SIMM memory module

[PerOs1968]

I am hopeful that someone can clarify this for me. I have a bunch of SIMM's and tried to figure out what exactly the capacity of these are. I first thought that each of the 8 components on the memory module was 256 KB of RAM, which would make the whole memory module 2 MB, but it seems that the whole module is actually 256 KB, is that right? And how to make the calculation for this?

And what is the difference between the ones with and without components soldered on the back of the memory module?

I have also attached a PDF document of the Siemens HYB 41256-x DRAM component in this post

HYB41256-12.pdf

[Guest Generallee]

By the serial number It's 256kb total. As for the components on the back, god knows since these things are so prehistoric

[ProximaOfZeal]

The marking on the chip describes capacity in kBITS, 8 bits make up a byte, therefore 8 chips are 256kbit x 8 = 256kBytes. The stuff on the back are just decoupling capacitors between the chips' +/- power pins, it helps the voltage smoothness improving working conditions for the chips. As to why one module has them and the other not - or actually both have them, it's just that one of the modules has caps for the whole power rail rather than each chip separately - I guess it comes down to cutting costs.

[PerOs1968]

58 minutes ago, Generallee said:

By the serial number It's 256kb total. As for the components on the back, god knows since these things are so prehistoric

Thanks for the fast response! And for the information!

[PerOs1968]

51 minutes ago, ProximaOfZeal said:

The marking on the chip describes capacity in kBITS, 8 bits make up a byte, therefore 8 chips are 256kbit x 8 = 256kBytes. The stuff on the back are just decoupling capacitors between the chips' +/- power pins, it helps the voltage smoothness improving working conditions for the chips. As to why one module has them and the other not - or actually both have them, it's just that one of the modules has caps for the whole power rail rather than each chip separately - I guess it comes down to cutting costs.

The internet is just wonderful and so many good people with so much knowledge! Thanks for the fast response och the detailed information! Now it makes sense and I have learned something new - just lovely!