Tech Question: why only 2 ide controllers?

[DiseasedDonkey]

I am really confused. Why are mobo manufactures limiting the amount of controllers to two. i am sure the bios is to blame, but is there anyting out there or in the works so i can have more than 4 ide (NOT SCSI) drives on one computer? Why is there still this stupid limitation? What is the rational?

Does anyone know of any mobo that support 6 or 8 ide drives? God knows i have a boatload of <10 gig HD's lying about

 

[ComputerAce]

I don't know why, but there is only two IDE controllers with 2 devices max on motherboards. There are none out there that have more. I used to know the answer to this, but I forgot. I think it has something to do with IRQ's. - but then again, I could be wrong.

Cory

 

[Brian23]

The motherboard's chipset comes w/ 2 channels. Some mobos have an ATA66 or an ATA100 chip that lets you put up to 4 more drives in. PCs have 16 IRQs, but if you got a dual processor setup you get 16*16= 256 IRQs. (I think)

 

[Bloodybrain]

You don't get any more IRQs when you add CPUs. The architecture of the PCs since the 286 is made that way... you have 16 IRQs on the system bus. In fact you have 8 but IRQ2 is cascaded to another interrupt controller (internal to the chipset) which manages the 8 remaining IRQ... that's why IRQ2/9 is the same IRQ.

 

[Noriaki]

There are lots of mobo's that have more than 2 IDE connectors.
There are no chipsets that I know of..I'm not entirely sure why that is.

IRQ's are hard to come by, here's an example:

0 - System Timer
1 - Keybaord
2 - Cascade to upper 8 IRQs
3 - COM2/4
4 - COM1/3
5 - Soundcard
6 - Floppy
7 - LPT1
8 - RT Clock
9 - PCI Slot (as mentioned, 2/9 are attached, you can't use both)
10 - USB
11 - PCI Slot (Edit: This is actually my AGP slot..close enough )
12 - PS/2 Mouse
13 - Floating Point Unit
14/15 - IDE

I have both com ports disabled so that gives me 2 more...
In my case my IRQ4 is used for a PCI slot as well. One PCI slots shares with my USB, and my soundcard uses 5 &amp; 9
If I disabled dos support sound, I could fit in another IDE controller on 3 &amp; 5, but in a typical setup it's hard to find IRQs to fit everywhere and even PCI cards can be pretty picky about sharing, and ISA devices (COM ports &amp; PS/2 ports are ISA devices) are very unfriendly about sharing, but most systems default to having two COM ports on so they don't have the IRQs

IRQs are pretty tight resource..
but if you want more IDE channels on your system just pick up a Promsie Ultra66 and you'll have an extra channel or two (you can enable only 1 or both) provided you have the IRQs for it.

SCSI fits 15 devices on a single IRQ, IDE fits 2.
But if you have the IRQs you can load up as many IDE channels as you want.

The Asus CUBX and A7V both have 4 IDE channels, as do any boards from ABit with a RAID controller built in, several Soyo boards...it's an option on the K7TMaster (though with onboard SCSI what the hell would you want it for?) There are boat loads of boards with 4 IDE channels.

 

[toph99]

why don't they just add more IRQ's?

 

[Brian23]

It has something to do with the way they designed the 286 processor. It would require the CPU to be redesigned, and then it might not be x86 compatible.

 

[Noriaki]

For the same reason that the P3 and Athlon can still run programs written on a 286. Like Brian23 said, if you make major changes you lose backwards compatibilty, if backwards compat. wasn't an issue AMD and Intel would most likely be making RISC based chips by now.
Instead of this sorta half/half RISC/CISC crossbreed we have now. Even an Athlon can't match FPU power with a G4 (a truly RISC based CPU)

 

[tonster]

I would like to agree that RISC processors are FPU friendly, however, because of the lower clock speeds, single tasking OS, and lack of support for gaming (which is primarily what FPU is used for), G4's lag behind. I would, however, like to see a new architecture. x86 should die soon. Sometimes you just have to give up on backwards compatibility and take a brave step forward (ie. Windows ME and it's inherent DOS problems). DOS gaming is dying, and with it, some excellent games, but the future is here.
One other note, the G4 is as much a CISC processor as the x86 is a RISC processor, nowadays.

 

[Zenmervolt]

First, Brian: Bill gates never actually said, &quot;640K of memory is enough for anybody&quot;. It was a paraphrase taken out of context. What he actually said was something to the effect of there having been nothing on the software market at the time that needed more than 640K of memory. As for the controller issue, why does anyone need more than 4 IDE drives on a basic system (2 drives per channel)? Anyone using more drives will probably invest in a dedicated controller card for greater speed and stability. Look at things realistically here, with 75GB IDE drives availabe, 2 IDE controllers provide for 150GB of HDD space while still allowing a DVD-ROM drive and a CDRW drive to be installed as well. Anyone needing more than this would be likely to go SCSI. I can understand it in a situation where there are backup drives (ZIP or DAT) necessary as well, but on a system with a DAT drive it is unlikely that a DVD-ROM drive is necessary, and with USB available, external ZIP drives are so close in speed to the internal ones that I can't imagine giving up the portability of my 250 USB for the extra 0.001MB/Sec in transfer speed. Then there's the issue of available room in the case as well as just how good a power supply do you need to power 4 drives plus an Athlon or PIII plus an AGP graphics card plus 2 128MB SDRAM DIMM's plus... Four drives seem to be to be just about the practical limit when dealing with basic system and I really can't imagine needing more. (Wanting more is another matter altogether.)

Aaron Meyer

 

[Noriaki]

Fair enough tonster, I never meant to imply I think that Mac is a better platform, I think Mac is a horrid platform, I happen to think the G4 is a very nice CPU for it's speed. Compared to an Athlon/P3 at the same clockspeed at least in FPU power, the G4 is pretty powerful.

There are all sorts of limits outside the CPU, I meant CPU only. I wasn't comparing platforms.

 

[Linh]

Would power become and issue with more than 4 drives?

 

[tonster]

I guess I just take it the wrong way when someone says ANYTHING positive about a macintosh You are right, though, RISC processors do inherently have better FPU. I am not sure that would be enough reason in and of itself to turn to RISC though. Integer operations are important in everyday Windows apps; the area where most users spend most of their time. We'll just have to armchair quarterback until Intel and AMD make the plunge into a new architecture.

 

[Noriaki]

<< I just take it the wrong way when someone says ANYTHING positive about a macintosh >>

I can understand that I almost put that reply post as a footnote of the origianl one just for that reason. I feel much the same way. Hehehe Personally I find that my computer providing me with 60fps in Q3 1024x768x32 HQ maxed is fast enough, I don't find myself in need of a faster FPU yet. So I'm not about to jump ship to the mac hehe