On <03 Nov 94 13:11> [EMAIL PROTECTED] wrote: >> > I thought ProDos wrote CP/M format >> > disks, so why does it need to cache >> > anything?
Ia> Let me clarify that question. Why Ia> would calculating a random access on Ia> this system depend on caching, apart Ia> from storing the 32-byte directory Ia> entry(ies)? ... Oh never mind, I Ia> probably misunderstood the remark. Well when the cache contains the entire directory in which each extent contains its own allocation data one can calculate from the random record position to which physical extent to open and to find that extents allocation data one needs to pysically See the block allocation data and if its all in the cache then the only floppy access will be to seek the actual data on the disc, assuming it's not still in the cache from a prior read, in which case NO drive access at all would be required and hence very fast seeks are possible. If the cache only contains one or two directory sectors and they happen to be the ones we're after then fine as well! Does that explain it? If not don't worry, it works that's all that's important:-) Johnathan. ___ Olms 1.60 [Evaluation] +-------------------------------------------------------------------+ | Standard disclaimer: The views of this user are strictly his own | | ===> Gated @ Centronics BBS [centron.com] +44-1473-273246] <=== | +-------------------------------------------------------------------+
