PIO mode

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Does the hardware involved check for errors during data transfer?

--
.~. Might, Courage, Vision. In Linux We Trust.
/ v \ http://www.linux-sxs.org
/( _ )\ Linux 2.4.26
^ ^ 1:36pm up 5:14 1 user 1.15 1.14

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

In article <slrncehq7i.6j5.toylet@server.donkeyware.org>,
toylet@hotpop.com says...
> Does the hardware involved check for errors during data transfer?

A CRC is computed for each packet of data. If it doesn't match, an error
is flagged and passed to the software. I believe it's up to the
software/drive firmware to figure out what to do next (usually retry a few
times.) I believe UDMA33 and higher have more aggressive error correction
and retries.

--
If there is a no_junk in my address, please REMOVE it before replying!
All junk mail senders will be prosecuted to the fullest extent of the
law!!
http://home.att.net/~andyross

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

"Andrew Rossmann" <andysnewsreply@no_junk.comcast.net> wrote in message
news:MPG.1b5322ffa94ac1c989a10@news.comcast.giganews.com...
>
> A CRC is computed for each packet of data. If it doesn't match, an error
> is flagged and passed to the software. I believe it's up to the
> software/drive firmware to figure out what to do next (usually retry a few
> times.) I believe UDMA33 and higher have more aggressive error correction
> and retries.
>
All UDMA modes have CRC, and PIO/DMA have none.

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

In article <ccbqp1016cs@enews1.newsguy.com>, ericgisin@graffiti.net
says...
> "Andrew Rossmann" <andysnewsreply@no_junk.comcast.net> wrote in message
> news:MPG.1b5322ffa94ac1c989a10@news.comcast.giganews.com...
> >
> > A CRC is computed for each packet of data. If it doesn't match, an error
> > is flagged and passed to the software. I believe it's up to the
> > software/drive firmware to figure out what to do next (usually retry a few
> > times.) I believe UDMA33 and higher have more aggressive error correction
> > and retries.
> >
> All UDMA modes have CRC, and PIO/DMA have none.

I guess it depends on what level everyone is talking about. There has
always been a CRC stored on the drive and it's checked when it reads the
data. If there are too many retry failures, it passes a failure code to
the controller. Back in the MFM/RLL/ESDI days, that was done on a card
separate from the drive, so you did sort-of check the integrity of the
signal in the cabling. With IDE, it's all built-into the drive, so before
UDMA33, it was assumed the data traveling on the cable always made it
through with no error. It's also why the 80-wire cable was required for
UDMA66 to give better shielding.

--
If there is a no_junk in my address, please REMOVE it before replying!
All junk mail senders will be prosecuted to the fullest extent of the
law!!
http://home.att.net/~andyross

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Previously toylet <toylet@hotpop.com> wrote:
> Does the hardware involved check for errors during data transfer?

Neither for transfer nor for commands. PIO is completely unprotected
on the bus.

Arno
--
For email address: lastname AT tik DOT ee DOT ethz DOT ch
GnuPG: ID:1E25338F FP:0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
"The more corrupt the state, the more numerous the laws" - Tacitus

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

"Andrew Rossmann" <andysnewsreply@no_junk.comcast.net> wrote in message news:MPG.1b5399a9652114b2989a12@news.comcast.giganews.com
> In article <ccbqp1016cs@enews1.newsguy.com>, ericgisin@graffiti.net
> says...
> > "Andrew Rossmann" <andysnewsreply@no_junk.comcast.net> wrote in message
> > news:MPG.1b5322ffa94ac1c989a10@news.comcast.giganews.com...
> > >
> > > A CRC is computed for each packet of data. If it doesn't match, an error
> > > is flagged and passed to the software. I believe it's up to the
> > > software/drive firmware to figure out what to do next (usually retry a few
> > > times.) I believe UDMA33 and higher have more aggressive error correction
> > > and retries.
> > >
> > All UDMA modes have CRC, and PIO/DMA have none.
>
> I guess it depends on what level everyone is talking about.

Simple: "Does the hardware involved check for errors during *data transfer*?"

> There has always been a CRC stored on the drive

Nope.

> and it's checked when it reads the data.

That's an ECC.

> If there are too many retry failures, it passes a failure code to
> the controller. Back in the MFM/RLL/ESDI days, that was done on a card
> separate from the drive, so you did sort-of check the integrity of the
> signal in the cabling. With IDE, it's all built-into the drive, so before
> UDMA33, it was assumed the data traveling on the cable always made it
> through with no error. It's also why the 80-wire cable was required for
> UDMA66 to give better shielding.