devices per IDE channel

chucksterchuckster Junior MemberMember Posts: 20 ■□□□□□□□□□
I was taking yuor a+ test last night and one of the questions was how many devices can be on a ide bus which I thought was 1 for the old ide standard and two if on the newer eide bus is this correct? Are am I mistaken. icon_confused.gif:

somewhat confussed


  • SartanSartan Senior Member Inactive Imported Users Posts: 152
    When IDE was first released along with the old IBM clones and the XT computers, 8-bit IDE was developed. IBM then later developed the 16-bit MCA standard, (hence being proprietary) and everyone whined about it and IDE was developed.
    IDE intitially supported a 16 bit address bus, with 2 bytes of transfer.
    -Two devices per channel, 2 bus's = 4 devices.

    EIDE was created primarily to escape the 504 mb hard disk limit. The "enhanced" bios was created, hence the 'e' in 'eide'. It was also developed to get faster, because something with the 386 chip (not the 386 enhanced) prevented speeds from reaching the limits of the physical drives. ~ PIO modes. All of this was in the bios, however the drives themselves still claimed EIDE.

    Western digital first claimed the standard and introduced a bunch of fancy things, including ultra DMA.

    Because western digital decided to claim "EIDE" or "EIDE Compatible" IDE cards to support the drives, they've become associated with the term.

    This double standard has led to the uselessness of the word, and all drives are now tagged EIDE. But none of this whooha gave it more channels.
    Network Tech student, actively learning Windows 2000, Linux, Cisco, Cabling & Internet Security.
  • WebmasterWebmaster Johan Hiemstra Admin Posts: 10,292 Admin
    Another great explanation Sartan icon_thumright.gif, although not entirely accurate

    chuckster, I'm sure the above explanation un-confused you, but I'm half way finished with the IDE TechNotesfor the A+ core exam and should be up within a couple of weeks. I hope it will explain things as it seems there is a lot of confusion about this topic. I noticed docs that claim EIDE to increase the amount of drives from 1 to 2, others claim that EIDE supports two busses instead of one, hence 4 drives. The confusion is mainly caused by the term IDE which is used and abused for other specs. I'm trying to put the definit answers in the TechNotes.
  • chucksterchuckster Junior Member Member Posts: 20 ■□□□□□□□□□
    Thanks for the information, seems like there is a lot of conflicting information out there especially when it comes to windows amd dos. Good to know that there are poeple like ya'll to help sort all this information into somthing usefull.
    Your gratefull student
  • SartanSartan Senior Member Inactive Imported Users Posts: 152
    Glad to be of help :)
    Network Tech student, actively learning Windows 2000, Linux, Cisco, Cabling & Internet Security.
  • DrakonblaydeDrakonblayde Senior Member Member Posts: 542
    Main thing to remember about the A+ (and Net+ for that matter) is to keep it simple and not overthink it. The A+ is going to try to test knowledge that is more or less current, and the de facto standard is that IDE, whether labelled EIDE or not, supports two channels, 2 devices per channel. I'm fairly certain no one is producing mobo's with IDE controllers that only support one device per channel anymore :)
    = Marcus Drakonblayde
    ==[X]===[X]====[ ]=====[ ]====[ ]==
  • WebmasterWebmaster Johan Hiemstra Admin Posts: 10,292 Admin
    The IDE TechNotes are online and can be found here:

    Regarding some comments in the above posts:

    Western Digital did develop EIDE, it is not an official standard though, it is/was a marketing term for the official ATA-2 specification. Similar unofficial standards called FASTATA and FASTATA-2 were the marketing names for ATA-2 of Seagate and Quantum. Seagate, Quantum and most other hard disk drive manfacturers stopped using the term IDE and EIDE and started using the proper term ATA. Western Digital still uses the term EIDE for standards way beyond the original unofficial EIDE standard. Western Digital did play a mayor part in the development of, mostly previous, ATA/IDE standards and new features but was not solely responsible for developing IDE nor Ultra DMA.

    Drakonblayde is right, when it comes to CompTIA exams you should go with the obvious overall opinion. At the time IDE supported 1 drive it was hardly a standard, some implementations did support 1 drive, others 2. The first IDE standard (ATA-1) did provide support for only 1 ide controller, hence maximum of two devices. EIDE (later combined with features of other unoffical specs into the official standard ATA-2) added support for a 'primary and secondary' controller, each 2 devices, hence a maximum of 4 devices in total.

    During my research for the IDE TechNotes I found a lot of conflicting documents, especially about who did what and when and how should it be called. I ended up using primarily official docs from several industry work groups involved in developing the ATA specifications, including an e-mail from the editor of the original ATA specification documents describing the real history of ATA/IDE.

    If you want more information than what is in the TechNotes, which should be sufficient for the A+ core exam, on the different standards, organizations and the history of hard disk drives and interfaces try and the links at the bottom of the TechNotes.
  • chucksterchuckster Junior Member Member Posts: 20 ■□□□□□□□□□
    Thanks for the link Webmaster, When you poeple answer a question it is plane to see that every effort is being expended to find the right answer to clear up the matter and I for one am very appriciative of all the effort put into this site.
    Hope to take both test in April and if I pass it will be because of your effort and care of all questions asked here.Keep up the good work and know that you are very appriciated here.
    Thanks All
  • WebmasterWebmaster Johan Hiemstra Admin Posts: 10,292 Admin
Sign In or Register to comment.