Time: Sat Sep 20 12:48:31 1997
	by usr04.primenet.com (8.8.5/8.8.5) with SMTP id MAA13191;
	Sat, 20 Sep 1997 12:44:13 -0700 (MST)
Date: Sat, 20 Sep 1997 12:43:57 -0700
To: (Recipient list suppressed)
From: Paul Andrew Mitchell [address in toolbar] (by way of Paul Andrew Mitchell [address in tool bar])
Subject: short hardware tutorial

Reed et al.,

Browse around this website, and keep
looking for the list of disk drives.
At the very end of the "Hard Drive Lots,"
they have a Quantum Bigfoot 6.5GB EIDE,
and a Seagate 9GB Fast SCSI.  It might
be worthwhile to monitor these auctions,
and place a competitive bid just before 
closing.  The current high bidders are
running at <50% of retail prices;  this
means you can buy hard disks for about 
5 cents per megabyte now!  

Read that again!!

As for EIDE drives, don't get into anything
less than the Ultra-DMA drives, which are
running at 33MB/sec transfer rate.  All
older EIDE drives have a 16.6MB/sec transfer
rate -- (not so) obviously inferior for a 
Pentium-class machine with 32-64MB of RAM, 
lots of peripherals, and a clock speed of 
200MHz or more.

Just do the numbers:  the clock speed is a 
rough measure of the bit stream rate in, or
out, of the CPU.  One hundred megaHertz (100Mbits/sec)
at 8 bits per byte is 12.5 MB/sec;  thus,
two hundred megaHertz is 25 MB/sec (+/-).
Clearly, the slower EIDE drives cannot
keep up with the dominant class of Pentiums 
now being shipped.  ASCII is actually a 7-bit code, 
but bit 8 always trails along, because hardware 
channels are built on multiples of two 
(digital/binary arithmetic).  9-track tapes
reserved 8 bits for data, and 1 bit for 
error checking.  

I went with Ultra-DMA 5.1GB EIDE drives from 
Western Digital, because their current cost was
easily 50% less, per megabyte, than a comparable
SCSI-II drive.  For future expansion, and as a
hedge on future changes in these relative 
prices, I also ordered a dual-ported ADAPTEC
SCSI-II controller, which can handle 30 
different peripherals (2 x (16 - 1)).

SCSI-II has a hardware address space for 16 
devices, one of which must be assigned to
the controller itself.  So, each SCSI 
controller can support up to 15 peripherals
(CD-ROM drives, hard disks, scanners, etc.);
a dual-ported SCSI controller can handle
twice this, or 2 x 15 = 30 devices.  Adaptec has
one of THE best dual-ported controllers on the market.

SCSI stands for "Small Computer Systems Interface";
it was a standard developed for large minicomputers,
now scaled downwards in size, due to the onward rush
to still more miniaturization.  It is a very stable
technology, particularly when coupled with fast PCI
motherboards ("Peripheral Component Interconnect").

PCI boards have several "regions", one of which supports
slots for old ISA cards, with a "bridge" chip which 
moves data from these slower cards, onto the faster
native bus.  This PCI architecture was the brainchild
of Intel.  Peter Norton has a great description in one
of his PC bibles, which I have in my book library.

Now, the really good news is here:

The technology to keep your eyes on, is the Alpha chip
from Digital Equipment Corporation.  They are now in
production with a 500MHz chip, which was just upgraded
to a 600MHz model (the top of the line).  They are fast
approaching the gigaHertz threshold, and I believe that
they will be the first to break through (!), despite Intel's
obvious leadership in the mainstream.  So, keep your
eyes on DEC;  I believe theirs will be one of THE dominant
technologies of the near future (e.g. 128-bit internal 
channels).  This is a RISC design, which makes the engineering
a whole lot easier to cycle through multiple generations.
E.g., Hewlett Packard recognized the advantages of RISC many 
years ago.

A commercial-grade GigaHertz (GHz) chip will, quite obviously, 
be a GigaNTic milestone in the history of contemporary computing.

Do the numbers again:  one gigahertz at 8 bits per byte is
5 x 25 = 125MB/sec transfer rate (+/-).  That is, such a
speed could FILL a 100 megabyte hard disk in less than
one second of real time!!  

Pretty exciting, I say!!!


/s/ Paul Mitchell
http://supremelaw.com

copy:  off-site archivists, Digital Equipment Corp.



Dear Clients,

Super deals on surplus computer equipment 
are available at URL:

  http://www.surplusauction.com

There's a real-time auction going on all the time.

Check it out!  It's fun!!

/s/ Paul Mitchell
http://supremelaw.com

      

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