SCSI to IDE adapter... So Expensive, why?

Discussion in 'PowerPC Macs' started by poiihy, Dec 25, 2014.

  1. poiihy macrumors 68020

    poiihy

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    #1
  2. weckart macrumors 68040

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  3. Bug-Creator macrumors 6502

    Bug-Creator

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    #3
    Very few people needed these when SCSI was still relevant in the 90s and even less need thme today.

    Those few that did and do need them, are often willing to pay a higher price for whats most likely NOS items.

    Some time ago some user if a different forum organized a bulk purchase of SCSI-CF adaptors from China, and AFAIK we cleared out all his stock.
     
  4. rigormortis, Dec 25, 2014
    Last edited: Dec 25, 2014

    rigormortis macrumors 68000

    rigormortis

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    #4
    scsi is dead

    put a fork in it

    nobody needs scsi

    scsi was great because you could chain 15 hard disks and it would run off 1 irq channel. unlike pata and sata that uses 2 hard drives per IRQ.

    i don't know of anyone in the pc / mac world who are running out of IRQs

    i looked at my i7 windows device manger and i see irqs in the 190 range.

    we used to have only 15. before the ibm AT we had 8



    if you needed a lot of hard disks and you had a low number of irqs , that is why you went scsi

    if you want to build a tower and you want more then 4 hard disks internally, then you probably want scsi

    i think sata blows way uw scsi, last i heard scsi was like 160 megabits per second which is slow compared to the sata and usb 3 , firewire and tunderbolt controllers we have now

    Scisi was cool cuz it had " bus mastering " but even our sata buses do that now

    the only 2 reasons why scsi is expensive is because
    1) nobody needs it or wants it anymore so the sales are very low
    2) the drives might be "enterprise" meaning they have 5 year warranties where regular hard disks have a 1 to 3 year warranty

    the only real hardware advantage i can think of with scsi that might be still cool today, is you don't need to boot your os x cd to erase the hard disk, because you can do that in hardware with the hard disk controller.

    what are IRQs?

    irqs are interrupt request lines. each device in your computer took up an IRQ, the lower the irq was
    the higher priority it had, each time a device needed attention, it stopped the cpu from doing work


    each device, say cpu, math coproessor, floppy disk controller, hard disk controller video card, serial ports, parallel ports, sound cards, keyboard, mouse, USB controllers,
    these all take up precious irqs.
    you can't have a sound blaster on the same irq as your dial up modem
    in some situations, if you wanted a killer sound card you had to disable one of your computer's serial ports

    because of plug n play and irq steering, we don't even know what devices are on irqs, anymore
    nobody cares that your sound card is on IRQ 5. because we have so many of them, and the operating system takes care of them.


    if you want to say macs are superior to windows because irq's aren't used thats fine, that just shows you how dead and unimportant scsi is, i am pretty sure that macs use irqs because of maybe its still in x86 processors, but they don't even show up in system report. i tried looking for them!
     
  5. catzilla macrumors 6502

    catzilla

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    #5
    Perhaps for legacy embedded control systems, the same reason they still make floppies.
     
  6. rigormortis macrumors 68000

    rigormortis

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    #6
    i think 7-eleven stores is the only company left in the world still using scsi
     
  7. AlecZ macrumors 65816

    AlecZ

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    #7
    Stuff that almost nobody wants is often expensive because if someone does want one, he's probably desperate.
     
  8. bunnspecial macrumors 603

    bunnspecial

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    #8
    Isn't SAS(Serial Attached SCSI) still pretty typical in enterprise-class drives?

    I know that in terms of speed it's comparable to SATA, but does have some advantages over SATA such as hot swapping.

    Incidentally, for those of us who like to play with old Macs(mostly as a hobby in my case) some knowledge of SCSI as well as some spare parts is essential. I'll also add that I reguarly use a SCSI slide scanner that works wonderfully and is very fast. The fact that it's SCSI is also the reason why this particular model scanner sells for a pittance($20-30) compared to its USB or Firewire contemporaries, which still bring a couple hundred dollars on the used market. OS X Tiger+Viewscan(3rd party scanner software) make for a scanner that "just works".
     
  9. poiihy thread starter macrumors 68020

    poiihy

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    #9
    In what?
     
  10. rigormortis macrumors 68000

    rigormortis

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    #10

    my nas is sata and it supports hot swapping

    ----------

    the back room computer that runs 7-11 store operating system runs on a scsi based desktop computer,
     
  11. weckart macrumors 68040

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    #11
    Very much so. SCSI is anything but dead except for the consumer computer sector.
     
  12. happyfrappy macrumors 6502

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    Location eh?
    #12
    Comcast(former MediaOne/AT&T Broadband markets) still use Amiga 4000 for community television broadcast station tasks(EGA text updates) and for broadcasting 320/480p community shows/school sports which are run from a SCSI HDD array... in some areas they started a PATA to SATA conversions. Its amazing the amount of money Comcast donates back to towns they never switched 'em to G4 Mac minis to use PPC AmigaOS 4 or MorphOS which would allow keeping Toaster in action for another 10-15yrs and be able to use FW400 SATA multi-drive bay solutions :eek:
     
  13. goMac macrumors 603

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    #13
    There is some confusion here.

    Hardware IRQs still exist. There are only 16 of them on modern Intel machines. Mac and Windows machines both have them, but if you buy any computer made since the 486, they've been replaced in favor of APIC.

    With newer buses like PCI and USB, nothing is talking directly/interrupting the CPU any more and the IRQ is now obsolete. Stuff like your sound card talks to your CPU through the PCIe bus, not an IRQ.

    What you're seeing in Windows are virtual IRQs. Even though IRQs in the CPU are gone/no longer used really, Windows is still attached to the concept of IRQs to keep the operating system going. So, they created virtual IRQs. They don't mean anything in the hardware. They're basically Microsoft keeping old source code working.

    On the Mac side you never see this because there isn't any legacy to deal with like there is in Windows.

    So basically, yes, SCSI is still kind of silly these days, but for a totally different reason. You don't have to worry about IRQs because no modern chipset made in the last several decades has it's features linked to an IRQ.

    The idea of peripherals actually having interrupt privileges went out of style long ago, about the same time Star Trek the Next Generation went off the air. It's trouble for modern OSs.
     
  14. rigormortis macrumors 68000

    rigormortis

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    #14


    the fact that IRQ isn't even used anymore like you say, simply just puts the final death nail into Scsi. there is simply no reason anymore to use it

    had their been real irqs since the 486, we would of had a legitimate reason to run scsi
     

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