notes of a System/Next™ distribution or because your update somehow failed (for example lost power while updating). The regular core (for both Issue 2 and Issue 4 mainboards) is contained within a file named **TBBLUE.TBU**. In order to update the flash rom you need to place it on the root folder of your SD Card together with the file containing the firmware: **TBBLUE.FW**. Both of these files need to be present for a successful update. Regular operations, however , require only the **TBBLUE.FW** file to be present at all times in the root of your System/Next™ distribution. Regardless of the update method you need to have them both so make a note for that. Just placing a TBBLUE.TBU file on the root of the card won't update the core; there are additional steps you need to take. Let's examine the two update options below. ### Regular Core update The regular core update method is quite easy. After you've made sure you have the **TBBLUE.FW** and **TBBLUE.TBU** on the root folder of your card, press and hold **U** on your keyboard and while doing that, *long*[^p298-3] press the **RESET** button. Do not release the **U** key until you see the following screen (Note that if you have a KS1 ZX Spectrum Next, an N-Go computer or a KS1 dev board your Board Id will say **ZX Next Issue 2**):  ``` ZX Spectrum Next Configuration Updater Board Id ZX Next Issue 4 Slot 01 Version 3.02.00 Do you want to upgrade? (y/n)y Verifying checksum \ ``` *Fig. 50 – Core update screen* Release **U** and then press **Y**. The updater will first calculate the checksum of the core bistream; once it finds everything is OK, it will start upgrading; first erasing the Flash ROM and then, once done successfully, writing the core bistream from **TBBLUE.TBU** in its place. Once the procedure has finished, you will receive an: **Updated! Turn the power off and on.** message. Remove the power and if using an HDMI display, the display cable as well. Wait a few moments and then reconnect everything. The machine should restart with the new core. ### AB Core update If the process failed somehow; or if you're so instructed by the accompanying notes of your **System/Next™** distribution, you can do an *AB core update* to remedy the situation. This is a bit more complicated and it's made so as to avoid entering this mode by mistake. To enter AB core update; you will need to power off your machine, then press and hold the **NMI** and **Drive** buttons together (on the side of the computer) and while doing that reat- [^p298-3]: More than 1 second