This prototype build of the XO-1 laptop ran from June 20-25, 2007, and was the final chance to fix hardware and mechanical problems that were detected in the Beta Test 3 build of the XO. Over 2000 units were built. Additional information is available at BTest-4 Release Notes.
Texture was added to the upper handle bar, the hinge tilt was increased by 7 degrees, the hinge "squeak" was eliminated, the rabbit ears click in place when put in the "down" position", the slight camera vignetting seen in B3 was eliminated, and minor modifications were made to the motherboard.
- Rubber antenna "ears"
- Dimples only on battery cover; no texturing of bumpers and other surfaces
- Labels under battery include "B4 - TEST SAMPLE",
- The hinge cover is now white, not green
 Software Support
Beta Test 4 laptops work with current software releases.
They may experience hardware problems with extensive suspend/resume or low battery, and the software prevents suspend/resume on B4's.
- There may be occasional crashes (possibly made worse by suspend/resume) when the battery is running low. Above 25% of capacity, or plugged into a power adapter, you should be OK (Trac #1835)
- There may be times when the WLAN (USB) hangs (possibly made worse by suspend/resume) (Trac #1752, #4476)
- Power cycling the DCON is liable to crash the laptop. This power cycling will occasionally happen in response to a DCON bug triggered by suspend/resume (#4479);
- Rare crashes may be caused by other sources during suspend/resume (Camera, SD card, clock settling time), some units may be more sensitive than others (#1835)