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From: timothym@tekigm2.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Re: hard/floppy cntrllr f/IBM-PC
Message-ID: <1207@tekigm2.UUCP>
Date: Wed, 12-Nov-86 14:04:18 EST
Article-I.D.: tekigm2.1207
Posted: Wed Nov 12 14:04:18 1986
Date-Received: Sat, 15-Nov-86 04:49:12 EST
References: <2183@ecsvax.UUCP> <21900185@uiucuxc> <1179@tekigm2.UUCP> <129@gaia.UUCP>
Reply-To: timothym@tekigm2.UUCP (Timothy D Margeson)
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 48

In article <129@gaia.UUCP> zhahai@gaia.UUCP (Zhahai Stewart) writes:
>> A few more notes, ALL ST506 or ST412 disk drives use an 8 bit data path, an
>Actually, these drives and almost all 3.5" and 5.25" Winchester drives [EXCEPT
>THOSE USING RLL ENCODING LIKE THE SHUGART ST-238 WITH APPROPRIATE CONTROLLER]

ST506 and ST412 are current standards for hard disk interfacing, and were
developed by Seagate Technologies, Inc. The ST-238 disk drive is a RLL mode
drive manufactured and sold by Seagate Technologies as well, and uses the 
ST412 I/O convention.

I was wrong on the 8bit data path, single bit data IS sent across the data
cable, not the 8 bit path I described. SORRY for passing misinformation.

>use an instantaneous data rate of 5 Mbits/sec (625 KBytes/sec).  Counting the
>address and data marks, error correcting codes, CRC, and inter sector gaps,
>the sustained data rate cannot be much better than 1/2 MByte/sec within one

Probably a better estimate of data rate than mine.

>(Probably not tho - since his reccomended test used disk reads only, not 
>disk writes; be sure your test includes both if that write performance also

My method DID test read AND write performance (COPY both reads, then writes
to the hard disk, and does an additional read if VERIFY is on). Only the
actual running of programs performs only reads, which I suggested as a
secondary test.

>Also, all of these disks use a bit serial (not 8 bit) data path.
>Some controllers for the PC claim to be able to handle 1:1 interleaving,
>ie: no sectors skipped; the pc's DMA should be able to handle that; I do
>not know if a modification to DOS's disk drivers is needed.  If there is
>some processing time needed for processing between sectors, this may not
>operate some applications as fast as a slower interleave...
>				zhahai/HiSystems


I welcome the correction, but maintain that anyone putting a harddisk into
their system needs to be aware of the implications of interleave - beyond
the recommendations of the manufacturer.

Thanks again to zhahai for setting me straight, and keeping me honest!


-- 
Tim Margeson (206)253-5240
PO Box 3500  d/s C1-937                          @@   'Who said that?'  
Vancouver, WA. 98668
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