Re: [TUHS] Fwd: Choice of Unix for 11/03 and 11/23+ Systems

I'm not sure I understand this ("worthwhile to implement RAW device"); let me explain what the removal of 'raw' I/O devices from MINI-UNIX really means, and then ask what it is that you are after. Early Unix (no idea about later ones) supports two classes of devices; 'block' devices, which can be used to hold file-systems, and 'character' devices, which cannot. (I seem to recall a paper, perhaps from the Unix BSTJ issue, which talks about them in some detail.) The former are those where the underlying physical device has restricted semantics; they are block-addressable mass storage devices. All access to them is via the system's block buffer pool, so reads/writes by the user of arbitrary size and location are possible. 'Character' devices are everything else. 'Raw' devices are an interface to the devices of 'block' devices which does not go through the system's buffer pool; I/O operations to them perform DMA directly to the user process' memory. They are 'character' devices, in the Unix device taxonomy. The only semantics available are those supported by the hardware - e.g. seeks only to block boundaries. So when I say that MINI-UNIX doesn't have 'raw' devices, it just means that e.g. the RK disk controller device _only_ talks to the Unix block buffer system; if a user program wants to look at the disk contents, it has to go via that system. So, with that in hand, what exactly is the need you forsee for raw devices in MINI-UNIX? Also, I've started to work on getting the V6 RL driver to work in MINI-UNIX; it should have been easy (just delete the charater device interface), but for some reason it didn't work when I tried it. I'll look at it in more detail 'soon'. Noel