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From: casseres@Apple.COM (David Casseres)
Newsgroups: comp.sys.next,comp.arch
Subject: Re: How did they make the printer so cheap?
Message-ID: <172@internal.Apple.COM>
Date: 31 Oct 88 22:57:26 GMT
References: <0XKoeky00UgXM3T24=@andrew.cmu.edu> <73489@sun.uucp> <143@internal.Apple.COM> <5784@hoptoad.uucp>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 32

In article <5784@hoptoad.uucp> gnu@hoptoad.uucp (John Gilmore) writes:
>casseres@Apple.COM (David Casseres) wrote:
>>                  At best, the 1.8 meg would be "free" in the 8 meg total
>> system, and since the I/O to the printer from RAM is DMA, the applications
>> would be totally unaffected.  Nice.  I don't recall the transfer rate (it's
>> in the Byte article) but it's about what you'd need to hose that 1.8 meg
>> out to the printer within the 6 seconds or so that the printer allows...
>
>I'm not sure what he means by "free" but the RAM is certainly there to
>be "used"; that's what RAM is for.

I just meant that in the best case, the space could be allocated without
having to swap anything else out.

>...  However, just having DMA between
>memory and the printer does not guarantee that "applications would be
>totally unaffected".

Correct; I should have said virtually unaffected, and I should have added
"by the I/O requirements."

>But don't forget the CPU time burned by the PostScript interpreter.
>We sell one, we know; high quality imaging of 1.8MB of bits in an
>interpreted language definitely runs the CPU at peak for a while.

I don't think this will have a very large impact on applications running
on the same machine.  We know their implementation of Display PostScript
can paint the NeXT screen fast enough for a whizzy interface, and that
screen is a million pixels X 2 bits/pixel = 2 megabits or about 0.25 MB.
To draw a page of about 2 MB would take about 8 screen times, which just
doesn't sound to me like a big hit.

David Casseres