MiSTer FPGA Forum

Has anyone used the AS4C32M16SB-7TCN chips to make the 128MB SDRAM boards?

I looked at the specs and they looked to me like they would be an appropriate substitution, however I'm having issues with them. They test just fine in memtest - I can run them overnight for 8+ hours and they operate at 140MHz without any errors. But when I actually play a core sooner or later (usually 30 minutes or less) the core freezes or has graphical glitches of some kind.

Is this chip just not good enough? Why does memtest pass yet the RAM is no good?

Thanks in advance for any help.

The datasheet, if it helps:

https://www.alliancememory.com/wp-conte ... 202016.pdf

The AS4C32M16SB-7TCN modules work without issues.

A few tips firstly double check your soldering for each chips pin leg with magnifying glass / microscope. If its passing memtest but not in cores also check soldering on the inverter. If your soldering is good make sure the module has had a good clean to remove any flux residue.

Secondly are you sure you have purchased genuine Alliance chips, as remarked chips exist. Where did you purchase them from?

Thanks for the reply Nat. I have looked at everything under a microscope and I didn't see any issues. I will give them another inspection though just to double check.

I saw some comments on the old Atariage forum about making sure they're very clean so I gave them another scrub last night. No change. Matthew there's some stubborn flux behind the pins) under the chip that's not getting cleaned up? I can soak them in iso to see if that helps.

I purchased them from DigiKey. My assumption is they should be a reliable source for genuine parts?

jdsilva wrote: ↑Fri Nov 13, 2020 3:03 pm I purchased them from DigiKey. My assumption is they should be a reliable source for genuine parts?

They are one of my suppliers of choice for the Alliance memory modules unless buying direct, I have never had an issue with the authenticity of components supplied by Digikey.

Nat wrote: ↑Fri Nov 13, 2020 3:17 pm They are one of my suppliers of choice for the Alliance memory modules unless buying direct, I have never had an issue with the authenticity of components supplied by Digikey.

That's what I thought. OK, I'll go back and re-examine everything again. Appreciate the input Nat!