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Re: diagrom showing 0 fastmem on new board
Posted: 25 Nov 2019 07:45
by terriblefire
I’ve had this conversation 100 times now with various people. If the ram isn’t working either the solder joints are bad or your parts are screwed. It’s usually the bad joints. Many times I’ve seen the legs not even making contact with the board. Are you using a microscope?
Do any data bits retain data or do they all fail?
Try going to 0x200000 and type stuff in and see what is retained
Re: diagrom showing 0 fastmem on new board
Posted: 25 Nov 2019 11:30
by Homer79
I've seen this many times if you get the cheap Alliance memory from ebay
It simply just does not work or you get lots of memory errors.
Re: diagrom showing 0 fastmem on new board
Posted: 25 Nov 2019 12:09
by oggie
yes. all parts are from digikey, and the board was from the link on github (dirtypcbs I think).
Re: diagrom showing 0 fastmem on new board
Posted: 25 Nov 2019 12:19
by terriblefire
oggie wrote: 25 Nov 2019 12:09
yes. all parts are from digikey, and the board was from the link on github (dirtypcbs I think).
Then it’s solder joints. You just haven’t found the issue yet.
Re: diagrom showing 0 fastmem on new board
Posted: 25 Nov 2019 12:53
by oggie
I have cheap lcd scope from aliexpress which works ok . I'm saving up for a better scope.
So If I'm able to get at least one memory chip soldered correct, I should have 1mb at least right? So If I can focus on the chip closest the cpld and it's finally working, I should be able to at least have 0x200000 to 0x300000 as usable correct?
Or do I have to have all 4 correct to get any usable memory?
If I put in data at 0x200000 it is not retained.
Re: diagrom showing 0 fastmem on new board
Posted: 25 Nov 2019 13:00
by terriblefire
oggie wrote: 25 Nov 2019 12:53
I have cheap lcd scope from aliexpress which works ok . I'm saving up for a better scope.
So If I'm able to get at least one memory chip soldered correct, I should have 1mb at least right? So If I can focus on the chip closest the cpld and it's finally working, I should be able to at least have 0x200000 to 0x300000 as usable correct?
Or do I have to have all 4 correct to get any usable memory?
If I put in data at 0x200000 it is not retained.
Each chip strides 8 bits of a 32bit word. If nothing is retained it may be address pins not connected or shorted at the Ram CPLD. Or it could be dead RAM.
Re: diagrom showing 0 fastmem on new board
Posted: 25 Nov 2019 13:02
by oggie
Are these ram chips know to die easily? How would you even know if they were bad besides swapping them out?
Re: diagrom showing 0 fastmem on new board
Posted: 25 Nov 2019 15:47
by arkadiusz.makarenko
Could you do some high Res picture of the board?
I check for bad joins by taking needle and gently tapping each leg (under microscope). I was VERY supprised that I found more than half a dozen legs not soldered property, even if they did look ok from above under cheap usb microscope.
Re: diagrom showing 0 fastmem on new board
Posted: 25 Nov 2019 20:03
by terriblefire
oggie wrote: 25 Nov 2019 13:02
Are these ram chips know to die easily? How would you even know if they were bad besides swapping them out?
I've never killed a static ram chip in all my time doing this. More likely bad joints.
Re: diagrom showing 0 fastmem on new board
Posted: 25 Nov 2019 20:41
by terriblefire
oggie wrote: 25 Nov 2019 00:26
ok. I ran autoconfig and got this :
https://photos.app.goo.gl/akyREk8uXiCKHf3C8
So based on your statement, that means it's the address path? the address path from the cpld to the ram chips?
I checked continuity from the cpld to the ram chips and they all seem to be connected.
OK i hadnt looked at this pic before. My bad. What firmware are you using? Because you should see it assign a device. Looks to me like the RAM CPLD doesnt have all the signals it needs to know a cycle is taking place.