I have not played with SDCC, but I have recently seen code compiled by SDCC running on a DS89C440; it worked fine, and that's about all I know about it. Keep in mind that the DS89C4x0 devices are fully 8051 code compatible, and these devices do not have any exotic features that strictly require low-level compiler support (i.e., larger than usual address spaces, etc.) to use. Numerous non-standard features provided by the DS89C4x0 such as page modes and stretch cycles are entirely instruction set-independent hardware notions; all that is required to leverage them is writing the proper values to the appropriate SFRs to configure these features. As others have pointed out in this thread and threads before it on similar topics, if you are lacking the required SFR definition headers, you can easily write your own.

Now, all of that said, some level of support from your tools can be helpful here, but is still by no means required, and has nothing to do with what compiler you are using; for example, standard library routines that leverage the device's dual data pointers can yield a performance increase. Still, this is by no means a necessity for functional correctness.

--Sasha Jevtic