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Thread: SCSI?

  1. #1


    To whom who use Scsi,
    I would like to upgrade my system to scsi components. Such as hard drive, cdrw, and scanner. I have done a little research. I am just astounded by all the different options. I ask for your help. Scsi is expensive. I wouldn't want to make any mistakes.
    1.Which type of scsi is the best, such as scsi2, ultra 160, scsi3,ect?
    2. Should firewire be a option?
    3. What controller card should I buy?
    4. What should I look for in a hard drive?
    5. What amount of buffer should the hrd drive have?
    Any additional info would be a great help.

  2. #2


    The following, taken in itís entirety, from PC Mechanic.

    The popularity of SCSI is increasing rapidly, but I believe this is due to a misunderstanding. It is often thought that SCSI automatically blows IDE away when it comes to performance. While SCSI does offer a faster throughput, one's activities on the machine affect just how much this performance will really matter. Several factors must be considered when determining which is better for you.
    Most PC's use IDE drives because they are cheap and they perform well. But, to look at performance, you need to look at the entire drive.
    Many manufacturer release identical model drives in both IDE and SCSI formats. If you look at these drives, they are identical except for the logic board. This means that the HDA and other drive mechanics are the same. The difference lies in the logic board. The IDE logic board has the disk controller and the built on AT bus interface. The logic board on the SCSI drive contains one extra SBIC chip. Basically, this chip is a SCSI adapter to allow the drive to operate on a SCSI bus. So, structurally, IDE and SCSI drives are the same.
    The performance overhead of SCSI over IDE comes from structure of the bus, not the drive. The nature of the SCSI bus allows it much better performance when doing data hungry tasks such as multi-tasking. The SCSI bus controller is capable of controlling the drives without any work by the processor. Also, all drives on a SCSI chain are cable of operating at the same time. With IDE, one is limited to two drives in a chain, and these drives cannot work at the same time. In essence, they must "take turns".
    In some computers, SCSI is better. As mentioned above, SCSI is a smarter bus than IDE. There are many steps in the SCSI data transfer. But, on OSes that allow multitasking, or if you often use several programs at once, the SCSI drive is a better choice because this extra intelligence of the SCSI bus is used.
    SCSI devices can communicate independently from the CPU over the SCSI bus. This is due to the fact that each device has its own embedded controller. Data can then be transferred at high-speeds between the devices without taking any CPU power. IDE, likewise, uses controllers on each device, but they cannot operate at the same time and they do not support command queuing.
    Last Thoughts
    Finally, let me say that for most people, IDE is just fine and offers very good performance. The reason I believe one does not need to get SCSI, though, is that most users do not use their system in a way that would actually justify the SCSI bus. While the nature of the bus is faster, it takes certain situations to actually need it. Couple this with the significantly higher price; one can see that they can easily live with IDE.

  3. #3


    The article above pretty much covers the IDE vs SCSI vs Price debate but there are a few things I don't quite agree with. Nowadays SCSI and IDE drives are no longer the same drive with different electronics. At least the vast majority of drives no longer are. The average SCSI drive today has a rotational speed of 10,000rpm, access times of ~5ms and regularly around 4 megs of cache. You will not find a single IDE drive like that and those are the three most important factors in harddrive speed. By the end of the month we will also have drives with 15,000rpm speeds seek times of less than 4ms and cache sizes of 16megs. You WILL notice the difference in speed no matter what. While IDE would seem to be comming close to SCSI territory with new standards like ATA100, this is a very big misconception. The controllers bandwidth has very little to do with drive performance. No single IDE drive can even come close to maxing out a 33mb/s channel let alone 66. The only possible way to reach this would be by RAID 0'ing the drives and even still its a lot of headroom. The drive's cache will also benefit from being able to transmit data through the bus faster but that isn't such a big deal with IDE drives due to its limitations. Cache will benefit SCSI drives much more than IDE due to the way they work. The whole point of cache is that it can store data there while the drive or some other device can perform another task or command and then write or send the data on the cache. This works perfectly well for SCSI drives which support out of order command quieng "scatter gather" and such features. On IDE drives however cache will not be quite as usefull. Since the IDE bus needs to hold the device locked down until a command is complete before moving on to the next the cache won't really fulfill the same purpose as it does in a SCSI bus. I still think most people don't need SCSI. But if you want the extra bit of speed and don't mind the cost or are just a regular tweak freak and just like everything to go as fast as it can I'd say go for it.
    To answer the original questions:
    1)Go with the latest obviously, Ultra 160

    2)For harddrives its not worth it, SCSI 160 is faster.

    3)I think so far the only consumer level Ultra 160 card is the adaptec series. You can get the low end 19160 which is the cheapest if you have no old SCSI devices you want to keep plugged in. It brings a 68pin LVD (80/160mb/s) plug and one 50pin UltraSCSI(20mb/s) plug for older or slower devices like CD-ROMS. If you want full connectivity get the 29160 which has plugs for everything. I know all these connectivity standars and how they are compatible between each other can be quite confusing but if you'd like me to explain it all in detail just let me know and I'll be glad to answer your questions.

