Printer memory? How does it work? HELP pls.

OK, the following only applies to laser printers. Ink-jets, dot-matrix <i>et-al</i> get data fed line by line from the host computer, so memory isn't particularly relevant.

Laser printers need to hold an entire image of each page in memory before printing. This is because once it feeds in a sheet, it is committed to sending that paper through at a set speed (if it stopped to wait for data, the temperature of the fuser unit would burn the page). Your 78mb brochure would be fine, because only the size of each page is relevant.

I've seen a laser with 4mb run out of memory and refuse to print a page consisting of a single, hi-res image. A unit with 32mb should be fine :smile:

Beyond this, printers extensively process data fed from the host machine. The more memory it has, the more pages can be held locally, the sooner the host PC is released...

Thanks for the explanation. I appreciate it very much. I didn't get this part though

"Your 78mb brochure would be fine, because only the size of each page is relevant."

If I had 32MB on my laser printer then a 78MB file wouldn't fit right? Only thing it can do is feed data in 2 or 3 parts, feeding the next part of the data as soon as memory on the printer becomes free. Am I right?

I have printed 70+ MB PSD files countless times on our HP 4500 color laser printer with 32MB memory.

As long as <i>each page</i> of the brochure is less than 32mb, it's cool.

It is more complicated than that though. Basically a printer will process data and hold a resulting 'image' in memory which can be fed directly to the laser. The size of this image will bear little relation to the size of the original file.

I realise this explanation isn't of much practical use! All I can say is, 32mb is plenty, but for any unit with a heavy workgroup workload, the more memory the better :smile:

The thing is there's only 1 page and it's 78MB.

In which case the printer is receiving data, processing and building a resulting image which is less than 32mb. Whatever, that entire page <i>is</i> held in the printers memory before the sheet is fed in.

Photoshop files are huge, they contain all sorts of elements that are separated so they can be edited individually. As I said, the processed data, ready to be sent to the actual laser itself (that is, the laser head), will bear little relation to the original file size. Have to admit though, I'm no expert when it comes to Photoshop and the like, my knowledge comes from experience in the hardware field. Specifically, as an engineer at Oki and Lexmark.

For the final image:

8.5" x 11" sheet = 8" x 10.5" printable area (typical)

8" x 300dpi = 2400 dots width
10.5" x 300dpi = 3150 dots length

2400 dots x 3150 dots = 7,560,000 dots

With one print colour (black) each dot can be represented with one bit.
7,560,000 bits = 945,000 bytes ~~ 945 kilobytes ~~ 1mb.

Colour gets a little more complicated, but essentialy it had to form 4 images in memory, one for each of the black, cyan, magenta, and yellow toner cartridges. This takes four times as much memory, so you're looking at about 4mb total for a 300x300dpi 8" x 10.5" image.

For 600dpi you have to quadruple the ammont of memory needed (x2 in two dimensions = x4).

Of course, the memory has to hold not only the final image but also the information on how to "construct" the final image (ie: the data sent from the computer in postscript or PCL5 or HP/GL2 or whatever language your printer speaks). You can see how much space this information takes up by looking at the size of your print job in your printer control panel.

Most printers now use data compression as well which helps conserve memory.

The comment made about inkjet printers is true for most inkjets out there, which can be classified as "dumb" and do not have their own print processors. There are, however, also "smart" inkjets which speak languages and contain processors and substantial amounts of memory.

- JW<P ID="edit"><FONT SIZE=-1><EM>Edited by JCLW on 07/12/02 02:32 PM.</EM></FONT></P>