Remote sync speed=.....

09-29-03, 10:33 PM

I have noticed when installing apps with active sync on my ax, that it is faster to go over my network using a cf wifi card than using the cradle. Anyone else notice this?

AximJoe · 09-29-03, 10:42 PM

Yeah, I agree. I don't know what the speed of USB is, but I don't think it's near 11Mbs.

MurMan · 09-30-03, 02:03 AM

The Ax is a USB 1.1 device. The USB 1.1 spec. defines two speeds: a low-speed at 1.5 Mbps and a full-speed at 12 Mbps.

Based on file-transfer times, it seems to me that the Ax operates at the low speed.

Howard2k · 09-30-03, 07:00 AM

Try doing a backup in the cradle vs wifi... Then you'll REALLY see the difference.

09-30-03, 08:00 AM

Yeah its amazing the speed differance, plus I dont have to take the ax out of its piel frama case to sync it

Roner · 09-30-03, 04:46 PM

As far as I know, and I could be mistaken, the Axim is serial-port compatible and not USB-compatible. And that means a max speed of 115kbps. Long live Wi-Fi syncs.

Handy · 09-30-03, 05:03 PM

The sync cable connects to the USB port on your desktop, so it's using USB, not a serial port when you sync. I think the Axim has both USB and old-style serial connections. I don't think the USB is limited to 115kbps.

Howard2k · 09-30-03, 05:51 PM

Everything I've heard goes along with what Roner is saying... Could be wrong though.

MurMan · 10-02-03, 02:53 AM

I've been very curious about the interface, so I installed a trial version USB Monitor program from www.hhdsoftware.com/download/usbmon.exe Here's a summary of what I found:

The Ax is a USB 1.0 device that runs at full speed (that's the 12 Mbps rate.) It connects to ActiveSync using 3 end points.

I monitored a sync session and counted packets during one second that looked typical. During this period, it completed 110 packets that transferred a total of 273,000 bytes. I don't know what the USB protocol efficiency is, but I know USB is polled by the host, so it's much less than the 12Mbps line data rate.

Two observations:
1. There was a LOT more data transferred for a re-sync than I had expected. (Nothing on the host or Ax had changed.)
2. I can't explain why Howard sees much faster sync times using WiFi. Is WiFi that much faster than a 12Mbps USB connection or is the Ax implementation of USB slow?

Howard2k · 10-02-03, 08:14 AM

I don't know enough about USB but if it's polling the end devices then I would expect it to be more efficient than wifi with only two active devices (PC and Axim).

I would imagine that the USB Host would have to know which devices are active and then poll them. Only one device active means only poll one device. Depends how the polling interval works of course.

273,000 bytes is 2Mb/s. So that's higher than I expected to be honest. The Axim is hardly a high horsepower device and over wifi won't do much more than 2Mb/s either from what I've seen...

From a order of magnitude perspective, doing a backup in the cradle would take me maybe 25 minutes, compared to 4-5 minutes via wifi. That's not scientific, just my recollection.