Home Recording Computer Doom: IRQ Conflicts, ACPI, and Misc Disasters

Brandon Drury —  January 13, 2008

This has been one hellish week for good ol’ Brando. Shortly after one of my Delta 1010s died, my computer has decided to perform a mutiny against me. It’s okay, while my computer is faster at math, I’m way better at illogical thinking and that’s exactly what this problem encountered.

The Problem
On Monday I recorded a metal band. It was just one song recorded in robo speed in one evening. Everything went great. The next morning, I sat down to mix the sound. The sound was all garbled like the sound you hear in Cubase SX3 when you add a plugin while the song is playing. Then clicks and pops would immediately consume the sound. There was no way I could mix! So much for having that mix done last Tuesday. (It’s Sunday and I hope to get started today!)

I need to point out that this problem was using my remaining Delta 1010 audio interface which has been reliable for me since 2001.

The War
You heard me say “clicks and pops”. That immediately suggests issues with latency or CPU power. I wrote a big article on that here: Home Recording Computers: Clicks, Pops, and Latency.

However, the symptoms didn’t quite add up for this to be a super simple fix.

  • My recording computer is super clean. I have Windows XP SP2, Cubase SX3, CD Burning software, virtual synths, plugins and that is about it.
  • To my knowledge, nothing changed from Monday night when I recorded the metal band to Tuesday morning when the problems began. I did notice that when I attempted to back up the folder for that band onto my 3rd hard drive, the computer had locked up. This was VERY odd. On restart is when all the problems began.
  • When I experienced these dreadful audio problems, Cubase SX3 would have trouble playing just a single track, but it was clear that the noises, clicks, and pops increased as the track count increased.
  • There was no noticeable difference in the amount of noise, clicks, and pops when I slapped a few high CPU usage compressors on the 2bus.
  • Playing the same wave file in Cubase or Windows Media Player had drastically different results. Media Player had no problem playing back the file. Cubase did.
  • The CPU usage in Windows and in Cubase SX3 (F12 shortcut) never went over 50%. I wish I would have looked to see how much CPU usage Windows alone was using with no other programs running. This CPU usage issue is a big one. Usually when there are clicks and pops the CPU is being overloaded.
  • Changing the latency made absolutely no difference.
  • I thought that maybe this Delta 1010 was having big issues too. In came my new Presonus Firestudio. I heavily debated fixing the problem with the Delta 1010 or trying out the new Presonus Firestudio with the hope that the problems would be fixed. That caused it’s share of problems in regard to Presonus not exactly going out of their way to make their requirements known, but that’s another blog altogether. It turns out that the problems were exactly the same for both the Firestudio and the Delta 1010.
  • I had this exact same problem one month before. Simply formatting Windows fixed the problem. I had the feeling that there was a simple solution of changing a single setting or maybe overwriting a file, but it seemed faster to format than it did to look for that one file. This time around, the problem still existed even with a Windows format. This made me think the problem was hardware related.
  • I thought I had errors on my hard drives. I ran both Scandisk within Windows and chkdsk via command line. This did not solve the problem.
  • At this point, I was a bit frustrated. It didn’t appear to be a software issue in Windows and it didn’t appear to be a hard drive issue. In other words, my file system wasn’t the problem. This is where it gets scary. I had to go deeper than anyone EVER wants to go. I had to deal with IRQs.

IRQs – Interrupt Request Questions…no Quarters….no Quail.
Okay, as I hope heading illustrates I don’t know much about IRQs. I don’t pretend to. Anyone who enjoys IRQs enough to learn what they really do should consider getting out more. I’m the biggest hermit nerd I know of and want NOTHING to do with this IRQ business.

The way I see it, the IRQ is the little ports deep inside the skull that connect to the computers brain. If there is a bottleneck and too many merchant ships are trying to dock in one port, the goods don’t get moved in and out as fast in that particular port even though the overall brain isn’t really having problems. (Note: This is my current understanding. If someone really knows what they are talking about, please nicely correct me. This blog isn’t intended to be a 100% fact. It never is! Ha ha! It’s intended to be a journal of my experiences and thoughts that may help others solve their problems.) So, if you think you may be experiencing IRQ issues, heaven forbid, but a more nerdier dude than me! There are many tutorials that will bore your eyes right out of your sockets!

So, it was my guess that I was having an IRQ conflict. Too much data was moving in and out of IRQ X and that was causing a bottleneck. Of course, I have no idea how or why this would have changed over night. Something clearly did!

