On 08/07/05 at 11:23 P Witte wrote: >> John Gilpin writes: >> 4Gb per QXL.win file...
>I only get 2GB with QPC2: FORMAT win8_4000 fails while win8_2000 doesnt. >Even then the file allocation block is a massive 32k. It seems to me that >4GB must be the theoretical limit for the current mapping scheme. The >minimum space taken by a file on disk would then be a whopping 64k > >Per Per is right, IIRC QLWA may have a 2G limit, even though 4G would be the theoretical maximum. There are two possible reasons for it: 1) Maximum number of allocation blocks (think of them as a sort of super-sector) is a 16 bit word, unfortunately, some implementations and versions took it a s a signed integer instead of unsigned. 2) Maximum size of one allocation block is a 16 bit word, again some implementations and versions used signed arithmetic to point to a byte within the block, which reduces it's maximum size to 32k. IIRC the first error is the more likely to crop up. When QUBIDE was being maintained, these cropped up, but I do not remember the speciffics any more. 4G is a sort of double limit as the system implies that the whole QLWA partition can be used up by a single file. Since the file pointer is a 32 bit unsigned (hopefully!) integer, the maximum size of a file is 4G, and so is the size of the partition (64k blocks each 64k in size = 4G). The serious limitiation here is that one file always takes up at least 1 allocation block (even if the file is empty!) and the less serious one is that there can be max 64k files. The first is quite restrictive in QL terms as files are, in general, much shorter than 64k. This produces a lot of wasted space. If you want to be absolutely sure, 1G QXL.WIN, with 32k allocation block size is the way to go, it avoids all the possible pitfalls... Nasta _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm
