Re: [PARPORT] Speed of ppa 1.40 driver

Riley Williams (
Thu, 5 Feb 1998 11:10:01 +0000 (GMT)

Hi David.

>> I use the ppa 1.40 driver with kernel 2.0.33 on a >> I use the ppa 1.40 driver with kernel 2.0.33 on a 486@133MHz.
>> I used to get around 16-20 Mb/min with my ZIP drive (R/W).
>> This sank a bit to approx 11 Mb/min and in daily use the
>> performance got even more worse.

> There is a known "feature" (problem) with VFAT/UMSDOS/MSDOS
> partitions on ZIP disks. It has to do with MSDOS <=> UNIX text
> file translation.

I'd like to know more details about that, as I use VFAT on most of
my ZipDisks, and have yet to notice any speed degradation. Also,
since I have text file translation turned off, I find it very
difficult to accept that explanation.

There are two explanations I could understand relating to any
speed degradation, which are as follows:

 1. Filename translation: All three of those formats generate an
    8.3 format filename from the UNIX filename and naturally, that
    takes time. However, it's only done when the file is first
    opened, not every time the file is accessed, so the time taken
    to do so should be neglible compared to the time taken whilst
    processing the file.

 2. Disk fragmentation: All three of those formats can result in
    files being stored all over the disk, with a bit here, another
    bit there, etc. This will result in a slowing down when using
    the file in question, simply because of the time needed to
    move from one fragment to another.

Of the two, I'd tend to suspect the latter as being the cause of
the problem stated, since the complaint implies that largish files
are being referred to...

> Could you perform a test using:

> "time dd if=/dev/sda of=/dev/null count=20480"

> The above command should copy 10Mb from the ZIP drive and
> return the time taken.

I've regularly used the following command to check drive access
speed, slightly different from the above:

Q> time dd if=/dev/sda of=/dev/null bs=1024 count=40960

That copies 40M from the drive and, using that, I have measured
transfer speeds around 240k/sec on an EPP port and around 130k/sec
on an ECP port, which translate into 14.4M/min and 7.8M/min
respectively...and, on a system running SPP mode only, I have never
achieved better than 25k/sec (1.5M/min)...

Before you ask, on my computer, the EPP mode produces corrupted
ZipDisks but the ECP mode works fine. On a friend's computer, EPP
mode works fine. Both machines are P166's.

> If this is less than 20Mb then I am worried...

Presuming you mean 20M/Min, it sounds like you're quite worried...

Best wishes from Riley.

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This archive was generated by hypermail 2.0b3 on Wed 30 Dec 1998 - 10:17:24 EST