Memory Errors; Usb Features - Dell Precision 3430 Small Form Factor Service Manual

The key notch on a DDR4 module is in a different location from the key notch on a DDR3 module. Both notches are on the insertion edge
but the notch location on the DDR4 is slightly different, to prevent the module from being installed into an incompatible board or platform.
Figure 1. Notch difference
Increased thickness
DDR4 modules are slightly thicker than DDR3, to accommodate more signal layers.
Figure 2. Thickness difference
Curved edge
DDR4 modules feature a curved edge to help with insertion and alleviate stress on the PCB during memory installation.
Figure 3. Curved edge

Memory Errors

Memory errors on the system display the new ON-FLASH-FLASH or ON-FLASH-ON failure code. If all memory fails, the LCD does not
turn on. Troubleshoot for possible memory failure by trying known good memory modules in the memory connectors on the bottom of the
system or under the keyboard, as in some portable systems.

USB features

Universal Serial Bus, or USB, was introduced in 1996. It dramatically simplified the connection between host computers and peripheral
devices like mice, keyboards, external drivers, and printers.
Let's take a quick look on the USB evolution referencing to the table below.
Technology and components 9