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Thread: Different ATA Buses in G4/1250 MDD

  1. #1
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    Default Different ATA Buses in G4/1250 MDD

    The Powermac G4/1250 Dual MDD comes with dual ATA buses: one ATA/100 bus and a second ATA/66 bus. One ATA100 /160 GB hard drive is preinstalled, with a ribbon cable available for connecting a second drive. The ATA/66 bus can also connect to two hard drives.

    Why two buses? And why different? Moreover, is it true that the disk on the second bus (ATA 66) will be not bootable on OS9?

    Anyway, I'd like to add a second 160 GB HD but the question is: where? Transfer dates in the two disks will be faster installing the second disk on the same bus of the original disk (ATA 100) or in the slower bus (ATA 60)?

    In the second case, are still available ATA 66 disk? I did not find them on line. I need one of them also for another old G4.

    Thanks.
    gg

  2. #2
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    Having the extra bus or channel is like adding a PCI controller. ATA 66/100/133 are all interchangeable. You can put an ATA 100/133 on the ATA 66 bus. Many people like to partition a drive so their System/Apps are on one drive and data on another this way both can be accessed at the same time at full speed. Makes backups easy too. A system on both drives using the remainder for your data and backups on the other - one system for emergency/repair/etc. A good ATA or SATA drive can get 50mb/sec. So putting 2 drives on the same pipe/bus/channel just congests issues.

    I dont see why and have not heard of talk that the ATA 66 will not boot OS 9.x -- Others will know for sure.

    What is your main use? This info can help you set things up for best performance. Others can be more detailed.

  3. #3
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    I think at one point OS 9 couldn't 'see' the ATA/100 actually. Both are fine. Faster to have one on each bus. The fastest ATA drive is 60MB/sec - under what either will do, but ATA doesn't 'share' a bus - when one drive is busy, the other has to wait. But if you have a drive just for storage, or media, fine. Copying bus to bus is faster than on the same bus, almost as bad as reading and writing to partitions on the same drive. Congestion.

    I'd say the G4 is nice in having 6 drive bays vs 3 for G5s.

    Before, users were adding PCI cards to add more drives. You still can ;-) if you want, SATA, or FW800 PCI card, or SCSI.

    I bought one of the "SP" models a couple months ago and still settling in but I have got three drives (two SCSI) along with Combo and SuperDrive and two SCSI controllers as well as Sonnet Tango (USB2 + FW).

  4. #4
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    Thanks to the Gurus and to the Senior member.
    At this point I have some doubts:

    • You say: "ATA 66/100/133 are all interchangeable." OK, but the speed bus will be as that of the slower disk? In other words, what if I have on a bus an SATA drive and a ATA drive on the other bus?

    • Ultra ATA and ATA are the same? ATA 6 and ATA 66 are the same?

    • Does a new SATA drive in a G4/1250 MDD (with a SeriTek/1S2 Host Adapter) work fine if the original ATA100 disks remains on the other bus? Or it's better to leave both the drives at ATA 100? I read that SERIAL ATA is a technology still not mature...

    • I work mostly with Photoshop. I think to make 3 partitions on the ATA 100 drive (OS9 + apps.; OSX+apps; work files ) and 2 partitions on the SATA drive (scrath and archive data). In this way when Photoshop reads an file from a bus it writes scratch data on the other bus at the same time. Moreover, I have an external FW drive with both the system 9 and X that I use for storage and troubleshooting.

    • What it means "master" and "slave" exactly?
    gg

  5. #5
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    It isn't that complicated, really ;-)

    Put one ATA drive on ATA/100 and ATA/66 (ATA/66 is under the optical drive bays). Put two SATA drives in there, same cage as the ATA drive, but on Seritek controller, so separate bus.

    Separate bus = no I/O "collisions"
    bus and disk speed are not limiting either
    two drives on same bus when reading writing to both slows down both when it is concurrent.

    Each SATA drive is on its own bus so they never get in each others way.

    The ATA/66 is harder to 'explain' as the MDD has native IDE support for ATA6 (or is it ATA7?) "large drive" support, drives >128GB.

    MDD doesn't use "master and slave" to jumper a drive. ATA/PATA drives have jumpers to set those. Cable Select (CS) does away with that and simplifies. However, with one drive, it should go on the black end connector and will be treated as "master' and terminate the bus. Slave goes in the middle. CS works all the way back to Beige G3's when using an IDE controller (ACArd, SIIG, Sonnet Tempo cards). Apple is clearing up, standardizing, and making things easier. OS X was a mishmash at first, not pure *nix standard on this issue. They have tightened standards on RAM, USB and other items as well.

    One of the options with SATA is 10K Raptor, one or two of those, while expensive, are also up there with 10K and 15K SCSI drives almost. In the SATA Reference thread in SATA/ATA/FW forum is a link to review comparisons of 10K drives and most of the major brands today. You might want to RAID a pair of SATA drives.

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    For an SATA drive you would need a SATA controller card in a PCI slot like the SeriTek. If the drives are on separate busses each drive will run at its max speed. Your best bet is to buy an ATA drive with an 8MB cache and put one on the 66 the other the 100. If your drive could read/write data faster than 60MB/sec than the ATA 66 might be slower but you wonÍt have a drive that fast. Unless you need more than 2 drives or a RAID.

    >>Ultra ATA and ATA are the same? ATA 6 and ATA 66 are the same? A good one for TZ

    >>Does a new SATA drive in a G4/1250 MDD (with a SeriTek/1S2 Host Adapter) work fine if the original ATA100 disks remains on the other bus? Yes no problems.

    >>Or it's better to leave both the drives at ATA 100? - Keep em separate.

    >>I read that SERIAL ATA is a technology still not mature... - There is no reason to purchase the extra SeriTek/1S2 Host - you have 2 busses. A good ATA drive with 8MB cache will perform just as well. Check the drive comparison database here... http://storagereview.com/comparison.html

    >>What it means "master" and "slave" exactly? - Like the old SCSI ID=0, ID=4 a way or method for you and puter to identify. Most people put one drive per bus as Master.

  7. #7
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    There is one instance where the Serial ATA controller makes sense: you use it for scrach using two SATA drives to get 110-140MB/sec. You can get twice that almost with SCSI but cost is "high."

    you would end up with four drives, each independent, on their own bus and controller.

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