08-25-2010 11:09 PM
In the past, I've used 80G SATA and 160G PATA drives (Seagate, if I recall) in USB enclosures based
on the JMicron JM20337 bridge chip. No problems previously.
Just bought a new ST3500418AS and another such enclosure and have a major problem - all sector write
operations seem to silently fail in DOS (using the Panasonic ASPI/USB driver + Adaptec ASPIDISK) and in
Windows 98SE (using the JMicron drivers). However, in Vista, it works fine. WHY?!!!
BTW, I'm trying simply to create a FAT32 partition of less than 64G for maximum O/S compatibility (but prefer
not to be limited to the artificial 32G limit of Vista). Making use of more than 64G is a lower priority.
I've tried writing sector 0, but it reads back unchanged. Thought this was some sort of protection for the MBR,
but doing the same test on sector 666 produced the same result. Tried with various tools in DOS and W98SE.
Solved! Go to Solution.
08-27-2010 01:13 AM
08-28-2010 07:17 PM
Your problem may be due to a bug in the JM20337. Search the web for : jm20337-read-data-corruption-solution . Check for a resistor, often labelled R15, between pin 34 and ground. If it's loaded, remove it. That's for a silent read error that may occur every once in a few GB. For my enclosure, the resistor is called R1 and it's not loaded, so I've not experienced this particular problem.
My problem is with silent write failures, on EVERY sector write operation. Read operations seem fine, the drive is detected, assigned a drive letter, and seems to read just fine.
However, I've not had this problem with previous drives (80G SATA and 160G PATA) with the JM20337. The problem is specific to this new 500G SATA (ST350041 8AS) drive. Something's different with it, perhaps a timing problem with write operations, perhaps some sort of write=protection mode, I don't know. I hope someone here can shed some light on this issue.
08-31-2010 04:49 AM
09-21-2010 07:33 PM
I wish someone from Seagate would have shed some light on this problem by now.
Anyway, some new information :
It occured to me that the Vista laptop (which worked OK with this USB enclosure and hard drive) and the W98/DOS PC did not operate the same speed/version of USB.
So I tried the USBASPI.SYS and DI1000DD.SYS drivers (I usually prefer ASPIDISK.SYS, but DI1000DD.SYS provides an INT13 interface, which can be handy sometimes) on the laptop. Sure enough, in EHCI mode (USB 2.0), everything worked fine, in UHCI mode (USB 1.1), the silent write failure problem was back!
So the apparent difference in behaviour wasn't due to the O/S or drivers after all. The problem is that the ST3500418AS and JM20337 combination fails on write in UHCI (USB 1.1) mode!
Why? What's different in this 500G 7200.12 drive compared to the 80G 7200.10 drive that works just fine with the JM20337? And why should the lower USB speed have problems, yet the higher speed be OK?
11-17-2010 12:00 AM
@ fzabkar : Unfortunately, my W98SE PC only has UHCI ports, so I can't test EHCI. However, I have booted my Vista laptop in DOS and tested that in both UHCI and EHCI modes.
Anyway, today I have news from JMicron, who have been very, very helpful in investigating this problem with me. It turns out the problem is a PCB layout problem with my new USB enclosure (Forcom / Channel+ model 35HDUPS). The USB and SATA signal traces are too close together and the USB is corrupting the SATA. It only affects UHCI mode because "USB1.1 signals swing from 0 to 3.3V while USB2.0 signals swing from -0.4 to 0.4V". Mystery solved!
JMicron have notified Forcom of the problem, so hopefully there won't be this problem in the future. I'm really impressed with the efforts JMicron made to resolve this problem.