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PIO vs. DMA revisited

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PIO vs. DMA revisited

Postby Pilgrim on Mon Mar 03, 2003 2:18 pm

Nearly everyone recommends that if you can, use DMA for all drive devices. I have read all the advantages of the increased "speed", etc. But I have a problem, hehe.

PC Specs: AMD Athlon XP 1800, WD 40 gig 7200, 512 DDR RAM, MSI K7T 266 Pro 2 MB, Lite-on 52246S Burner, LG CD ROM CRD 8522B. Iomega 250 atapi Zip. Win XP Home SP-1

Configuration: Primary - HD "0"; CD ROM "1" .. Secondary - Burner "0"; Zip Drive "1"

Here's the problem. If I enable DMA (Ultra DMA 2) for the Lite-on burner, seek and load times are slow. In fact, if I try to "Open" or "Explore" one of my CD-RW backup disks before the burner spins down, Windows Explorer freezes and generally the only way out is to hard reboot. The same thing happens if I let the disk data fully load but then try to delete/add/modify a file too quickly in sequence. However, if I switch to PIO mode, these same disks load MUCH quicker and I haven't had any freezing problems so far.

Question: If this is incorrect behaviour, what could be wrong and what is the fix.

Need further information? Just ask...... Image

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Postby cfitz on Mon Mar 03, 2003 2:31 pm

What you are seeing is believable. PIO mode is slower and consumes more system resources, but is generally more compatible. It used to be pretty standard advice: if you are having trouble with DMA, switch to PIO. Unfortunately, though, PIO has its own drawbacks as you are aware. And these days DMA can usually be made to work properly.

What drivers are you using for your IDE controller? On my W2K system, I found that the default drivers supplied by Microsoft work better than VIA's 4 in 1 drivers. Whichever you are using, you might want to switch and see if the other works better for you.

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Postby Pilgrim on Mon Mar 03, 2003 3:49 pm

cfitz,

I'm using the default Microsoft drivers: 5.1.2600.0

Yes, the consensus is that DMA is supposed to be faster, but not in my case. That's why I posted here. Using PIO is noticeably faster than the "Ultra DMA Mode 2" on my machine. And I don't get the freeze up problem either. Perhaps the advantages of DMA aren't cut and dry and that there are exceptions, of which I happen to be one? hehe But this is what I'm wanting to know; if my situation is unusual and there is something not right that is causing this to happen.

Thanks for trying to help out.

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Postby cfitz on Mon Mar 03, 2003 5:21 pm

The problems you are having with DMA are not normal, and something is not right. DMA, as a general technology, is unequivocally faster at transferring data than PIO. The fastest PIO transfer rate is 16 MB/s, while UDMA will currently go up to 133 MB/s (not that this really matters for a CD-RW drive like yours whose interface only supports up to 33 MB/s and doesn't even need that much bandwidth anyway). DMA is also dramatically more efficient than PIO, since PIO requires that the CPU transfer every byte of data that goes across the interface. In just about every aspect, DMA is clearly superior to PIO. The only exception is that PIO mode is, in some increasingly rare situations, more compatible. It is that cut and dry.

You are certainly welcome to use PIO if it is serving your needs, and if the troubles you are experiencing with DMA can't be cleared up then PIO is the way to go. But before you give up on DMA, I would suggest at least two things. First, make sure that you aren't being limited by PIO. Run transfer rate tests with CD Speed ( www.cdspeed2000.com ) for a good quality blank CD-R, a full recorded CD-R, and a full pressed CD. If you can't reach 48x-52x rates, then PIO is slowing down your system. Also check the CPU usage while these tests are running.

Second, try the VIA 4 in 1 drivers. They weren't as good as the Microsoft drivers in my case, but they might be better in your case.

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Postby Han on Mon Mar 03, 2003 6:06 pm

The main issue represents your ZIP drive, which doesn't support DMA and is hooked to the same cable as Lite-On is...
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Postby Pilgrim on Mon Mar 03, 2003 6:55 pm

Han wrote:The main issue represents your ZIP drive, which doesn't support DMA and is hooked to the same cable as Lite-On is...

