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Troll · Jul 11, 2001, 06:13 AM

I recently bought an AB Soft mini USB hub for my iMac. My Que! USB CD writer can only burn via the hub at double speed (2x) whereas it can burn at 4x plugged directly into the iMac.

AB Soft says that this is a limitation of ALL USB hubs. 2x is the speed limit for ANY USB hub. Is this true?

They didn't mention this limitation on the box, so if it's not true, I will send it back and look for a faster version.

milhaus · Jul 11, 2001, 06:44 AM

I've burnt from a Lacie USB Burner at 4x through an Asante Hub, though it is a little less reliable (sometimes when burning VCDs I had to step down.)

Han's Hands on Leia · Jul 12, 2001, 01:27 AM

Is your hub "powered"?

Cipher13 · Jul 12, 2001, 02:37 AM

A hub splits the bandwidth of one USB channel.

You get a dedicated 11.5Mb/s from the computers USB port.

From a hub you have to divide that by the amount of devices plugged into it.
If a device is on the hub but not using it, only very little bandwidth will be taken, and some devices, such as printers, don't use heaps anyway.

If you only have the burner in the hub you MAY get a 4X burn. But that defies the entire purpose of the hub.

Troll · Jul 12, 2001, 06:10 AM

The Hub has a switch for powered or unpowered. It's currently in the NOT powered position. Would it make a difference to the bandwidth by plugging the hub in? Doubt it! I can't burn faster than 2x with just my iSub and the burner (neither of which need power from the hub) plugged into the hub. So it sounds like the iSub is sucking bandwidth?!

Maybe an option is to power the hub, plug my keyboard and the iSub into it(I assume the keyboard uses very little bandwidth) and free the other USB plug on the iMac for the burner?

Troll

Cipher13 · Jul 12, 2001, 06:28 AM

Originally posted by Troll:
<STRONG>The Hub has a switch for powered or unpowered. It's currently in the NOT powered position. Would it make a difference to the bandwidth by plugging the hub in? Doubt it! I can't burn faster than 2x with just my iSub and the burner (neither of which need power from the hub) plugged into the hub. So it sounds like the iSub is sucking bandwidth?!

Maybe an option is to power the hub, plug my keyboard and the iSub into it(I assume the keyboard uses very little bandwidth) and free the other USB plug on the iMac for the burner?

Troll</STRONG>

Nope, don't do that.

The keyboard MUST be plugged into the computer - so must the hub.
Yeah, the iSub will suck bandwidth - as will ANY device. Minute amounts, but still... I mean the iSub, when active, may pull a fair bit. I don't know.

Could you list all your USB peripherals here, and also, when you say there is an option to power the hub - that means you have a power adapter for it, right?

If the burner isn't bus powered, chances are powering the hub won't make enough difference to worry about - but you never know.

Troll · Jul 12, 2001, 07:32 AM

Could you list all your USB peripherals here

USB 1 has Apple iMac Keyboard (Blueberry not Pro). Keyboard has mouse plugged into it.
USB 2 has AB Soft USB Hub plugged into it with 4 ports. iSub and Que! Drive USB CD Writer are permanently plugged in to the hub. Every now and then, I plug in an Epson 714c printer and a MOTU 2 port midi hub. Have only ever tried the burner with the iSub plugged in, never with any of the others on.

when you say there is an option to power the hub - that means you have a power adapter for it, right?

Correct but since the iSub and the Burner are powered, I've never even taken the power adapter out of the box. Will try it and see if it makes a difference.

The keyboard MUST be plugged into the computer

I thought the problem with not plugging the keyboard into the computer was insufficient power to the keyboard via the hub. Will the hub not give enough or is there a more serious risk?

GetSome681 · Jul 12, 2001, 08:38 AM

The Keyboard doesn't HAVE to be plugged directly into the computer. It seems mine isn't, and it works just fine!

Troll · Jul 12, 2001, 04:54 PM

Notice how every USB peripheral manufacturer tells you that their peripheral HAS to be plugged into the computer?

Here are the results of my experiments:

1) USB 1 - keyboard; USB2 - adapter-powered hub; HUB - burner and iSub.
RESULT: Buffer underrun at 4x on the burner.

2) USB1- adapter-powered hub; USB2 - burner; HUB - keyboard and iSub. (Despite fears that my iMac would go up in flames like a Powerbook adapter (fears generated by Cipher13's post))
RESULT: Keyboard works fine and no underruns burning at 4x with iTunes exercising the iSub. My solution!

3) USB1 - keyboard; USB2 - hub; HUB - burner, NO iSUB
RESULT: No buffer underrun at 4x.

Seems that the iSub saps sufficient bandwidth to disturb the burner if they're both on the hub which seems strange, but there you have it.

MORAL OF THE STORY:
AB Soft were wrong. Cipher13 and Milhaus were right. I got their own Hub to burn at 4x. Thanks for the help Milhaus, Hands on Lea, Cipher 13 and GetSome681

Kryton · Jul 14, 2001, 05:24 PM

I too had nightmares with USB products (running through the hub on my monitor in my case).

Yes, all manufacturers say their hubs comply with the latest standards but the reality is that there is a huge difference between the capability of most hubs.

When I investigated I found that only the Macalley hub (the seven port hub, I think) permitted booting via the keyboard which confirms that it's not absolutely required to have the keyboard plugged into the computer. Xircom took too long to answer my enquiries and then sent me the wrong compatibilty listing. Yes they have compatibility listings and we're talking about a standard here (well done Intel). So much for USB being 'universal'.

Most higher bandwidth product manufacturers tell you to plug their products directly into the computer (so much for 127 pieces of hardware getting along just fine).

I finally opted for a Belkin four port hub that eliminated ALL my previous problems but gave me one new one (it won't allow sleep mode to work) that I can live with.

I have it set to external power and all four ports are occupied by the following:

Umax scanner
Epson 900 printer
LaCie Floppy drive
ZIP 100

Now the reason of this post. It might be worthwhile swapping the cables into the different ports on the hub because I'm told that not all ports on hubs get treated the same. The general saying is that higher bandwidth products should go into ports one or two on the hub.

I haven't got a USB burner so can't offer any results with one on a Belkin hub.

Hope this helps.

[ 07-14-2001: Message edited by: Kryton ]

Cipher13 · Jul 19, 2001, 08:52 AM

GetSome - YES, the keyboard HAS TO BE plugged into the computer.

If you wanna run it off a hub, fine, but you will be sorry.

Troll - glad to help

milhaus · Jul 20, 2001, 12:48 PM

You've just detailed some of the major problems with USB audio - because its a consistent draw on the system. I've had problems trying to print in with Toast in the background, with a USB printer plugged into the hub. Best go firewire.