If you want the absolute smallest form factor 128MB, then you need the following PCB.
http://www.ebay.co.uk/itm/128MB-Low-profile-LP-EDO-SIMM-non-Parity-72p-Memory-RAM-72pin-32x32-60ns-TSOP-/121743177271?hash=item1c58757637:g:hnEAAOxyhTFSTeYGThe above PCB is what I used to build the worlds fastest EDO memory 28ns, using TSOP chips. I bought 64Mb version (cheaper), then filled in the other side for 128Mb.
Test has shown some listing of 50ns EDO memory on Ebay, do not operate at 50ns, even if the marking on the chip say 50ns.
You will get better success 50ns EDO, if chips were NEC, next is Micron, but I find to many faults here to be class as 50ns with Micron chips.
It seem what they are doing is off-loading as many EDO memory chips/Simms, without checking their speed.
Micron chips is what I started with, allowing 66Mhz bus low latency on Blizzard PPC, then moved to NEC with better result.
There is nothing wrong with Micron chips, it can give the same result as NEC, if it is properly checked, but NEC chips are more likely to operate at 50ns regardless if it is checked, this is what I found, but NEC chips are also not guaranteed to work at correct speed, as faults was also found with this make of chip.
I no longer use Micron or NEC chips for the ultimate 128Mb Simm, and I could have built 25ns EDO Simm, and test was showing 24ns (even quicker), but it was too expensive to complete this project. This is why no one will ever get near this Blizzard card
http://www.amiga.org/gallery/index.php?n=3692DDR1 project is coming to an end, expecting to see PC-3500+ CL1.5 4GB Quad kit/Dual Channel Ultra Low Latency DDR1 with "Enhanced Bandwidth" built into the SPD, next project SDRAM.