hans@ele.tue.nl (& Fleurkens) (07/13/90)
I'm interested in information about hard disks, hard disks controllers such as: - MFM - RLL - SCSI - .... Please let me know where to get information about this subject. Thanks in advance. Juraj. ------- Juraj Zelenay Eindhoven University of Technology The Netherlands E-mail: hans@es.ele.tue.nl
grege@gold.GVG.TEK.COM (Greg Ebert) (07/16/90)
In article <HANS.90Jul13125225@eutes4.ele.tue.nl> hans@ele.tue.nl (& Fleurkens) writes: > >I'm interested in information about hard disks, hard disks controllers >such as: > >- MFM >- RLL >- SCSI MFM (Modified Frequency Modulation) This is the standard encoding technique for hard disks, and double-density floppy diskettes. The majority of the hard disk controllers are MFM. Data transfers to/from the controller are I/O read/write cycles. RLL (2,7 Run-length limited) - A data compression technique which uses narrower data windows to increase the recorded bit density by 50%. As far as the PC is concerned, it doesn't care if you use RLL or MFM, except that you will have more storage with RLL. SCSI (Small Computer System Interface) Originally developed by Shugart for hard disk interfacing, but now applicable to tape, etc. The only SCSI board I have used is made by Adaptec. It plugs into the AT and becomes a 16-bit master. Data transfer is faster than the I/O mapped MFM and RLL controllers, but this is only an important issue for UNIX or server applications. Not surprisingly, higher performance cost more.
jarvi@plains.UUCP (Trent Jarvi) (07/17/90)
In article <1171@gold.GVG.TEK.COM> grege@gold.GVG.TEK.COM (Greg Ebert) writes: >In article <HANS.90Jul13125225@eutes4.ele.tue.nl> hans@ele.tue.nl (& Fleurkens) writes: >>I'm interested in information about hard disks, hard disks controllers > >MFM (Modified Frequency Modulation) This is the standard encoding technique for /* Standard but works */ > >RLL (2,7 Run-length limited) - A data compression technique which uses narrower /* more diskspace */ > >SCSI (Small Computer System Interface) Originally developed by Shugart for hard /* $ and fast; breakfast of champs */ Could you be so kind as to exlain what an IDE is? The dealer said it was mumbo*NEW*mumbo*FAST*mumbo*jumbo Should have heard the HMHMwarntyCOUGH that went with it :)
grege@gold.GVG.TEK.COM (Greg Ebert) (07/17/90)
In article <5307@plains.UUCP> jarvi@plains.UUCP (Trent Jarvi) writes: > >Could you be so kind as to exlain what an IDE is? >The dealer said it was mumbo*NEW*mumbo*FAST*mumbo*jumbo > > IDE - Integrated Drive Electronics. Wow!!! Conner Peripherals put *ALL* the disk controller logic (data separator,serial<->parallel,buffering,etc) onto the drive itself. An IDE drive only needs a trivial interface card, which some manufacturers build into their motherboards. The ASIC I designed at AST Research had IDE support on it. If you get a system with an internal IDE interface, all you add is the drive and a 40 pin connector. No more hard disk controller board. IDE drives are upward compatible from the 16-bit AT style controllers and are software-transparent to DOS, etc. Why get such a drive ? Well, you'd NEVER, NEVER wan't to replace an existing AT controller with an IDE setup, because you gain nothing. My guess is that IDE drives were created for portable systems with tight power and slot-count requirements. Also, you wont get the performance of an ESDI/SCSI controller. Now, if you're a hardware hacker and want to add a hard-disk to some sort of specialty equipment, this beast is the answer to your prayers.
cjp@beartrk.beartrack.com (CJ Pilzer) (07/17/90)
The IDE interface is also sometimes called the AT interface. The actual controller is built into the disk drive and a very simple host board is but in the buss slot. The host board merely sends signals between the buss and the drive. All the smarts are in the drive. This should allow for really good transfer of data since the controller can be matched closely to the drive. It also allows for some economies in production. Such combinations could be either faster or slower than other interfaces. I think that most present implementations are faster than MFM and slower than ESDI. Since the host adapter is so simple it is sometimes built right into the motherboard. -- cj
hans@ele.tue.nl (& Fleurkens) (07/17/90)
Thanks for the information about this subject, but I should specify my request more clearly. Does anybody know books, articles, magazines about hard disk controllers & hard disks in general? An introduction on this subject would be very useful. ---- Juraj Zelenay Eindhoven University of Technology --- E-mail: hans@es.ele.tue.nl
kleonard@gvlv1.gvl.unisys.com (Ken Leonard) (07/17/90)
In article <1174@gold.GVG.TEK.COM> grege@gold.GVG.TEK.COM (Greg Ebert) writes:
*
* IDE - Integrated Drive Electronics. Wow!!! Conner Peripherals put *ALL* the
* disk controller logic (data separator,serial<->parallel,buffering,etc) onto
* the drive itself. An IDE drive only needs a trivial interface card, which
* some manufacturers build into their motherboards.