Hmmmmm, now that doesn't appear to be true, Han. Looking at my Advanced Settings for the Secondary IDE Channel shows that the Zip Drive is using "Multi-Word DMA Mode 1".

cfitz,

I'll run the tests and see what results I get and report back. Image

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Postby cfitz on Mon Mar 03, 2003 7:40 pm

Pilgrim wrote:Hmmmmm, now that doesn't appear to be true, Han. Looking at my Advanced Settings for the Secondary IDE Channel shows that the Zip Drive is using "Multi-Word DMA Mode 1".

Things may have changed with the introduction of the 250 and 750 models. I don't know, since I've never owned a Zip drive. But that does bring up a good point. In the past Zip drives were sometimes known to cause trouble when sharing an IDE bus with a CD-RW drive. So you might also want to try the CD-RW in DMA mode with the Zip disconnected. And if that clears things up, you might want to swap the master-slave relationship between the Zip and the CD-RW, or try swapping the CD-RW and the CD-ROM (although I would prefer to have the CD-RW on a channel separate from the hard disc), or even dumping the Zip drive. :wink:

Since these sorts of changes are easier to undo, in my opinion, than driver changes, I would try them first if you read this in time. And since you are running XP, it would be wise to take advantage of the system snapshot feature and record your system state before changing any of the drivers.

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Postby jase on Mon Mar 03, 2003 7:44 pm

Trying to get UDMA working on the same cable as multi-word DMA (PIO) on a Via chipset is a nightmare in my experience. The Zip drive could be blocking comms and causing timeouts and all sorts of other horrible things.

My advice would be to remove the Zip drive temporarily and try again...
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Postby Pilgrim on Mon Mar 03, 2003 9:17 pm

cfitz,

All righty..... here are the results of my tests. I ran similar tests wtih both CD-R's and CD-RW's, using Nero CD Speedtest. Using the same disk, I ran each using DMA and then PIO.

Speedtest using CD-R disks

Speedtest using CD-RW disks

After you comment on the results of these tests. Then perhaps we can discuss the recommendation of switching the configuration of the drives. Image

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Postby cfitz on Mon Mar 03, 2003 9:34 pm

As expected, your throughput is being seriously degraded in PIO mode. This is easiest to see in the CD-R tests. Note that maximum transfer rates obtained in DMA mode approach 48x (and would be higher with fuller discs), but are capped at 19x~22x for PIO mode. Also note the much higher CPU usage in PIO mode reported by the tests - 43% versus 11%. All of these are the classic symptoms of inefficient PIO data transfer.

Your CD-RW tests aren't as dramatic because when writing, the transfer speed is limited by the CD-RW media itself at levels below that which both DMA and PIO can support. And when reading, the DMA advantage does show, but isn't as pronounced because, again, the media itself is limiting the read speed.

As for where to go from here, I would suggest following the steps I listed in my last post, beginning with a test of the system's stability with the CD-RW in DMA mode but the Zip drive disconnected, as suggested by Han, Jase and me.

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Postby KCK on Mon Mar 03, 2003 9:34 pm

Pilgrim:

Since you wrote about trying to delete/add/modify a file on a data disc, I wonder if you are using any packet writing software, such as DirectCD or InCD.
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Postby cfitz on Mon Mar 03, 2003 9:35 pm

KCK wrote:Pilgrim:

Since you wrote about trying to delete/add/modify a file on a data disc, I wonder if you are using any packet writing software, such as DirectCD or InCD.

This is another good point. I notice in one of your CD-RW test results that the medium could not be ejected - a possible symptom of packet writing software controlling the drive?? If you are having InCD problems, KCK is your man with the answers.

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Postby Pilgrim on Mon Mar 03, 2003 9:54 pm

KCK wrote:Pilgrim:

Since you wrote about trying to delete/add/modify a file on a data disc, I wonder if you are using any packet writing software, such as DirectCD or InCD.

KCK,

Yes, I am using the latest version of InCD, which is not enabled to run at startup. I start InCD manually whenever I need to format a CD-RW. Otherwise, it is not running at all.

All but the blank, CD-RW disk in the tests were formatted disks.

