Path: utzoo!attcan!uunet!husc6!bloom-beacon!apple!phil
From: phil@Apple.COM (Phil Ronzone)
Newsgroups: comp.unix.aux
Subject: Re: Some questions about A/UX
Message-ID: <21057@apple.Apple.COM>
Date: 22 Nov 88 17:54:58 GMT
References: <941@ccnysci.UUCP> <19528@apple.Apple.COM> <964@ccnysci.UUCP> <19816@apple.Apple.COM> <1011@ccnysci.UUCP>
Organization: Apple Computer A/UX Group
Lines: 34

In article <1011@ccnysci.UUCP> alexis@ccnysci.UUCP (Alexis Rosen) writes:
>.... Writing to a buffered SCSI disk can go up to 400K/s. That's great...
>but not too great. The Wrens can sustain a throughput of 1MB/s. That's really
>great. So why is the Mac's "great" != the Wren's "great"?
>
>In other words, if the lack of DMA isn't slowing down the Mac, what is???
>It is clearly not going as fast as it should.

One last last shot -- then I'm forgetting the matter. Typical UNIX SV
filesystem, 50 reads a second, each read to essentially a random block.
Assuming fast disks with 16MS average seek times. Each read/write
takes maybe 200 to 900 microseconds, depending on hardware. This gives
us a time to ACQUIRE IN MEMORY, for each block, 16MS + ~500 microseconds.

Now if we had an INFINITELY FAST DMA/tranfers mechanism, we could cut
that figure down to 16MS + ~0 microseconds. Notice the blazing increase
in throughput!!! :-)

OPEN QUESTION - why do you think the "Mac is not going as fast as it should"?
If this is on a comparsion basis, tell me the equivalent machine that runs
faster. Equivalent means 68020, ~16MHz, memory management, SCSI disk I/O,
SVR2, etc. We really do want to know of equivalent hardware that runs better
because of software. When we find it, we want to make ours run faster too.

WARNING -- "fast & faster" can be exceptionally subjective.
+------------------------+-----------------------+----------------------------+
| Philip K. Ronzone      | A/UX System Architect | APPLELINK: RONZONE1        |
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