Voice V.90 ISA modems. Hours on the internet and modulation is rock solid. Both were well worth the extra money. Even my HP USB modem cannot modulate signals as well as the Python modems. I have the internal ISA as well - same model no.
Connectivity is rock solid, all the time.
Compatibility is perfect. This modem is very consistent at getting high connection speeds and never has random disconnections from my internet server. My connections speeds are always at 46666 or 45333, and playing games online is great for a dialup connection. Great modem for anyone that can't afford high speed internet connections. I have the ISA voice 5685 modem by the way.