Seagate 7200.11 Shows 0GB in BIOS — BSY Bug Fix

You power on the machine and the BIOS POST screen lists your Seagate Barracuda — model, serial, everything. But when you get into the BIOS drive table, the capacity column says 0GB. Disk Management shows the drive as "Not Initialized" or doesn't show it at all. That's the BSY bug.

This hits ST3500320AS, ST1000340AS, ST3750330AS, and the rest of the 7200.11 family made between roughly late 2008 and early 2009. It usually strikes after a power loss, a hard shutdown, or even a firmware update gone sideways. The drive spins up fine. It just never leaves the busy state it enters on boot.

What's actually happening

Every Seagate drive has a small translation layer in firmware that maps logical block addresses (LBAs) to physical sectors. That translator reads its config from a reserved area on the platters during spin-up. On the 7200.11, a bug in the SD1A and earlier firmware means that if the translator gets interrupted — power cut, unexpected reset, certain SMART events — the drive initializes to a default 0GB translation table and locks itself in BSY.

BSY is a status bit the drive sets while it's busy. Normally it clears in a few seconds. On a bugged 7200.11, it never clears. The BIOS can still query the identify device command and get a model string back, which is why you see the drive listed. But any attempt to read capacity returns zero because the translator has no valid geometry loaded.

Seagate acknowledged this and released firmware SD1A, then later CC1H, CC1G, and others. If your drive is running AD14, SD13, SD14, SD15, SD81, or SV11, you're exposed.

The fix: unlock BSY over the diagnostic serial port

You need to short the drive's read-channel to force it into a boot mode where you can send terminal commands. A Nokia CA-42 cable works as a cheap USB-to-TTL adapter, and it's what most people used back when this bug was news. You can also use any 3.3V USB-serial adapter if you're careful.

1. Get the tools. A Nokia CA-42 or DKU-5 cable (the CA-42 is more reliable), a Torx T6 driver, a SATA power source or a USB-to-SATA power adapter, and PuTTY or a similar terminal app on Windows.
2. Strip the CA-42 cable. Cut the phone-end connector off, peel back the shield, and identify the three wires: usually red (RX), blue or white (TX), and black or green (GND). The colors vary by clone. Test with a multimeter or look up your specific CA-42 revision.
3. Connect to the drive's diagnostic port. Remove the PCB from the drive (four T6 screws). The diagnostic header is a 4-pin pad near the motor connector labeled TX, RX, GND (and sometimes VCC — leave VCC alone). Solder or use pogo pins: drive TX → cable RX, drive RX → cable TX, drive GND → cable GND.
4. Don't fully reattach the PCB yet. You need to short two specific read-channel pins on the motor side of the PCB to force the drive into safe mode. On most 7200.11 PCBs, that's the two pins nearest the spindle motor connector on the head side. Insulate the PCB from the chassis with a piece of paper so nothing shorts to the metal housing.
5. Power on with the terminal open. Set PuTTY to the COM port of the CA-42 at 38400 baud, 8N1. Power the drive. You'll see the drive's boot log. If BSY is stuck, you'll get a spinning prompt or silence.
6. Send the safe-mode sequence. Type each line followed by Enter, waiting a beat between them:

   /2
   Z
   U
   /1
   N1
   /1
   Z
   U
   /2
   Z
   U
   /t
   F
   

   The Z command spins down the drive. U resets the translator. F repairs the translator when it's corrupt. If F returns an error, try the sequence again — sometimes it takes two passes.
7. Power cycle. After the F command completes without error, remove power, wait 10 seconds, reconnect the drive normally to SATA. It should now report its full capacity.
8. Flash the firmware immediately. Do not skip this. Download the correct ISO from Seagate's archive (search "Seagate 7200.11 firmware SD1A") and flash it before you trust any data to the drive. If you don't flash, the BSY bug will come back the next time the drive loses power unexpectedly.

If the drive still won't come out of BSY

Three things to check:

• Read-channel pins. On some PCB revisions the short pins are on the opposite side of the motor connector. Look for the pair that, when shorted, causes the drive to spin up but not seek.
• Cable wiring. Swap TX and RX. A surprising number of CA-42 clones are labeled wrong, and a silent terminal often means you've got them reversed.
• Firmware level. If the drive is on CC1H or later, the F command might not help and you're looking at translator corruption from a different cause — in that case, the platters are probably intact but the service area needs rebuilding with a tool like PC-3000. That's a paid shop job, not a DIY fix.

One more thing. If the data on that drive matters, stop poking at it and call a recovery lab. The BSY fix is safe when it works, but every failed attempt writes to the service area. Good luck.