Rounding Out Your IDE Cables

BrookHarty sent us a story that proves that sometimes it's the little things that are clever. Are you as annoyed as I am that those pesky IDE cables are big flat things that are hard to move around? Well, here's a HOWTO that explains, well, how to round them out! It won't solve global warming or change the world. But dang it, that's cool.

Comments

IDE not ATA66

[don_carnage]

From everything I've read, it's a pretty easy and painless operation with IDE cables, but don't touch those ATA66 cables unless you have a lot of money to spare.

The trick is to use your fingers (if you can) instead of a knife to avoid severing a cable.

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Re:It's a square wave - not a sine wave.

[willy_me]

Since wavelength at 66MHz is about 4.5 meters, I don't think transmission line effects are all that important on short 1 foot cable (yes I realize SCSI needs terminators but that is slightly different).

Just in case you didn't know, a 66MHz square wave is made up of several (ok, really unlimited) different sine waves. You need to look at the rising and falling times of the signal if you want to calculate the RF produced.

Also, look at an FM transmitter. One inch of wire is enough to transmit a signal!!! Even AM doesn't require that big an antenna while it operates at a blazing 1MHz. The 66MHz signal will most definitely be producing a ton of RF.

The ground lines are nothing more than shielding in this case.

Are you serious? You really think putting a wire next to another wire will provide shielding? No, sorry bud, that's just not how it works. Shielding can be provided by completely surrounding the transmission line with a ground wire - like with your TV cable or RCA wires. An extra wire does nothing to stop RF.

So why do people put ground wires by transmission wires? It's actually not usually like that. The two wires aren't positive + ground, they're a differential pair, like your ethernet cable. The idea being that one wire is more positive then the other. So then when a pile of RF comes along and jolts the voltage up in those lines by 20%, the data isn't lost because the relative voltage of the two lines isn't effected. The second line protects against data corruption, not RF production.

This reminds me of a cool lab I did back when I was in school. Our class wired several RS232-RS422 converters to connect to the serial ports of different PCs. We then connected them all to a single differential pair (ie, two wires). After writing some software we had our entire lab networked via the serial port! Ok, it sounds lame but was great fun to implement.

Willy

FireWire speeds / FireWire advantages

[Tumbleweed]

IEEE1394a (current standard) tops out at 400Mbps (megaBITS). The upcoming IEEE1394b standard spans 800-3200Mbps.

SCSI drives are currently made with interfaces for 160MBps (megaBYTES), and the newest standard - don't know if it's finalized yet - is 320MBps.

Obviously, hard drives cannot transfer at anywhere NEAR those rates, BUT, there's still a reason for them: multiple drives! With the advent of RAID (ATA RAID controllers built-in to motherboards are all the rage now), then these speeds become much more justifiable.

The problem with FireWire hard drives is, as far as I know, there aren't any that have NATIVE FireWire interfaces on them - they're still ATA native devices with FireWire converters built-on to them (usually made by TI). From what I've read online, the current crop of TI chips aren't too efficient, but the next generation (due now or soon) are much better. Nevertheless, I'd feel better about harddrives (I prefer IBM these days) with native FireWire interfaces. Let's hope IEEE1394b gets here right quick.

The advantages of FireWire are numerous:

• You don't need a computer (you can connect, for example, a fireware hard drive directly to your firewire video camera or digital still camera, or whatever - no computer in between needed)
• hot-plug capability built right in without any extra work necessary
• you can chain I think up to 63 devices to it - that blows away scsi, ata, and I think serial-ata
• cable lengths _much_ better than SCSI or ATA
• say goodbye to ribbon cables

That's all I can think of right now - I'm sure there are more.

The Dumbshit way of doing things...

[human bean]

The reason that ribbon cables are flat is to preserve the phase relationships of multiple signals in a cable while at the same time reducing in-cable interference to a reasonable level. As speeds for data transfer become higher and higher, this becomes more and more important. Fortunately, most data transfers are now intelligent enough that error correction takes care of most of the glitches that used to stop systems in their tracks.

Rounding cables like this is a time-wasting method of destroying all that paid-for engineering. Try one of these instead:

1. Look in the Newark (or similar) catalog and buy one, for pity sake.

2. Take the long section (what you are most concerned with), carefully fold it up lengthwise, and slide it into a length of half-inch split loom tube (any good parts store for about fifteen cents).

Either of these will get you where you wanted to be, which was moving that cable out of the way. Also note that IDE and especially ATA cables must be cut to a certain length to avoid possible SWR problems. You might also look up the proper folding and routing of ribbon cables, which seems to be a lost art among PC manufacturers these days.

What if you're too lazy?

[Anonymous Coward]

Here's place that sells them pre-rounded. You can get rounded cables for ATA33, ATA66/100, floppy, and SCSI 50-pin.

Cable Impedance

[uksv29]

At 66MHz IDE cables are going to look like a transmission line and I assume that is why there are so many earth connections in parallel with the signal wires. If you separate them then you could end up with a mismatch, more RF interference and possibly data corruption.

If you are going to try it out then backup your data first and make sure that you have a spare cable in case you break something