KARATCHENTZEFF_Patrice/france_crolle_cr@gnx003 wrote:
> > Salut,
> > ne serais tu pas overclocke ? Les disques UDMA ne supportent pas
> > l'overclocking si tu ne descends pas a la main le PIO4 en PIO3.
>
> J'avais lu cela dans la doc linux. Il semblerait que les bus (PCI je
> suppose vu la fréquence...) ne doivent pas dépasser 33 MHz. Mais je ne
> vois pas bien le rapport avec le disque...
si tu overclockes le CPU, les bus suivent et donc disque dur, video et son
(uniquement l'interface, les codecs restent a 44100. Ainsi en passant de 66
a 75 tu gagnes sur tout les tableaux.
>
>
> Dans tous les cas, je n'overclocke jamais rien. C'est idiot, fait gagner
> des broutilles (et encore...) tout cela pour un risque sérieux
> d'endommager le matériel. Si je veux de la puissance, ce n'est pas vers
> Intel et consort que je me tournerai... DEC sait faire depuis des années
> des bons processeurs... et IBM n'est pas mal non plus. Mais c'est un
> autre débat ;-)
>
> Dans tous les cas, à moins d'une configuration par défaut délirante, ma
> configuration était normale.
>
> Au fait, qu'est-ce le PIO4 et 3 ?
Ci joint un extrait en anglais de la norme:
10.2. What are PIO modes?
The PIO mode determines how fast data is transferred to and from the
drive. In the slowest possible mode, PIO mode 0, the data cycle time
can not exceed 600 nanoseconds. In a single cycle, 16 bits are
transferred in or out of the drive. In a single sector, there are 256
words (16 bits = 1 word); 2048 sectors make up a megabyte. So,
mathematically,
1 cycle 1 sector 1 megabyte 2000
-------- --------- ------------ = ------ = 3.3MB/s
600ns 256 words 2048 sectors 600ns
So, the theoretical transfer rate of PIO Mode 0 (600ns cycle time) is
3.3 megabytes per second.
Here are the rest of the PIO modes, with their respective transfer
rates:
PIO mode Cycle time transfer rate
(ns) (MB/s)
0 600 3.3 ATA
1 383 5.2 ATA
2 240 8.3 ATA
3 180 11.1 ATA-2, IORDY required
4 120 16.6 ATA-2, IORDY required
5 90 22.2 vaporware
The first three, PIO modes 0 to 2, are old modes also present in the
old ATA standard. The others (PIO 3 and 4) are ATA-2 specific and use
IORDY hardware flow control. This means the drive can use the IORDY
line to slow down the interface when necessary. Interfaces without
proper IORDY support may cause data corruption in the fast PIO modes;
in that you're stuck with the slower modes, and typically half the
bandwidth.
When interrogated with an Identify Drive command, a harddisk returns,
among other things, information about the PIO and DMA modes it is
capable of using.
10.3. What are DMA modes?
DMA or Direct Memory Access means that the data is transferred
directly between drive and memory without using the CPU as an
intermediary, in contrast to PIO. In true multitasking operating
systems like OS/2 or Linux, DMA leaves the CPU free to do something
useful during disk transfers. In a DOS/Windows environment the CPU
will have to wait for the transfer to finish anyway, so in these cases
DMA isn't terribly useful.
There are two distinct types of direct memory access: third-party DMA
and first-party or busmastering DMA. Third-party DMA relies on the DMA
controller on the system's mainboard to perform the complex task of
arbitration, grabbing the system bus and transferring the data. In the
case of first-party DMA, all this is done by logic on the interface
card itself. Of course, this adds considerably to the complexity and
the price of a busmastering interface.
Unfortunately, the DMA controller on ISA systems is ancient and slow,
and out of the question for use with a modern harddisk. VLB cards
cannot be used as DMA targets at all and can only do busmastering DMA.
It is only on EISA- and PCI-based interfaces that non-busmastering DMA
is viable: EISA type 'B' DMA will transfer 4MB/s, PCI type 'F' DMA
between 6 and 8MB/s.
Today, all modern chipsets, including the ubiquitous Triton chipsets,
incorporate a busmastering DMA capable ATA interface. Efforts to
standardize the DMA hardware will ensure stable and reliable software
support.
Anyway, the DMA modes supported are:
DMA Mode Cycle time transfer rate
Single word (ns) (MB/s)
0 960 2.1 ATA
1 480 4.2 ATA
2 240 8.3 ATA
Multiword
0 480 4.2 ATA
1 150 13.3 ATA-2
2 120 16.6 ATA-2
! DMA/16 120 16.6 Ultra-ATA
! DMA/33 60 33.3 Ultra-ATA
The single word DMA modes are hardly useful and are obsoleted in
ATA-3. Note that some older interfaces are able to use these DMA
modes as a way to communicate with the drive, without actually doing
direct memory access at all. In these cases, the DMA modes are just
used as glorified PIO modes.
