Path: utzoo!utgpu!water!watmath!clyde!rutgers!iuvax!viking
From: viking@iuvax.UUCP (Jon W. Backstrom)
Newsgroups: comp.sys.mac
Subject: Will DMA ever be used in the Mac?
Keywords: hardware, mac
Message-ID: <5094@iuvax.UUCP>
Date: 11 Dec 87 00:45:43 GMT
Organization: Indiana University, Bloomington, IN
Lines: 48

I can't help thinking what a wonderful machine my Mac II is but how much better
it could be if Apple would stop insisting on doing *everything* in software.

For the cost of a few DMA chips (what? $0.35 each?) the NuBus could be made to
operate in burst mode (like it should), the 68020 could spend more time working
and less time pulling bytes of the hard disk, and who knows what else.

All this seems to harken back to the days of the Apple II and the clever ways
Woz was able to reduce the chip count by using software drivers...(Hey! Let's
*write* a disk controller!).

That was fine for a machine at that time and the early market appreciated the
reduced costs associated with such techniques.  The Mac II is probably going to
suffer in the workstation market (next to 80386, Apollos, and Suns) unless it
can operate faster, however.  As a single user machine, I guess none of this
really matters much, but two things seem to need addressing:

1) DMA disk access seems to be a needed feature.  Does A/UX slow down when it
   has to swap memory with 5 users, for instance?  With the CPU being tied up
   all the time, speed is bound to suffer.

2) Screen I/O is also managed by the CPU.  I dream of the day that Apple or
   someone (RasterOps?) develops a video card with a graphics co-processor.
   This is made more difficult by the need to run the quickdraw routines, but
   maybe somebody can do it!  (Apple, are you listening?)

Perhaps the use of the NuBus will allow someone to offer a videocard with
both a graphics co-processor and a DMA SCSI port....naw, I'm reaching here, I
know.  But the idea is a good one.

I'm definitely not a hardware type, but I really want to see Apple go places.
My Mac II is great but I'm hoping to see some of these things develop in the
coming year....and maybe Apple will 'do it right' on the 68030 machine for '89.

Responses welcome...does anyone have multiuser A/UX experience vs 80386 XENIX?
Does the lack of a DMA disk controller really matter?  

-------------------------------------------------------------------------------
|  Jon W. Backstrom             "Yah sure...we gonna have fun, you bet!"      |
|  Computer Science Department                                                |
|  Indiana University           UUCP: {ihnp4,pyramid,rutgers}!iuvax!viking    |
|  Lindley Hall 101             ARPA: viking@iuvax.cs.indiana.edu             |
|  Bloomington, IN  47405                                                     |
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|  (812) 335-2849 (Office)       complex devices of great reliability; and    |
|  (812) 336-3660 (Home)         something is bound to come of it."           |
|                                                 - Vannevar Bush (1945)      |
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