are interested in the evolutionary history of the two
> > systems (and ESDI).
> >
> > Regards,
> > Les H
> >
> Are you sure about your time line? I can remember using SCSI drives
> while PC's were still using MFM and RLL drives, long before IDE
> drives showed up. I could have sworn that SCSI drives pre-dated the
> IBM PC.
>
> Mikkel
> --
All these standards evolved almost simultaneously, but the patents and
use by the public was what is documented by PC World Magazine. I had
subscribed to Byte (when it was folded and stapled with no
advertisements), and Dr Dobbs Journal when it was still labeled Dr.
Dobbs Journal of Computer Calisthenics and Orthodontia, and watched the
evolution of many things, including C, PASCAL, ADA and other languages.
But the time line I used was from PC World. That is why I noted the
URL. Check it out.

Regards,
Les H

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