> Hm, on the lower row of pads I find damage that looks very > similiar, just not as extreme though. I don't see anything like it? At many places the metal is cracked and darkened, but near A7 it is totally black and not cracked. But who knows :-) > Also when you look at the layer 'counter', you can see what looks > like 3 cracks in the die. Could just be the lighting and the > passivation layer though. There are many more cracks and quite some chipping, but it's harder to see on places where there is metal etc. underneath. >> The driver structure for P5 is >> also missing; for the 8500 and 8502, this will have to be different. The drivers / latches for D and P are, top to bottom: 0 1 2 3 4 6 7 5, where that last one doesn't have the P stuff. The lines coming from the core are swapped, and the lines going to the pads as well; it looks completely obvious that this is just a simple modification of the 8500/8502, which means that one is earlier. > Are you able to determine the logic connected to the GATE_IN signal? Probably, but I haven't done it yet, this photo is pretty hard to read. > Well, remember the 2 major differences between the 6502 and the > later variants. First you have the AEC signal allowing you to > tristate the address bus and some signals. That means changes to > their drivers and at least one control signal to all of them. > Second you have the I/O-Port residing on $0000 and $0001. That > means you have to route all address signals to the access decoder > for the port register and all data signals to the port itself. That > should explain at least some of the extra traces near the pads. Not really. For the AEC and "this is address 0/1" signals you need only two wires total. You do not route all address signals to a decoder; instead, you use a decentralised decoder: what you need is just a NOR of the address pins A1..A15, you split that NOR gate so that the pulldown for every address bit is located with its driver. The 850x actually does that. These additions can easily be made to a 6502 to create a 6510, without adding a whole wide ring of stuff around it all, except obviously for the P port stuff itself. The 850x is different of course, because the pad drivers have to be a lot bigger relatively. So I'd still like to see what things look like on the 6510 :-) Segher Message was sent through the cbm-hackers mailing listReceived on 2012-07-18 14:00:23
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