Okay... I'll open the case and disconnect the Zip Drive, enable DMA for the burner and then try playing with the files on my backup CD-RW disks as I normally do to see if the "freeze ups" occur. UNLESS you can suggest an easier way to disable the Zip Drive! Image

Let me say that I greatly appreciate the time taken to try and troubleshoot this problem of mine.

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Postby cfitz on Mon Mar 03, 2003 10:02 pm

Pilgrim wrote:Okay... I'll open the case and disconnect the Zip Drive, enable DMA for the burner and then try playing with the files on my backup CD-RW disks as I normally do to see if the "freeze ups" occur. UNLESS you can suggest an easier way to disable the Zip Drive!

That is the surest way. And maybe it is just my biases showing, but to me physically disconnecting the drive seems like the easiest way. :wink: And of course you don't have to remove the drive itself, or even both the power cable and the IDE ribbon cable. I'd prefer you to remove the ribbon cable if you remove only one, since that will remove any electrical load on the bus, but if that is truly a hassle, you could get away with just removing the power cable.

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Postby KCK on Mon Mar 03, 2003 10:19 pm

Pilgrim:

Apparently you have only removed InCD.exe from the Run entry in the registry. However, the InCD drivers bsstor.sys and bsudf.sys may still be loaded.

You should take a look at my InCD troubleshooting guide

http://www.cdrlabs.com/phpBB/viewtopic.php?t=9572

Note that the end of S11 there mentions possible conflicts with Iomega Zip drivers. Thus you may need to disconnect the Zip drive, and uninstall its drivers as well.
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Postby Pilgrim on Mon Mar 03, 2003 10:41 pm

KCK,

Thanks for the additional input! Yes indeed, I have previously read through your InCD tome, with much edification and appreciation. And since you seem to be the resident InCD Ph.D, might you tell me if there is really any harm in NOT having InCD running in the background (InCD icon displayed in the SystemTray)? I used to allow it to run permanently, but I was told it was unnecessary and it only used up memory, etc., and served no purpose unless you needed to format a disk?

Let me disconnect the Zip drive per cfitz's recommendation and see if that makes any difference. If not, then perhaps the next step would be to change the configuration back to the way it was originally before I upgraded to the Lite-on burner. The original configuration was HDD PM and Zip drive PS..... CD-RW SM and CD ROM SS. However, I was told by many that this is not the ideal setup and thus when I installed the new burner, I changed the configuration to what it is now.

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Postby cfitz on Mon Mar 03, 2003 11:52 pm

Pilgrim wrote:The original configuration was HDD PM and Zip drive PS..... CD-RW SM and CD ROM SS. However, I was told by many that this is not the ideal setup and thus when I installed the new burner, I changed the configuration to what it is now.

Ignoring the Zip drive, that is actually a perfectly acceptable configuration. With one hard drive and two optical drives, there are two general configurations to choose from, depending on how you intend to use the drives the most:

http://www.cdrlabs.com/phpBB/viewtopic. ... 5144#55144
(Ignore the bits about buying IDE cables - they were specific to the other person's questions)

However, tossing the Zip in the mix does change things a bit. I would agree that it is preferable to keep the Zip off the IDE channel that has the hard drive. And in general it is better to also have the CD-RW on a separate channel than the hard drive so that, while burning, reads from the hard disc don't interfere with writes to the CD-RW. But given the difficulties in mixing UDMA and Multi-word DMA/PIO on VIA chipsets that Jase mentioned, and the potential InCD-Zip problems KCK mentioned, the best compromise between speed and stability for your system might end up being:

PM = WD hard disc @ UDMA 4 or 5, whichever it supports
PS = LiteOn CD-RW @ UDMA 2
SM = LG CD-ROM @ Multiword DMA 2
SS = Zip 250 @ Multiword DMA 1

In this case we are violating the rule-of-thumb that advises separating the hard drive and the CD-RW drive in favor of the separating the Zip from the UDMA drives. This assumes that you rule out the LiteOn as the source of the instability with the Zip-less tests you are running right now, and also assumes that you want to keep the Zip drive. But, I'm getting ahead of things here. Let's hear how your stability tests worked out with the Zip removed from the system.

