der Mouse wrote:
The 6-byte limitation of old VAXstations is not a limitation of the controller, but of the firmware in the boot monitor. [...] Once the OS driver takes over, it can use 8-byte disk block numbers.Well, it can try. Depending on how recent the disk is, it may not recognize 16-byte read and write CDBs (which are the ones with 8 bytes of block number).
Well, the point was that once the OS takes over, you are free to use whatever sizes you want. The limitation is not in the hardware (well, unless you count the disk, which obviously also have to understand what you are saying :-) ).
You're probably going to be better off with the 10-byte versions, which
have only 4 bytes of block number ("only" - 32 bits of block number can
address two terabytes of disk).
Right. And actually, I was confusing the size of the request with the size of the disk block address (which you probably suspected).
And, fyi: If you can make sure that the boot monitor will only access data in the first 1G of a disk, you can actually have a disk of any size also as the boot disk. And since Unix partitions the disk, all you need to do is make sure that the root partition (partition a) is less than 1G, and you are home free.The boot partition, actually, not necessarily the root partition. I have some Suns with the same problem (ROM code restricted to 6-byte CDBs) on which I have a tiny boot partition (a few tens of megs at most) and use kernels configured with root specifically put somewhere else. (I generally mount the boot partition as /kernels and symlink /netbsd -> kernels/netbsd.)
That is also a trick. Never thought of doing that. But then again, I have never felt the need for my root partition to be more than 1G anyway.
Johnny
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