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From: info-vax@ucbvax.UUCP
Newsgroups: mod.computers.vax
Subject: Re: physical address space on uVAX-II?
Message-ID: <8601281607.AA08337@mplvax.UUCP>
Date: Tue, 28-Jan-86 11:07:41 EST
Article-I.D.: mplvax.8601281607.AA08337
Posted: Tue Jan 28 11:07:41 1986
Date-Received: Sat, 1-Feb-86 18:18:25 EST
References: <8601271021.AA11074@ucbvax.berkeley.edu>
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Organization: Marine Physical Laboratory, UCSD
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In article <8601271021.AA11074@ucbvax.berkeley.edu> you write:
>
>> The uVAX-II has 8192 map regs to map the entire 4 meg (22 bit) QBUS
>> address space.  Each map reg is a longword (32 bits) and has the generic
>
>What?  If physical memory is limited to 4 meg, why is DEC selling
>8 meg boards for these machines?
>
Physical memory is not attached to the QBUS.  Peripherals are.
So the 22-bit QBUS address space has to be mapped into the potentially
larger memory space for the DMA data transfer.

-- 
	carl lowenstein		marine physical lab	u.c. san diego
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