With SIMMs, the only thing I can suggest is to try to find a datasheet for the part number on the RAM chips. If you manage to find a datasheet, it should tell you if they're EDO.
72pin SIMMs have their speed, and I think maybe their size, coded using a series of on/off switches on some of the pins. They will have some small resistors which are used as jumpers to put certain pins either at 5v or ground. This binary sequence tells the motherboard what the access time is supposed to be. I think the size is also coded this way, but I'm not sure about that.
So in theory, by looking close at how it's jumpered, and with a pinout of where +5v and GND come from, it would be possible to figure out what the module is trying to be.
At some point I think they ran out of "bits" and had to start reusing old, previously defined sequences. So for example, a particular on/off sequence might be interpreted as 2 different capacities or 2 different speeds, or whatever. I don't remember the specifics, but I read something about this a few years ago. At the time, I was trying to figure out what SIMMs would work in an HP Laserjet, because it had some particular requirements to recognize them.
That said, I don't have a link for what the coding sequences are, but the info must be out there somewhere. I looked in my files but I must not have saved it.
Starting with DIMMs, they started programming the information into a serial EEPROM, which allowed the information to get a lot more detailed and complicated.
Many times the part number on the chips will give a clue of their speed. However, many times the SPD program is set slower than what the chips are rated for, so this isn't a reliable indicator of how the modules will be detected. That's especially common with PC100 modules that actually had PC133 capable chips on them.
I don't know any way to identify EDO vs SDRAM DIMMs except to find a chip datasheet.
You can pretty easily tell if DIMMs are unbuffered vs registered by looking for the small buffering chips sitting in between the edge connector and the RAM chips. Unbuffered memory won't have those, registered/buffered memory will.
You can tell if they're ECC by counting the number of RAM chips. Each logical "row" of a non-ECC module feeds a 64-bit data bus, so it will have 4, 8, or 16 chips. Each logical "row" of an ECC module has to feed a 72-bit data bus, so this will result in 9, 18, or sometimes 36 chips being installed.
I don't know if this works the same on SIMMs though.
