A few quick and dirty calculations show that assuming that the PS3 has 256MBs of main RAM (who knows, it may have more), filling three quarters of it at 4xBR would take [EDIT] 10.667[/EDIT] seconds, assuming everything was ordered so as to make seek time insignificant.
This is about twice as long as filling a similar proportion of the PS2's memory would take.
I don't know what the roadmap for BR development shows (anyone?) but what kinds of speeds are we talking about by the end of 2005? I know comparisons to CD and DVD drives are unpopular, but the CD and DVD drives seen in consoles have always been a fair bit slower than high or top end PC parts, even on the consoles launch day.
The thing I'm thinking about is - yes - cost.
pcostabel said:
Wether or not BR will be rewritable in PS3 remains to be seen, but considering that a rewritable BR means no need for an HD, it might actually bring down the cost.
In terms of functionality, I don't think a BR device can [totally] replace a HDD. If Sony want the PS3 to become the home media hub, it needs to have software on the machine (in a similar fashion to the Xbox). What's more, it needs to be able to store a fair amount of this software, and it needs to be upgradeable and patchable.
After playing a game you don't want to have to put in a disk to load up the web browser (isn't Sony friends with AOL?), or DVD player, or TV recording software, or latest version of Playstation Live! etc. Xbox Live is a good example (hopefully) - the software has already been updated for it, but this process is supposedly mostly transparent to the user (not used Xbox Live myself), and features like messaging and chat can be updated centrally without worring quite as much about versions on older games.
For features associated with the machine, rather than with a particular game, a HDD makes sense. You could use internal flash ROM or some other solid state rewriteable media, but once the amount of software you want to run on your home broadband box starts increasing this becomes more and more expensive.
Plus, one of the most annoying things about a VCR is scrambling for a tape at the last minute. If I've got a state of the art Tivo style device, I expect to be able to press a button and have it record until I can find a disk to put something on.
Plus, if you've got a 4X BR device to load from it might be a good idea to have a HDD to cache data to.
Edited, because o' sloppy maths.