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From: dag@chinet.UUCP
Newsgroups: comp.sys.atari.st
Subject: Re: Daisy chaining SH204's
Message-ID: <1883@chinet.UUCP>
Date: Sat, 21-Nov-87 11:05:35 EST
Article-I.D.: chinet.1883
Posted: Sat Nov 21 11:05:35 1987
Date-Received: Mon, 23-Nov-87 00:35:28 EST
References: <8711171046.AA09562@ucbvax.Berkeley.EDU> <317@mks.UUCP> <570@aucs.UUCP> <5990@jade.BERKELEY.EDU>
Reply-To: dag@chinet.UUCP (Daniel A. Glasser)
Organization: Chinet - Public Access Unix
Lines: 62
Keywords: SH204
Summary: DMA port not limited to two devices

In article <5990@jade.BERKELEY.EDU> c60a-2ae@web4e.berkeley.edu.BERKELEY.EDU (John Kawakami -O^O-) writes:
>In article <570@aucs.UUCP> 870646c@aucs.UUCP (barry comer) writes:
>>I have a general question for all of the hackers out there, "Can you 
>>chain together the SH204 drives by installing an extra DMA socket on
>>the back of the case, providing that you wire it pin to pin with the
>>present socket?".  [some stuff deleted]
>>later
>>Barry
[John KaWaKaMi's initial comments deleted...]
>But back to the question.  I think it's limited to two.  I recall
>something about the drive port pins: a drive select pin to address
>drive one and another for drive two.  The drive ports are just that,
>drive ports, not serial ports that "converse" with the devices.
>
>HEY everybody, correct me if I'm wrong (hope I am.).
>
>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>| JoHn KaWaKaMi alias spectacle -O^O- alias c60a-2ae@widow.berkley.edu      |
>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


Okay, I'm not everybody, but I will take a stab at it.

			**********************
			*** You are wrong. ***
			**********************

The floppy connection is limited to two drives, and though the data comes
in through the DMA chip from the floppy, this is not the DMA port.  The
DMA port allows connection of a fairly large number of devices (8 or 16?)

I've spoken in the past with some people at Atari about connecting
a second DMA device, and they said that the extender would have to
be buffered since the DMA chip cannot handle much more load than the
SH204 puts on it.  I believe that several vendors now sell drives/controllers
which have DMA daisy chain plug.

Include in this number ICD, from Rockford, IL.  Maybe Supra now sells one,
and I believe that even Atari has shown a drive with this feature.

You can, however, add a second drive to the controller inside the SH204.
I don't have details right here.

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-- 
					Daniel A. Glasser
----------------------------------------+----------------------------
Cheese is not a discipline!		| ...!ihnp4!chinet!dag
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