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Path: utzoo!linus!philabs!cmcl2!rna!dan
From: dan@rna.UUCP
Newsgroups: net.periphs
Subject: Qbus peripherals questions...
Message-ID: <194@rna.UUCP>
Date: Wed, 11-Jan-84 20:37:47 EST
Article-I.D.: rna.194
Posted: Wed Jan 11 20:37:47 1984
Date-Received: Fri, 13-Jan-84 04:56:35 EST
Lines: 24

Hello folks,

	1) Does anyone have any experience with the USDC CSS-800
		disk/tape subsystem on either the Qbus or the
		Unibus ?

		This drive has an internal cache which speeds reads.
	It also does read-aheads (probably not very useful for UNIX).

	2) Any comments on the newer Qbus block DMA protocol as it
		relates to currently available disk and tape
		controllers ?
		I don't know of any disk controllers other than the
	DEC RD50 which can make use of the block DMA protocol.
	However it seems that all new DEC (and 68000-based) CPU's will
	be using block DMA to get higher Qbus bandwidths. In particular,
	some 68000's and the MicroVAX I will (I believe), use block DMA
	to load their caches. It just seems that if you buy a Qbus disk
	controller today, you will lose Qbus bandwidth which may be
	important with these newer CPU's. I guess you can't have everything.

					Cheers,
					Dan Ts'o
					...cmcl2!rna!dan