The SE/30 will take 512K, 1MB, 4MB, 8MB and some 16MB 30-pin SIMMs, installed in lots of 4. There are eight SIMM slots in the machine meaning there are two banks of RAM, named A and B. This means the machine can be upgraded to a whopping 128MB total!
1MB SIMMs are quite easy to find (and cheap) but larger sizes are getting a little scarce now. If you wish to be adventurous with your SE/30 I would suggest looking for some of the larger chips as the extra RAM will give a noticable increase in performance. You'll need to install the Mode32 extension to address more than 8MB as the SE/30 has a 32-bit "dirty" ROM. My SE/30 runs quite happily on 8MB, (8 x 1MB SIMMs), which is adaquate for retro gaming and some older apps.
1MB SIMMs are quite easy to find (and cheap) but larger sizes are getting a little scarce now. If you wish to be adventurous with your SE/30 I would suggest looking for some of the larger chips as the extra RAM will give a noticable increase in performance. You'll need to install the Mode32 extension to address more than 8MB as the SE/30 has a 32-bit "dirty" ROM. My SE/30 runs quite happily on 8MB, (8 x 1MB SIMMs), which is adaquate for retro gaming and some older apps.