>The CPU was a CMOS version of the 8086, compatible with the IBM PC's 8088 except it ran slightly slower, at 4.0 MHz instead of the standard 4.77 MHz.
>Unlike the Portable PC, the DG-1 laptop could not take regular PC/XT expansion cards.
>RS232 serial ports were built-in, but the CMOS (low battery consumption) serial I-O chip available at design time, a CMOS version of the Intel 8251, was register incompatible with the 8250 serial IC standard for the IBM PC. As a result, software written for the PC serial ports would not run correctly. This required the use of software written using the relatively slower and less flexible BIOS interrupt call (014h), or software written exclusively for the DG-1.
>The CPU was a CMOS version of the 8086, compatible with the IBM PC's 8088 except it ran slightly slower, at 4.0 MHz instead of the standard 4.77 MHz.
>Unlike the Portable PC, the DG-1 laptop could not take regular PC/XT expansion cards.
>RS232 serial ports were built-in, but the CMOS (low battery consumption) serial I-O chip available at design time, a CMOS version of the Intel 8251, was register incompatible with the 8250 serial IC standard for the IBM PC. As a result, software written for the PC serial ports would not run correctly. This required the use of software written using the relatively slower and less flexible BIOS interrupt call (014h), or software written exclusively for the DG-1.
https://en.wikipedia.org/wiki/Data_General-One#Drawbacks