Re: [TUHS] System III - TCP/IP

Although the Z8000 has segments, they will require special code to access, and so you will have to regard it as a 16 bit CPU from the viewpoint of running ordinary unix kernel/applications. You can most likely implement a split I/D architecture by having code execute out of a different segment than data, although I haven't checked the datasheet so I don't know for sure if this is possible. You can also do a few other things -- you could for example make mbufs and bufs reside in different segments and wrap all kernel accesses to them in macros, which would free up significant space in the main kernel data segment. Or you could do what I did for the Z180 implementation, (the first try -- UZI / NOS derivative, not the proposed 2.11BSD port), which I somewhat borrowed from the IAR's Z180 C compiler -- the calling convention allows for a segment switch on function call and return, so you can have large multi-segment executables. In my implementation I had a 768 kbyte RAM disk which was formatted unix style (not BSD style unfortunately), but I had an alignment routine which put executable files into contiguous blocks on 4kbyte boundaries (normally the filesystem had 1kbyte blocks), and I created a mapping table, and I revised the IAR compiler's calling stubs to allow executing multi segment executables direct from RAM disk. This would work in your system with minor porting, but unfortunately it's not implemented in 2.11BSD, it's in my earlier code. You're welcome to it, though. The kernel and some of the utilities in 2.11BSD are large enough to require split I/D, I didn't have that, but proposed to get around it by using multi-segmented executables (my memory map allowed for 4 kbytes of stubs and utility code/data, 56 kbytes of data and 4 kbytes of the currently visible code segment). So you will have to either implement split I/D or multi-segmented executables, it doesn't matter which. Check how your sys3 system handles this, because you will probably want to take as much of the assembly code from the sys3 system as possible. So given you're implementing a 16 bit system, you should definitely go for 2.11BSD, it's simply the most advanced and the only reasonable unix system out there that executes in 64 kbytes. You can look at 4.3BSD, personally I looked at a later BSD and I discovered that the network stack is significantly cut down in 2.11BSD, and for good reasons. For example it does not implement syn cookies (protection against TCP SYN DOS attacks), presumably because this required some largeish kernel tables. You don't need the complexity, you want 2.11BSD I think. Nick On Mon, Nov 9, 2015 at 12:38 AM, Oliver Lehmann <lehmann(a)ans-netz.de> wrote: