Start up restarts

Mac Format - - GENIUS TIPS -

QWhen start­ing or wak­ing my iMac Mid 2011 run­ning 10.11.6 often spon­ta­neously restarts sev­eral times be­fore work­ing, even in Safe mode. I’ve re­seated and tested me­mory. There are crash re­ports re­fer­ring to GPU re­sets. Is the graph­ics card dy­ing? by Kris Lee

ATh­ese restarts are al­most cer­tainly caused by re­peated ker­nel pan­ics, most prob­a­bly re­flect­ing a fail­ing graph­ics card, but they could re­sult from El Cap­i­tan’s fragility.

Run Ap­ple Hard­ware Test (AHT, or Di­ag­nos­tics on re­cent mod­els) first. Shut down and dis­con­nect all ex­ter­nal de­vices apart from wired key­board and mouse and any wired Eth­er­net con­nec­tion. Start up, and im­me­di­ately press and hold D un­til the AHT icon ap­pears. Se­lect lan­guage, click the right ar­row, be­gin the test. Ini­tially, run nor­mal rather than ex­tended test­ing. If you can’t get your mouse to work, use the cur­sor and ® . Some­times AHT or Di­ag­nos­tics don’t de­tect graph­ics card faults, which should return an er­ror code start­ing with VFD, typ­i­cally VFD006. More ex­ten­sive hard­ware di­ag­nos­tics from your lo­cal Ge­nius Bar may be needed.

If there’s def­i­nitely no hard­ware fault, browse your logs fol­low­ing start­ing up. For El Cap­i­tan, check out bit.ly/elec­tri­clight_read­in­glogs. Con­sider up­grad­ing to macOS Sierra, which is more stable in this re­spect, and bet­ter sup­ported.

If you can’t use a wired mouse or track­pad, nav­i­gate di­ag­nos­tic test­ing us­ing the cur­sor and ® key of a wired key­board.

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