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Re: Disk drive speeds

Big Bird wrote:

In article <lyNNd.2523$mG6.1575@newsread1.news.pas.earthlink.net>,
Rick Cortese  <ricortes@earthlink.net> wrote:
< < Ultimately you are talking about what a .1 MIP 6502<which is what < all the computers in question perform at> 
Are you talking standardized VAX-MIPS or native MIPS? IIRC, the
average number of cycles/instruction for the 6502 was a fair bit less
than 10.


Right.  I'd guess the average CPI is about 3 for the 6502 in most
situations.

And the issue is usually not what the theoretical maximum speed
of data transfer is, but what it is when doing ordinary disk
operations like program loads and saves, random file access, etc.

In these cases, the OS usually has a lot more to do with the realized
data transfer rate than the raw hardware!

I would agree with Andy that the Apple, using ProDOS, accesses 5.25"
floppy disks with an effective transfer rate in the 10-12KB/sec range
when doing typical operations on large files.

If loading a 10KB binary file, almost 3 seconds elapse before the
prompt returns, since the drive must be spun up, a directory lookup
done, a track/sector list read, and then the data read.

(I'm too used to a hard disk.  ;-)

-michael

New Applesoft BASIC interface for NadaNet networking!
Home page:  http://members.aol.com/MJMahon/