David Tubbs wrote: > At 15:10 30/04/2007, you wrote: > > >>I must admit, I was assuming Sinclair had used 1024 byte blocks on his >>microdrives - I may need to be corrected on that. >> > > 512 byte seectors. > one map sector, one byte for each potential sector, I had a few mdvs > of 250 sectors.
didn't it have 1 word, 2 bytes per sector: the file number in one byte ($f8 = sector map, $fd = free, $ff = dead) plus the block number within the file in the othe byte? > > Note tpp, every file fragmented of necessity by the interleave factor > allowing the QL to digest the data from one sector before reading the > next, some 11 or 13 further on. If the file were contiguous it would > require a full revolution between sector reads. That begs the question of what one means by fragmented? If the sector allocation is such that some are deliberately skipped (interleave) then surely a fragmented file would be one that doesn't use the preferred sector(s), which for DOS users (with hard disks) would be the next contiguous sector (apparently). > I had some of the Psion package which were "Turbo Load", laid out for > optimum pickup speed, they had to be copied by special procedure > equivalent to a DOS DISCOPY. I never did that, but I had heard of it being done - the file laid out so that when the QL had digested the current sector, the next required one would be passing the read head...did it take into account "scatter"[1] loading? [1] As each sector has a file number and block number, it's position in the file is instantly recognised when read and if a later block happens past the read head before an earlier one, it is loaded first, into the correct memory. _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm
