[comp.sys.amiga.hardware] hard drive controller definition; 14mhz motorola chip

dtiberio@libws3.ic.sunysb.edu (David Tiberio) (11/30/90)

IVS or ICD just announced a 14mhz 68000 chip in the current Compute!. It has
a standard 7 mhz software switchable option.


What is a SCSI controller?

It usually handles 8 hard drives. It allows some hard drives to autoboot.
It often contains on board ram to be used as a buffer or cache. It may also
work with DMA, which means that it may or may not slow down other programs
that are multitasking when the drives are accessed. Many controllers often
have sockets or SIMMS for up to 8 megabytes ram. The type of controller as
well as the drive speed will make programs load faster or slower. Many
controllers also provide a place to mount the hard drive; otherwise you 
would have to use a disk drive bay (on a 2000/3000). I hope that this info
is helpful in your search for a hard drive, and if any info is incorrect
please feel free to tell us. :)

David Tiberio  SUNY Stony Brook 2-3605  AMIGA  Toto Productions  DDD Men

ben@epmooch.UUCP (Rev. Ben A. Mesander) (11/30/90)

>In article <1990Nov29.185824.1990@sbcs.sunysb.edu> dtiberio@libws3.ic.sunysb.edu (David Tiberio) writes:
>What is a SCSI controller?
>
>It usually handles 8 hard drives.

Almost. The SCSI bus allows 8 devices. Since the controller is one device on
the bus, it can only have 7 drives hooked to it. There are allowances for
extending this via having several devices hooked to different logical units
on a single SCSI device, but these are usually not used.

>David Tiberio  SUNY Stony Brook 2-3605  AMIGA  Toto Productions  DDD Men

--
| ben@epmooch.UUCP   (Ben Mesander)       | "Cash is more important than |
| ben%servalan.UUCP@uokmax.ecn.uoknor.edu |  your mother." - Al Shugart, |
| !chinet!uokmax!servalan!epmooch!ben     |  CEO, Seagate Technologies   |

lphillips@lpami.wimsey.bc.ca (Larry Phillips) (12/02/90)

In <ben.3630@epmooch.UUCP>, ben@epmooch.UUCP (Rev. Ben A. Mesander) writes:
>>In article <1990Nov29.185824.1990@sbcs.sunysb.edu> dtiberio@libws3.ic.sunysb.edu (David Tiberio) writes:
>>What is a SCSI controller?
>>
>>It usually handles 8 hard drives.
>
>Almost. The SCSI bus allows 8 devices. Since the controller is one device on
>the bus, it can only have 7 drives hooked to it. There are allowances for
>extending this via having several devices hooked to different logical units
>on a single SCSI device, but these are usually not used.

Pong! (the sound of the puck hitting the post)

Close. The SCSI bus allows 8 devices. Since the controller is one device, it
can have only 7 other _devices_ hooked to it. Drives with embedded controllers
can usually only handle the single drive they are part of, but there are _many_
controllers that will handle more than one logical unit. Some will handle two,
some will handle 8. A very few will handle more (there is provision for up to
256 drives per controller).

Don't know what you mean by 'usually not used'.  Of the four controllers
attached to my 3000, two of them are embedded in drives, with no provision for
adding more drives, and the other two allow 2 drives per controller.

-larry

--
The only things to survive a nuclear war will be cockroaches and IBM PCs.
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