>I think the Windows NT kernel is a very underrated piece of technology - the reason it was unstable in the beginning is due to a corporate top-down decision: t

>I think the Windows NT kernel is a very underrated piece of technology - the reason it was unstable in the beginning is due to a corporate top-down decision: the hardware of the time was limited so they included GDI stuff in the kernel (crappy code not written by Cutler's team). Err, no. The reason it was unstable in the beginning were choices like having a "MUST SUCCEED" kernel memory pool which caused a bugcheck if the system could not allocate from that pool. Random kernel components allocated from this pool and if you opened too many handles (sockets for example), you'd get a bluescreen because an unrelated driver was trying to allocate memory for some other activity. There were probably other similar choices that I don't remember now. It has been 25+ years. And let's talk about the NT Driver I/O model. The most highly complex, over-designed POS I have ever seen. And this design was "polluted" for performance out of the gate (Fast I/O path, for example). It took Microsoft years to reliably and safely cancel pending I/O in the kernel. Remember the days when a random peripheral driver could hold on to an IRP and cause bluescreens all over the place because the process it was doing I/O for exited ? It was hard for internal Microsoft people to write good drivers, let alone OEMs in the wild with a fraction of the learning resources at their disposal. NT was based on the microkernels that were fashionable in those days (e.g, Mach from Rick Rashid et. al). As with most academic ideas, when microkernels met the real world they had to be adapted. Win32K came about because GDI performance in NT was crap. There were other things that were similarly pushed into the kernel already. I believe a classic microkernel would also have networking modules in user mode, for example. DirectX in the kernel (hated by the purists back in the day) is inarguably responsible for NT being able to supplant Win9x in the consumer PC market. The NT kernel evolved over the years to be something that actually met the needs of Microsoft's customers. I would argue that's the real achievement, and not all of that can be laid at the feet of "Cutler's team". I second the recommendation for "Show Stopper" :-)