*
* The ASIC I designed at AST Research had IDE support on it. If you get a
* system with an internal IDE interface, all you add is the drive and a
* 40 pin connector. No more hard disk controller board. IDE drives are upward
* compatible from the 16-bit AT style controllers and are software-transparent
--
Interrogative compatible what way? As in commands? As in cchhss address?
As in lowlevel format? As in badtrack handling?
--
Will a lowlevel disk manager program (like SpeedStor or DiskManager) see
the same things as with an MFM drive? Will a diskmanager stiil be useful
for partitioning (for DOS 3 or multiboot systems?) Will a diskmanager
still be useful for surface scan, etc?
-----
I think I need to know, because I'm _soon_ to buy a system and need to make
a choice.
----------
regardz,
Kengrege@gold.GVG.TEK.COM (Greg Ebert) (07/18/90)
In article <816@gvlv2.GVL.Unisys.COM> kleonard@gvlv1.UUCP (Ken Leonard) writes: {stuff about IDE deleted} >-- >Interrogative compatible what way? As in commands? As in cchhss address? >As in lowlevel format? As in badtrack handling? >-- >Will a lowlevel disk manager program (like SpeedStor or DiskManager) see >the same things as with an MFM drive? Will a diskmanager stiil be useful >for partitioning (for DOS 3 or multiboot systems?) Will a diskmanager >still be useful for surface scan, etc? >----- >I think I need to know, because I'm _soon_ to buy a system and need to make >a choice. >---------- IDE is 100% upward compatible with the AT controller. I have personally removed an AT controller and replaced it with an IDE interface, and ran a low-level format. My friend Rich wrote BIOS code at AST and he says there is no difference between AT and IDE controllers at the BIOS level. If you're buying a system, don't pay more for an IDE interface if you have an ample number of slots and you intend to use your old hard-disk controller. The only advantage of IDE is it allows 'no-slot' hard-disks -- great for luggables and tiny desktop systems. If you are looking for high-performance disk operations, try an Adaptec SCSI/ESDI controller. Also, IDE drives cost a few more bucks, so don't expect to save money. As far as SpeedStor/surface-scan/etc, shit I dunno, man. I'm a hardware nut. I think it's safe to assume that these [bomb-code] packages will run ok. Clarification: MFM is a data encoding technique frequently used on hard/floppy disk drives, and can be used in AT, IDE, and SCSI controllers, as well as RLL encoding. So, when someone says 'I have an MFM controller', it could be IDE, AT, or SCSI/ESDI.
efb@suned1.Nswses.Navy.MIL (Everett F Batey) (05/05/91)
Thanks for the thread to get on. Been debating SCSI on my DTK-386-20 for some
while. DOS 3.3 (yeah 32MB). Presently have TWO RLL 60MB HDs and one each 1.2
and 1.44 FD, four (4) drives, 2HD+2FD.
The questions:
- CAN I ADD SCSI disk beyond my 2+2 without doing the IRQ war ?
-- ( I need to save an IRQ for being a network [TOPS] server, later. )
- If so, WHAT impact will there be on my existing disk controller ?
- What grief will I have utilizing SCSI H:, I:, J:, K:, L:, ... drives and
exporting them over a network, like TOPS ?
--
+ efb@suned1.nswses.Navy.MIL efb@gcpacix.uucp efb@gcpacix.cotdazr.org +
+ efb@nosc.mil WA6CRE Gold Coast Sun Users Vta-SB-SLO DECUS gnu +
+ Opinions, MINE, NOT Uncle Sam_s | b-news postmaster xntp dns WAFFLE +davidsen@sixhub.UUCP (Wm E. Davidsen Jr) (05/07/91)
In article <9658@suned1.Nswses.Navy.MIL> efb@suned1.Nswses.Navy.MIL (Everett F Batey II) writes: | - CAN I ADD SCSI disk beyond my 2+2 without doing the IRQ war ? | -- ( I need to save an IRQ for being a network [TOPS] server, later. ) IRQ is not used by DOS, so you should not have a problem with it. However, in case you want to run UNIX later you want a 16 bit controller which can do interrupts on the "high" IRQs. I *think* Adaptek does this, and they make a controller with no floppies, or used to. -- bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen) sysop *IX BBS and Public Access UNIX moderator of comp.binaries.ibm.pc and 80386 mailing list "Stupidity, like virtue, is its own reward" -me