Re: no merit from using DMA-66?

[Vachirasuk <vachi@pop07.odn.ne.jp>]

Hi,

I think I am trying to measure data transfer rate from harddisk. I
have read UDMA-mini-HOWTO on LDP site and it also said "UDMA drives
will give you between 10 and 15 MB/s using UDMA mode 2 (33 MB/s) or 4
(66 MB/s) enabled". If the DTR never gets higher than 33MB/sec then
why use DMA-66, since there is no performance improvement? How come
benchmark under Win98 gave me DTR of DMA-66 drive 2 times of normal
DMA-33 drive? Am I misunderstanding something here?

Confused

Vachi

-----
Vachirasuk Setalaphruk
ISE, Osaka University

From: "Stephan Hachinger" <Stephan.Hachinger@gmx.de>
Subject: Re: no merit from using DMA-66?
Date: Sat, 18 Mar 2000 21:35:53 +0100

> Hello!
> 
> Are you really sure you're measuring the maximal bus speed?
> 
> Because the bus speed (UDMA33=33MB/sec; UDMA66=66MB/sec) is only the maximum
> data rate which can be transferred. However, the magnetic disk can never be
> that fast, so that data rates of 16MB/sec are quite normal and not bad.
> 25MB/sec must be a very good hard disk. So, just don't worry, this high data
> rates can only be reached if the data comes from the HDD cache over the bus.
> 
> Kind Regards,
> 
> Stephan Hachinger
>