I have a USRobotics internal PCI hardware modem that works with DOS but not with EPPPD, only with LSPPP. IRQ is 11, base address is 0xd400, which I determined by running a PCI program by Ralf Brown. This same information also shows in Linux in /proc/pci . Sometimes an ISP or more distant server will change things a little, and DOS software that previously worked no longer works. Previously I let LSPPP dial, but when there was a portmaster change that I could hear in the modem after dialing, LSPPP was no longer able to make the IP connection, but then I let chat0.exe (from DOSPPPD package) dial, and LSPPP then was successful in connecting. Then it is also possible to be unable to connect for some time due to bug or downtime at the ISP end.
I don't think DOS would be able to dial at all with a Winmodem, and I don't think DOS or any other OS would be able to dial if either the IRQ and/or base address were wrong. I think my init string is AT&F1S6=7 and dial string is ATDTW followed by telephone number. So it waits up to 7 seconds for a dial tone if dial tone is not immediate.
