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SubjectRe: PIO disk writes using 100% system time and performing poorly with VIA vt82c686b on kernels 2.2 & 2.4
Ignacio Monge wrote:
> Hi.
> I have VIA686a too and a UDMA100 hard disk.

So do I.

> This is my cat /proc/ide/via:
> ----------VIA BusMastering IDE Configuration----------------
> Driver Version: 3.23
> South Bridge: VIA vt82c686a
> Revision: ISA 0x22 IDE 0x10
> Highest DMA rate: UDMA66

> -------------------drive0----drive1----drive2----drive3-----
> Transfer Mode: DMA UDMA PIO PIO
> Address Setup: 30ns 30ns 120ns 120ns
> Cmd Active: 90ns 90ns 480ns 480ns
> Cmd Recovery: 30ns 30ns 480ns 480ns
> Data Active: 90ns 90ns 330ns 330ns
> Data Recovery: 30ns 30ns 270ns 270ns
> Cycle Time: 120ns 60ns 600ns 600ns
> Transfer Rate: 16.5MB/s 33.0MB/s 3.3MB/s 3.3MB/s

What is odd here is the 33MB/s on drive 1. If it was operating
at UDMA66, that would be more like 66MB/s (see my own /proc/ide/via).
I guess you should try putting a drive on IDEO as master and the
second on IDE1 (which seems empty) as master too.

> As you can see, l use UDMA66 instead UDMA100. I don't know why. Maybe VIA
> vt82c686a doesn't support it? I have answering in this list a days ago about this
> problem. but none seems to have a question.

686a maxes out at UDMA66. 686b does UDMA100.

> Like you, my system goes down when I try to compile so
> mething (I have a 394 Mb of RAM and a 1 Ghz processor).

I'm clueless, my 686a with IBM DTLA works fine (board is
ASUS A7V, kernel 2.4.3, Duron700, 256MB PC133). The new VIA
IDE fixes in the kernel _might_ be the cause, but I'm not sure.

> Although, my hdparm output is this:
> /dev/hde2:
> Timing buffer-cache reads: 128 MB in 0.79 seconds =162.03 MB/sec
> Timing buffered disk reads: 64 MB in 2.44 seconds = 26.23 MB/sec
> and sometime looks better.
> I don't know is this is a problem with the VIA kernel driver or not. But the
> system doesn't seem to work fine since 2.4.2 or 2.4.1 kernel. I hope (plz!) this
> problem will be fixed in future.
> Luck.
> PS: in cat /proc/ide/via I see "Cable Type: 40w > 40w"... Is it right? I have a 80w cable, not 40.

I see 80w in mine, maybe your cable is broken... Did you put the blue
of the cable on the motherboard ? Also detecting a 40w cable disables
UDMA66 I guess.

Here's my /proc/ide/via :

----------VIA BusMastering IDE Configuration----------------
Driver Version: 3.20
South Bridge: VIA vt82c686a
Revision: ISA 0x22 IDE 0x10
BM-DMA base: 0xd800
PCI clock: 33MHz
Master Read Cycle IRDY: 0ws
Master Write Cycle IRDY: 0ws
BM IDE Status Register Read Retry: yes
Max DRDY Pulse Width: No limit
-----------------------Primary IDE-------Secondary IDE------
Read DMA FIFO flush: yes yes
End Sector FIFO flush: no no
Prefetch Buffer: yes no
Post Write Buffer: yes no
Enabled: yes yes
Simplex only: no no
Cable Type: 80w 40w
Transfer Mode: UDMA PIO DMA PIO
Address Setup: 30ns 120ns 60ns 120ns
Cmd Active: 90ns 90ns 90ns 90ns
Cmd Recovery: 30ns 30ns 90ns 90ns
Data Active: 90ns 330ns 90ns 330ns
Data Recovery: 30ns 270ns 90ns 270ns
Cycle Time: 30ns 600ns 180ns 600ns
Transfer Rate: 66.0MB/s 3.3MB/s 11.0MB/s 3.3MB/s

François Cami


All that is gold does not glitter,
Not all those who wander are lost,
The old that is strong does not wither,
Deep roots are not touched by the frost.
From the ashes a fire shall be woken,
A light from the shadows shall spring,
Renewed shall the blade that was broken,
The crownless again shall be king.

The Riddle of Strider
JRR Tolkien
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