The timing was part of it, but the other part really was just that NeoGeo games demanded a large amount of memory that just made for too expensive of a system. The slow CD-ROM certainly hurt too. If it could have had a faster CD-ROM and a RAM expansion capability it might have lasted longer in Japan but I think outside Japan it probably was doomed to fail still. Just unfortunately too expensive to bring the NeoGeo home. The FDS uses IRQs for two things. Disk Access and then also with the IRQ timer I mentioned that is typically used for raster effects. Besides that the FDS had it's extra sound capabilities. Unfortunately not unlike the NeoGeo CD it also had too little memory and no way to expand it. With only 32KB of Program RAM and 8KB of Character RAM that looked pretty poor compared to cartridges containing 128KB or more of ROM. But before ROM prices got cheaper it looked great having 32KB/8KB of RAM to load with data off a cheap 64k per side disk. That's one reason I think the Saturn was awesome with it's RAM expansion cartridges. The arcade ports that use them are excellent and make the Playstation versions of the same games look terrible. The Playstation needed such an expansion too. I'm not sure if the Parallel I/O on the PS could allow for full speed memory to essentially add to the Main Program memory to expand beyond 2 megabytes of RAM. If it could have been done it's a real shame they didn't do it. Play Metal Slug or Metal Slug X on the PS and cry at the poor animation quality.