Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!apple!casseres
From: casseres@Apple.COM (David Casseres)
Newsgroups: comp.sys.next
Subject: Re: How did they make the printer so cheap?
Message-ID: <143@internal.Apple.COM>
Date: 25 Oct 88 18:41:16 GMT
References: <0XKoeky00UgXM3T24=@andrew.cmu.edu> <73489@sun.uucp>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 23

In article <73489@sun.uucp> swilson@sun.UUCP (Scott Wilson) writes:

>I don't know squat about printers, so I'm confused about something.  If
>the computer is going to build the image then for an 8 1/2 x 11" sheet
>at 400 dpi wouldn't you need 8.5x400x11x400 bits of memory in which
>the image is built?  This works out to be roughly 1.8 meg of memory
>(assuming I didn't screw up somewhere).  Does this mean that to
>compose a page for the printer the NeXT machine has to briefly use
>this much of its memory?  What kind of transfer rates are expected
>out the printer port?

You didn't screw up, it is roughly 1.8 meg.  I presume that they do indeed
pig up this much RAM in order to print.  Remember they have a virtual
memory system as well as lots of RAM, so they can do this; at worst, it
might mean that applications would have to do more swapping while printing
is in progress.  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, once
the paper has begun to roll.

David Casseres