    4)10,000rpm, ~5ms seek times, and 4 megs of cache should be the least you should settle for if you really want to notice the difference.

    5)Refer to number 4.

    If you are buying SCSI peripherals go to:
    It is the ONLY place to buy SCSI for cheap unless you don't mind paying an arm and a leg for it. They have the adaptec 19160 for as low as $150 and the 29160 for around $199. Their service is also excellent.

    [This message has been edited by El Diablo (edited 06-09-2000).]

  4. #4

    Thumbs up

    El Diablo, Thx. That was the kind of response I was looking for. I wish more users would give a direct answer. When I read the above it made absolutely no sense. I mean, just looking at the specs. between a IDE drive and Scsi, they are no where similar.

  5. #5


    Is there a reason that you want to go SCSI? although SCSI drives do have higher performance then IDE drives nowadays, the high end IDE drives are almost as fast as SCSI drives. and the price gap is really big. SCSI benefit from the controller taking care of your I/O to the subsystem, therefor free up the CPU to do other things, and since it can simultaneous control serveral devices, it also speeds up the overall system access. and yet SCSI gives you more devices per system (15 vs 4 in most cases).

    Although Ultra160 sounds impressive, but the actual transfer speed from HD to computer is still limit by your drives physical attribute, rotation speed, platter density, and number of platters. If you only have a 1 or 2 drives connect to the Ultra160 bus, it'll probably proform as well as it's connected to a UWSCSI bus, since the overall bandwidth is still less then the theoritical bandwidth of the bus. but if you are doing a RAID(which is almost a SCSI only configuration), multiple drives read/write across a single bus will benefit from much higher bandwidth of the Ultra160 bus.

    nowadays the drive and device makers tend to make the SCSI drives slightly more advance then their IDE counterpart, such as the rotation speed, buffer, and size(but now IDE has caught up most of them). CDRW also tend to benefit from SCSI bus, since it reduce the chance for buffer underruns, and you no longer need to wait the computer to finish CD burning before you can use the computer..

    but SCSI is also a lot of pain in the butt to maintain. you'll need to spend quite a bit amount of money on the controller card, drives, cables, and terminators. AND cooling fans for those 10K rpm drives... and yes, you need to cool those high rpm drives, other wise they'll self destruct due to thermal problems.. luckily for me, I only blow one of my Micropolis and SCSI are a lot harder to configure then IDE drives, you'll need to get the concept right, and spend sometime to trouble shoot your setup before everything is up and running..

    IMHO, it's worth your money to spend on SCSI system, IF you do a lot of disk I/O related stuff, like recording videos, video editing,
    animation and such... since your hard drive IS the slowest component of your system.....

    as for Ultra160 controllers, all you need is Adaptec 19160, if you don't plan to run Linux, SCO, Novell on your system. since 19160 supports Win9x and NT only. otherwise you'll need 29160N for the compatibility on other OS. 29160 is 64bit PCI instead of 32bit on 19160 and 29160N, so unless you have one of those in your MB(unlikely), don't bother. 39160 has 2 Ultra160 channels for 30 devices total. All of the adaptec cards have both 68pin and 50pin connectors so you can connect almost anything to it.(except HVD drives)

    as for drives, if you can afford and have the need, go for the current generation Seagate Cheetah 10K rpm drives.. they are still the best. Quantum Atlas 10K and IBM 10K drives are slightly behind in performance, but not much... and they cost less, too. but you'll need cooling on those drives... 7200rpm drives are not bad, either. and they don't require active cooling(fan).. although I still do on mine system. If you truely need the access time and transfer speed, go for a RAID solution and stack all your HDs together.

    if you need more information, go to

  6. #6


    <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by esung:

    as for Ultra160 controllers, all you need is Adaptec 19160, if you don't plan to run Linux, SCO, Novell on your system. since 19160 supports Win9x and NT only. otherwise you'll need 29160N for the compatibility on other OS. 29160 is 64bit PCI instead of 32bit on 19160 and 29160N, so unless you have one of those in your MB(unlikely), don't bother. 39160 has 2 Ultra160 channels for 30 devices total. All of the adaptec cards have both 68pin and 50pin connectors so you can connect almost anything to it.(except HVD drives)

    The 29160 has a 64bit PCI connector but is backwards compatible and can plug into a regular 32 bit slot. The advantage it has is an extra UltraWide connector. This could be a necesity in some cases if you need to keep 68pin Single Ended devices connected (HVD (high voltage diffrential) devices are rarely used and require a specialized adapter like the 2944UW so don't expect to see many of these around). Otherwise you would have to connect the SE devices to the 68pin LVD connector on a 19160/29160N bumping down all devices to 40mb/s.

    Cooling is also an important issue with these harddrives but active cooling for them is NOT a neccesity. As long as your case in general is well ventilated and keeps a flow of cool air coming in(usually not a problem among the overclocking/tweaking crowd ) you will be fine.

    [This message has been edited by El Diablo (edited 06-11-2000).]

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