The way I understand it, the IRQs in XP are handled “virtually” and automatically. (This is called ACPI) In other words, Windows XP is pretty smart and can generally figure out the best place to put each device to make sure there are no bottlenecks. When I viewed my IRQ settings in Windows XP I did see that I had A BUNCH of components on IRQ 11. However, I hear that because Windows does all the IRQ handling via ACPI, these numbers really don’t mean a whole lot. GREAT!

The only way to change the settings in XP is to change from ACPI to “Standard PC” mode. This can cause major problems, but if you are dealing with IRQs you are probably already screwed anyway. It’s a gamble worth playing with. The idea is to switch “manual mode” using Standard PC so you can set the IRQs in your BIOS yourself. (In English, this means you send some of the cargo ships to San Diego, some of the ships to Los Angeles, and some of the ships to San Francisco instead of cramming them all into LA automatically using Windows). Switching to Standard PC can require a format. It can also require that you change yo ACPI settings in your BIOS. This is hardcore stuff. I’m not explaining it in great detail because I don’t feel like I’m qualified to. Again, see some robo-nerd website if you are considering suicide…I mean, switching from ACPI to Standard PC.

Back To The War
Now that we have poorly defined this IRQ conflict business, let’s get back to My Struggle. (Good book title for the average home recording guy! Too bad it’s already taken!) Anyway, so I start playing around with this Standard PC stuff. I try to manually set my IRQs in my BIOS. No matter what I did, I couldn’t seem to get the results I wanted. I must have missed a setting or something. I found that my BIOS didn’t react the way I had expected in regard to setting IRQs. (I had done this once before back in the day and that BIOS was much easier to use). I said “SCREW IT, F@%K, @#%^% 6^$#@#@$$” (imagine the dad from “A Christmas Story” or maybe Joe Pesci in “Casino” or any other movie.) I then went back to ACPI. Of course, this required a formatting because things go REALLY weird. (A “Standard PC” driver for my ATA controller decided it didn’t want to go away and therefore my 2 audio drives were not accessible). A formatting fixed all this junk.

After this junk, I re-installed Cubase SX3, the drivers for my new Presonus Firestudio, and fired up a mix. It had a little trouble playing, but we seemed to be 90% back in business. I hadn’t done a single Windows optimization because I figured I’d be formatting 17 more times that day. After doing the usual Windows XP optimizations, it appears that I’m 100% back in business. Frankly, I’ve been too scared to fully test!

This reminds of that part in Grumpier Old Men where Rocky’s trainer is 150 years old. He tells a story about how he is 200 years old and every morning he’d wake up and eat bacon and drink beer. For lunch, he’d eat bacon and drink beer. For supper he’d eat bacon and drink beer. The son says “What’s your point, dad?”. The Penguin from the original Batman series replies “POINT? There’s no point! I just like that story!”.

I didn’t learn a damn thing from this whole episode except that I need a way to backup / restore my rig fairly quickly in the future. (That’s a future blog). I have no clue how I fixed the problem. All I know is I wasted almost 4 days working on this damn problem and had to cancel 2 sessions.

Brandon Drury

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Brandon Drury quit counting at 1,200 recorded songs in his busy home recording studio. He is the creator of and is the author of the Killer Home Recording series.

3 responses to Home Recording Computer Doom: IRQ Conflicts, ACPI, and Misc Disasters

  1. I’m guessing this is what I have to go through if I don’t end up getting a new computer (PC > Mac). I put my pc together myself and having the same damn issues, but I was under the assumption it was the Firestudio (as others have had the same click/pop and now complete system crash problem using the Firestudio).

  2. Clicks and pops while recording are a symptom of some hardware conflict, probably an IRQ conflict like you said in your blog. One easy thing you can check ios to nmake sure your drive(s) are using DMA access. ACPI is the way to go, manually setting IRQs is not adviseable for 99.99999% of the problems you may encounter, that feature id a last resort for some old (like ISA) device that you have to manually set IRQ and I/O address with jumpers. has the definitive list of optimizations for recording music on Windows XP. THe key is to have a cutomized setup for recording that you do not use for anything else, especially email or browsing the internet. I have a dual boot setup on my laptop, it has two partitions both using Windows XP, one is optimized for recording adn has networking disabled. The other partition is a general use setup I can use to conect to the internet. Also one you have a good setup, immediately save an image of the hard drive to a backup device, such as an external USB drive. A good imaging program that I use is Acronis True Image, Symantec Ghost is also good.