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Postby KCK on Tue Mar 04, 2003 12:04 am

Pilgrim:

Since I have never made any extensive tests with InCD.exe prevented from running, I can't answer your question. When loaded, InCD.exe takes up about 3.5MB of memory, which shouldn't hurt on your 512MB box. Further, I have never experienced any slowdowns with InCD.exe running on my XP P-4M 2GHz 768MB box, or my 98SE PII 400MHz 256MB box. Thus apparently you won't gain much by preventing InCD.exe from running.

One thing you will loose is the InCD mounted message, which confirms that a disc is recognized properly. So a plausible explanation for your freezes is that you are calling up Explorer to access an InCD disc before this disc is recognized by the InCD drivers!

Thus, for now, please allow InCD to operate in its normal mode, and check if you still have freezes when accessing a disc after the InCD mounted message.

Re-iterating from my previous message, for testing purposes you may need to disconnect the Zip drive, and uninstall its drivers as well, since even with the Zip drive disconnected, Windows will probably load its drivers, and these drivers may be conflicting with the InCD drivers. Once everything works OK, you may try to reconnect the Zip drive and reinstall its drivers.
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Postby dodecahedron on Tue Mar 04, 2003 11:44 pm

Pilgrim wrote:...since you seem to be the resident InCD Ph.D ...

yes, i like that!!! :P
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RE: Tests w/Zip drive removed

Postby Pilgrim on Wed Mar 05, 2003 1:31 pm

cfitz & co.,

No noticeable changes were observed after removing the Zip drive & drivers. In fact, both before and after the removal of the Zip drive, things seemed to have gotten better?? Go figure! Image

And, with the burner now operating with DMA enabled, it is definitely faster than with PIO, which again is mysterious because the opposite was true since the burner was installed. Image

All seems rather bizarre to me! Image

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Postby KCK on Wed Mar 05, 2003 6:27 pm

Pilgrim:

Well, you seem to be glad with your current configuration. However, to help other users, could you try to make things less bizarre by providing more information?

Could you clarify the meaning of "things seemed to have gotten better"? Did you allow InCD.exe to run for your latest experiments?

In view of your initial problems, let's define "mount time" as the time elapsed between pressing a burner's button to load an InCD formatted disc and seeing the InCD mounted message (in other words, how long you must wait before accessing an inserted InCD disc).

I get average mount times of about 20 seconds (more exactly between 16 and 23 seconds) on a variety of 10x and 12x discs, formatted to UDF 1.50 or CD-MRW (no significant correlations here). These timings were obtained on my XP Pro box (P4-M 2GHz), InCD 3.52.00b, with Lite-On LTR48125W VS08 sitting in an external FireWire enclosure (hence no DMA setting). Since I have Autorun on for my burner, I kept the Shift key pressed while mounting discs to prevent Explorer from kicking in.

So could you report your mount times with DMA enabled and InCD.exe running? Are they significantly longer than with PIO?

You could also measure mount times when InCD.exe is not running; of course, instead of the InCD mounted message, you should wait for the Autoplay message from Explorer (this needs Autorun on). Well, I would keep InCD.exe running in normal operation, so this aspect is just a curiosity for me, but if don't want to run InCD.exe all the time, you should know how long to wait to avoid Explorer freezes.
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Postby Pilgrim on Wed Mar 05, 2003 8:30 pm

KCK,
Could you clarify the meaning of "things seemed to have gotten better"? Did you allow InCD.exe to run for your latest experiments?
Sorry for not including more detail! Image My burner now has DMA enabled. The Zip Drive is connected and configured as the slave to the burner on the Secondary IDE channel. InCD is running and enabled to run at Startup. "NeroCheck" in the Startup group has been disabled.

Transferring files from the HD to the burner to my favorite formatted CD-RW disk is now much faster than when it was using PIO, which we would expect. But there is no longer the "lag" when working with the files on the disk as there was before. Previously, if I had the "explore" view displayed in Windows Explorer and clicked on a folder in the tree on the left, the burner would begin to spin up and take some time before the files would show up on the right of the Explorer window with each files respective icon displayed.

