Will this layout with a remote USB hub work?

**NoPistonPC** · 05-20-2004, 03:26 AM

My car is tiny (RX-7 FD) and I live in a not-so-friendly neighborhood. So two things I have to keep in mind when designing my CarPC are: compactness and security.

Therefore, I can't have anything visibly out in the open. Also, in terms of storage, I have a locked glove compartment which can just barely fit an EPIA mini-ITX board, and a locked storage bin (behind the passenger seat) that is about the size of a shoebox. Also, I have some space behind the touchscreen (installed in a double-din slot where my headunit used to be) to put the PSU and a fan.

The best way I could think of to fit everything was to use only USB devices for everything (including HDD storage) and run a single USB cable to the storage bin where I would put a 6-port hub and all my devices. So it would look like this:

(NOTE: I know there are a LOT of components missing from this diagram, like fuses, SDC, audio components, touchscreen, etc. I just wanted to focus on the USB hub related issues)

I know there will be a lot of current draw on the 5V rail due to all these USB devices and the USB hub. However, I will be using an Arise MPD-810H which provides up to 14A on the +5V rail. I think that should be plenty of juice, but please correct me if I'm wrong.

So, my biggest concerns are the following:

1) Is the 15' USB cable going to be too long?
2) My EPIA P4-ITX has a bios setting for booting off a USB-HDD, but can anyone confirm that this actually works? I will not have any IDE drives installed.
3) Will the 14A +5V rail provide enough power to drive everything in the rear storage bin (6-port USB Hub, plus 3.5" USB HDD, plus 4 USB devices)?
4) Will all of these devices sharing the same USB port hurt performance in any way?
5) Will need to use some sort of relay switch to completely cut power to the USB port when the computer is turned off? I heard that most new motherboards don't cut power to the +5VSB rail after power down. This would kill my battery.

Thanks for any advice.

**Mr Castulucci** · 05-20-2004, 03:50 AM

Well, I can tell you that 15' is OK for a USB cable. The maximum length is actually 5 meters, which is a few inches longer than 15'.

Not sure about the rest of your questions

**jusatry** · 05-20-2004, 04:23 AM

you may want to run an extension from the 5V rail of the PSU to the shoebox - im pretty sure the audigy is gonna need external power, along with the HDD (may be 12V, so maybe need to run a full molex). Also - you may want to get a USB "repeater", which strengthens the USB signal. Also, a simple SDC (mpegbox.com) may solve your problems with cutting power to the USB. Just use it as a relay.

Good luck!

**NoPistonPC** · 05-20-2004, 05:51 AM

Mr. C and jusatry, thanks for the replies.

I was already planning on powering the USB devices that required external power off an another extended 5V rail, but I didn't want to clutter the diagram. But thanks for pointing out that I'd also need a 12V line for the HDD...I completely forgot about that one. Damn...maybe I should just go with a laptop drive instead ($$$

).

Regarding the SDC, I already have an ITPS (with regulator bypassed) that I plan to use. I believe it will work the same way as Mucha's SDC. I had always assumed that these SDCs would completely cut power to the motherboard, but when I saw this thread, I became a little worried. Is this only a problem with OPUS power supplies (since they have a built-in SDC)?

Also, does anyone have experience with booting off a USB-HDD?

**Confused** · 05-20-2004, 06:27 AM

Run a full 4 wires (+12v, 0, 0, +5v) to the storage bin, which is cut off with the power supply, and you'll be fine

I would make sure that you've got a powered USB2 hub, as unpowered will not provide enough power for everything that you need to use.

Garry

**NoPistonPC** · 05-20-2004, 07:29 AM

Confused, I believe the problem is that even with the USB hub's 5v supply cutoff, it will still draw power from the USB cable plugged into the USB port on the motherboard. That's why in the thread I mentioned above, Ricky and gospeedracer were describing a setup where a relay driven by +5V from a PSU molex would be used to switch the +5V power line going into the USB port. So, I guess my question is: will I have this problem if I use an ITPS as my SDC? That is, does the ITPS completely shut off power to the PSU, or is the PSU still able to provide power to the USB ports?

**Confused** · 05-20-2004, 07:47 AM

I believe that the ITPS will cut off all power, but i have never used one (got an Opus) so can't say for sure.

Garry

**jusatry** · 05-20-2004, 03:33 PM

no piston - i dont know about the itps, but the muchas cuts power completley (in case windows hangs during shutdown). I would assume thats what the ITPS does too. Search for threads by MikeH - he knows alot about this stuff, and im pretty sure he uses an ITPS with his M10000. check his sig for info on his site. also - im still selling that 20 gig laptop HDD, but based on your diagram, it looks like that may not be enough

Anyway, if you want it ill cut you a deal cause your internet connection is so fast

Confused: Great avatar!!

**NoPistonPC** · 05-20-2004, 04:49 PM

Thanks, I'll do some more research. Yeah, I think 20GB will be too small for all my music and movies, but thanks for discount offer!

**Bravellir** · 05-20-2004, 05:15 PM

hi,

I’m also trying to find out if anyone successfully booted from a USB external drive.

Need to move the HDD to the front of the pickup. The vibration on the back is killing my hdds.