Walter said:
I am trying to update a seven year old computer. My 20GB hard drive should
probably be replaced. What is faster, a 9ms read IDE PATA drive connected to
the IDE on the motherboard, or a 9ms read SATA drive, connected to the
motherboard via a SATA controller? Any noticeable difference?
Thanks
The extra performance of the SATA interface, only helps for smaller data bursts.
Once you start transferring larger files, the head to platter interface becomes
the limiting factor.
For example, the second generation of SATA runs at 300MB/sec. The cache on the
disk might be 8MB in size. If you wanted to write some data, the data could be
stored in the cache memory chip on the disk. On some motherboards, the transfer
might be 220MB/sec or so, into the cache. That would seem fast, except the transfer
time is relatively short anyway, so you aren't doing a lot of waiting around.
If you have a 1GB file to transfer, the first 8MB might go into the cache chip.
But the cache is first in, first out, and so from now on, the cache can only go
as fast, as it is being drained. The head-to-platter interface is 70MB/sec, so
that is as fast as the write cache can be drained. After the first 8MB has
been transferred and the cache is full, now the disk transfer slows down.
And 70MB/sec is now slower than an IDE cable might be (100MB/sec or higher).
The IDE cable could easily handle that sustained rate.
The IDE cable would have a lower burst speed to cache, so the first 8MB might
only transfer at 133MB/sec or 100MB/sec etc (or less, if there are chipset
limitations, such as might exist on older chipsets). When you are transferring
the large file, the IDE drive now has the same 70MB/sec limit as the SATA drive
did.
So for burst write, SATA can be faster for small files. For sustained transfer
and equal platter technology, they are the same transfer rate.
In any event, if you go to the disk manufacturer web site, you can get information
on a few more parameters than might be listed on the sales web site. And make your
decision based on what you find.
The latest generation of disks, give a little more than the previous ones.
For example, I have a couple Seagate disks, and the new one sustains 72MB/sec
while the old one is about 60MB/sec or so. So there is room to shop around and
compare specs.
Paul
