Gary (Amiga 500)

the gary chip provides bus traffic control signals for the address and data bus it was a consolidation of a large amount of discrete 74 series components and pals originally in earlier amiga models like the a1000 basically, it is needed for the 68k to even read and load the bios or access the rom, so is a core chip needed for the most basic operations to work signal operation during normal operation, below is a basic description of how every single pin should be operating if probing using an oscilloscope these tests are done in the minimum boot configuration (so with ram, cia, paula and denise removed) !vpa pulsing !oel 5v !oeb pulsing during boot, then 5v !kbreset 5v !mtr 0v dkwe 0v !dkwd 0v (5v if paula installed) !lds pulsing !uds pulsing r/w pulsing !as pulsing !bgack 5v !blit pulsing !sel 0v !regen pulse during boot, then 5v !bliss pulse during boot, then 5v !ramen 5v !r0men pulsing !clkrd 5v !clkwr 5v mtrx 0v mtron 0v dkwdb 0v !dkwe 5v !dtack pulsing !halt 5v !reset 5v a23 high a22 pulses during boot then high a21 pulses during boot then high a19 a20 high a18 a17 pulsing !exram 5v xrdy 5v 0vl 5v !0vr 5v cck 3 54mhz cckq 3 54mhz !cdac 7mhz !latch 3 54mhz