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Old 10-01-2009, 01:56 AM   #1 (permalink)
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Unhappy Can someone PLEASE explain SCSI, IDE & bus?

Im taking classes to get my certs. first is A+ and Im half way through essentials & its brought up here and there. I would just like a straight forward, understandable ( im not a computer geek.... yet ) answer. and also what is the diff between SCSI & IDE? Is it refering to the cable/ribbon that connects the device to the mobo or is it the device itself? sorry if this is a dumb question I just want to be able to COMPLETELY understand everything you know
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Old 10-01-2009, 02:16 AM   #2 (permalink)
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Default Re: Can someone PLEASE explain SCSI, IDE & bus?

They are both ways to connect hard drives, cd drives etc. to your computer to move data. They are both older formats. SCSI will be seen more on servers and IDE was more prevalent. In most home computers if you wanted to run SCSI you need to buy a add in card.

both have essentially been replaced with SATA and SAS.

SCSI - Wikipedia, the free encyclopedia
Parallel ATA - Wikipedia, the free encyclopedia
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Old 10-01-2009, 04:58 AM   #3 (permalink)
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Default Re: Can someone PLEASE explain SCSI, IDE & bus?

Quote:
Originally Posted by Hefemeister View Post
They are both ways to connect hard drives, cd drives etc. to your computer to move data. They are both older formats. SCSI will be seen more on servers and IDE was more prevalent. In most home computers if you wanted to run SCSI you need to buy a add in card.

both have essentially been replaced with SATA and SAS.

SCSI - Wikipedia, the free encyclopedia
Parallel ATA - Wikipedia, the free encyclopedia

SCSI also had/has a faster bus speed (transportation speed) and SCSI hard drives spin faster...
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Old 10-01-2009, 05:00 AM   #4 (permalink)
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Default Re: Can someone PLEASE explain SCSI, IDE & bus?

correct. That is why you primarily saw then in Servers. The Cheetahs ran 15K rpm if memory serves me correctly.
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Old 10-01-2009, 05:25 AM   #5 (permalink)
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Default Re: Can someone PLEASE explain SCSI, IDE & bus?

Not just cheetahs, there are of drives that spin at 15000rpm and 10000rpm but really the main reason for using SCSI in servers is that you can have up to 16 devices on each channel (one is taken up by the controller though) as opposed to 2 on IDE.
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Old 10-01-2009, 03:21 PM   #6 (permalink)
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Default Re: Can someone PLEASE explain SCSI, IDE & bus?

Ok so let me verify, IDE & SCSI are just the cable that connects certain devices (HD, FDD, CDROM) to the mobo. k so what about bus? what is it? is it a physical component or is it something like how horsepower is related to a car? sorry for these questions that seem second nature to you guys
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Old 10-01-2009, 04:31 PM   #7 (permalink)
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Default Re: Can someone PLEASE explain SCSI, IDE & bus?

A bus is a group of tiny electrical paths on a motherboard. There are different types of busses; an address bus, which the CPU uses for sending physical address messages to allocate memory. An external data bus is used for transmitting data over.

SCSI is a type of technology that allows the SCSI devices to be "chained" together. One implementation of SCSI can link up to 16 drives together. It has a relatively fast transfer rate, although todays newer drives (SATA) are doing what SCSI was doing before it, and is growing more in popularity every day.

IDE is the older yet still highly supported technology for connecting hard drives, cd roms, etc. So its not just a cable; IDE stands for "Integrated Drive Electronics". SATA is becoming more common but IDE is still common on all ATX motherboards, although their are predications that SATA will ultimately replace IDE altogether.
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Old 10-01-2009, 07:19 PM   #8 (permalink)
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Default Re: Can someone PLEASE explain SCSI, IDE & bus?

so could someone explain a front side bus? would it be safe to say that SCSI, IDE, SATA & the likes are like the idea or technology as you said you simply have to choose the right cable to achieve your desired outcome. if you just need a simple set up for home or small office you would want to use an IDE interface but if you wanted a faster more diverse setup like in a larger business you would utilize SCSI?
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Old 10-01-2009, 07:44 PM   #9 (permalink)
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Default Re: Can someone PLEASE explain SCSI, IDE & bus?

(from Wikipedia)

The frontside bus is the data path between the CPU and Northbridge. The Northbridge is the part of the chipset that handles data between the CPU, and RAM, among other things.

These days, the Southbridge is taking on more of the role that used to be more exclusive to the Northbridge. So much so that now you can find fans on the North and Southbridge chips, because they got hot like their partner, the CPU. (*"chipset" refers to the combination of the North and South bridge chips).

Some businesses integrate IDE drives alongside SCSI drives; I had a college professor who does networking for a hospital by day, and he said they use both types of drives. The reason is more than needs to be stated here and would be off-point some anyway.

IDE was before PATA and SATA. PATA used parallel data bit travel between the drive, drive controller and data bus. It seemed like the way to go when it first came out, but because some bits would arrive at their destination ever-so-slightly at different "times", the error correction that was needed to put the bits together to make a cohesive chunk of data was slower than it needed to be, so SATA came along (which is serial) and even though data travels in serial form, it actually is quicker than PATA because there is no error correction needed spread out over different bus signals as PATA was.

SCSI was the reigning champ at one time, and is still used a fair amount still. Like SCSI, SATA drives are hotswapable. IDE is not hotswapable, and I believe PATA is not either.

Businesses could (and do) use these different technologies, but usually if you see SCSI in businesses it is in a RAID array.
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Old 10-02-2009, 09:20 AM   #10 (permalink)
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Default Re: Can someone PLEASE explain SCSI, IDE & bus?

Below is what I think research is something I don't do until I really really need to so all of this is the conclusions I have come to from my experience alone.

The problem is that I think some of these things are physical and others are technically specifications or protocols but because the physical objects that implement these specifications/protocols are so often referred to by the name of the spec they become interchangable. For example I believe SCSI is more like a specifcation for moving data than a spec for drives and cables themselves.
So there is a "theory world" and a "real world" in theory world I think IDE and SCSI are data moving/drive addressing specifications whereas ATA (later also called PATA), SATA, SAS, and about a dozen different SCSI terms describe physical things (cables, connectors etc).
In the real world though IDE=ATA and a SCSI drive is a drive with either a 68 (non-hotswappable) or 80 pin (hot swappable) parallel SCSI connector (50 pin is sometimes used for external drives like eSATA is used today).

IDE, ATA, PATA ~ 34 pin floppy connector, 40 pin ATA66 and ATA100 connectors, 80 pin ATA 133 connectors ~ (non hotswappable, 2 devices per channel)
SATA ~ 7 pin connectors ~ (hotswappable, 1 device per channel)
SCSI ~ 50 pin external connectors (self-terminated), 68 pin internal connectors, 80 pin hotswap connectors ~ (require termination, 16 devices per channel)
SAS ~ 7 pin connector, mini-SAS connector (4 channels on one cable) ~ (32 devices per channel, hot swappable)
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