Macbook Pro 13 A1278 820-2530 with ddr problem.

Beeps on boot with only one (or two) ddr in any of the slots, but works properly disconnecting both battery and magsafe, wait for 10 seconds, and power it on again. (then it can works for hours with no problems)

When reboots or shutdown and then press power button, it starts beeping again, it only works again if disconnect battery and magsafe.

I know it is a weird problem, but perhaps someone knows how to solve.

Thanks.

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[size=85]Posted after 2 hours 17 minutes 20 seconds:[/size]
I have performed a smc reset and a pram reset and it behaves the same.

When it is working, doing a smc reset, (press shift, option, and control keys, and press the power button) it shutdowns, and beeps when power-on again.

I've tested it with all kind of ddr3 modules of course.

Thanks for your comments or help.

IMHO, MCP79 dies, or You are using incorrect dram type, for example ddr3-1600 instead of 1333 or 1066.
When You discharge RTC - it is all right, crashed data is cleared and readed one more time,
but when RTC CMOS data is damaged on reboot/reset - it can't initialize dram controller by dram settings in CMOS.

Shooter75
Thanks for your answer, the memory type it has is ddr3-1066. (2x1gB)


Yes, it is very likely MCP79 has died, the weird thing is that when it works, it is all ok.

I'm thinking in make a circuit for clear the rtc data with a push-button or something. (customer do not want to spend too much money)

Can You make measures at pins 1, 126, 203, 204 at DDR3 socket in moment, when it beeps?
Do You have 0,75v ?

Shooter75
Thanks for your help, I forgot to mention that the main problem was bios chip, it was erased by someone. (perhaps the one that sell it, and also the hdd have no data)

I had reprogrammed the bios with a dump I had downloaded many time ago, and didn't know if it was ok.

Seems that the problem was data corruption on this dump.

I have reprogrammed with a new dump, and the problem is completely solved.

It is the first time that a corrupted bios behaves this way to me. (but it was the more likely to be the culprit)

Thanks to you for your help.

Cheers.