MCGRATH@CSLI.STANFORD.EDU (James McGrath) (11/10/86)
The level of density considered "safe" or "proven" in the hard disk drive market is a hard question to give an unqualified answer to. First, remember that the 5 1/4" form factor is not usually a technology leader - most of the features you find there have already appeared in larger (diameter) disk drives. Second, sheer increases in areal density (fci (flux changes per inch) * tpi (tracks per inch)) is not the only way to get higher capacity. Although I have not back engineered Maxtor's 760 MB (actually 600 MB formatted), they probably got a fair amount of the density increase by just adding more platters, possibly increasing the recording radius from the standard 1" or so, maybe using other than a 2,7 RRL code, etc... In 5 1/4 " I have seen kfci in the low 20's and tpi in the 1800's (although not at the same time!), giving you something like 350 M fc/surface, or 500 M bits/surface, or 60 MB/ surface. So an 8 plater drive can give you a raw capacity of 960 MB (formatted capacity is considerably lower). For a user the real question is how much of this capacity can you get at a reasonable price. Maxtor is in the very high capacity, peformance, and price market. Companies such as Quantum and Micropolis do not push the boundaries as hard, but do turn out a less expensive product. Here we are currently shipping 160MB, low 20 ms average seek time drives. In the near future the 320MB products will begin shipping in quantity. Behind us are the Seagate's of the world, where 40 MB is the current standard and price means everything. Note that 40 MB was considered the boundary a few years ago. Thus all of the companies are in a continous migration to higher capacities. Expect more and more for less and less. Jim Note: I work for Quantum, but everything I do and say is in no way connected with my employment nor authorized by my employer. PS: given that the limits on system performance are usually associated with memory access, not raw CPU power, it is amazing that people don't spend much time talking more about memory, especially secondary storage.