In fact, I really pushed things to the limit by copying over large sections of a previous CD-RW to a new one, which before would cause the freeze. I even tried copying another group of files to the disk before the burner spinned down and was still writing (red light was on). There was a short delay, and then Explorer displayed the copy dialog and things continued as one would expect them to.

Mount Times: I clocked the time at 20 seconds using a formatted CD-RW that was full of written data and auto-run enabled, between the time I pushed the button on the burner to open the tray to when the InCD mounted message appeared. The disk itself is a "Plasmon" 4x CD-RW 74 min. I ran several of these tests with different media and the times were all about the same; i.e., 19-20 seconds.

Times without InCD running were nearly identical.

If there is any other information and/or tests you would like me to run.... just ask! More than glad to help; it would only be right, eh? Image

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Postby KCK on Wed Mar 05, 2003 10:33 pm

Pilgrim:

Thanks for the feedback.

Your IDE configuration looks reasonable to me, but cfitz should have the final word!

BTW, this is your initial IDE configuration, and the subsequent software changes amounted to reinstalling the Zip drivers, allowing InCD.exe to run, and enabling DMA for your burner.

Apparently your "Startup group" refers to the registry key

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

Why have you disabled NeroCheck? Since there is so much conflicting information about NeroCheck on the web, and Ahead still installs it with Nero, I think it is better to leave it running.

It is good to hear that your burner functions nicely with the Iomega 250 Zip drive. My reservations about InCD and Zip drives stemmed from users who apparently had earlier models.

Does "copying over large sections of a previous CD-RW to a new one" mean copying from the CD-ROM drive to your burner?

Since your timings agree with mine, we may conclude that mount times of about 20 seconds are typical for current versions of InCD and Lite-On burners. (Of course, I presume you meant "close the tray" instead of "open the tray".) :D
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Postby Pilgrim on Wed Mar 05, 2003 11:23 pm

KCK,

Let me say first, that I am pleasantly impressed with the amiable and patient responses I have received from you and others. Thanks!
Does "copying over large sections of a previous CD-RW to a new one" mean copying from the CD-ROM drive to your burner?
Yes, exactly. I must admit that the copy process was "disjuncted"; i.e., that it occurred in sections rather than a nice even flow from the CD ROM to the burner. I suspect this is because my CD ROM is using PIO (LG 8522B)? But copying similar data from the HD to the burner moves quickly and evenly.
Why have you disabled NeroCheck?
Only because of what I read what I read in the list here: http://www.pacs-portal.co.uk/startup_pa ... full.htm#N. In short, the recommendation said it was unnecessary unless you were trying to access Nero without Administrative rights. Do you know something more that would indicate that "Nero Check" should be allowed to run at Startup?
Of course, I presume you meant "close the tray" instead of "open the tray".
No, actually I meant, although perhaps I shouldn't have, "open tray". Image My timing began from the moment I pressed the button to open the burner tray until either the InCD splash screen or the autorun dialog appeared.
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Postby cfitz on Thu Mar 06, 2003 12:30 am

Hi Pilgrim,

Sorry about the delay. I've been busy with school and work. But it looks like you have been in good hands with KCK, as expected. :)

As I understand it, your current configuration is:

PM = WD hard disc @ UDMA 4 or 5, whichever it supports
PS = LG CD-ROM @ PIO 4
SM = LiteOn CD-RW @ UDMA 2
SS = Zip 250 @ Multiword DMA 1

I kind of hate not knowing what changed to make things start working well even with the Zip drive installed. But, as they say, the proof is in the pudding. So if things are working well for you now, that's what really counts.

Your configuration is, in general, a good configuation. It is optimized, with one exception, for on-the-fly burns and hard disc to CD-RW burns. The one exception is the PIO mode for the LG CD-ROM. I don't like to see that, particularly on the same channel as the hard drive. I believe that the LG will support Multiword DMA 2:

http://www.lgeus.com/Product/CD/crd_8521b.asp

Why don't you give it a try in DMA mode? If it gives you any problems, then we can think about changing to the configuration I suggested here:

http://www.cdrlabs.com/phpBB/viewtopic. ... 5901#55901

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