Re: pci-to-parallel vs usb-to-parallel?

Tzafrir Cohen wrote:
On Mon, Aug 18, 2008 at 09:00:06AM -0700, Bob McGowan wrote:
Tzafrir Cohen wrote:
On Fri, Aug 15, 2008 at 10:33:50AM -0700, Bob McGowan wrote:
Mike Fontenot wrote:
My new PC doesn't have a parallel port on the back (or anywhere else),
and I need one for my HP1200 B/W laser printer. I've seen inexpensive
PCI cards that have one or two parallel ports, and also some cables that
convert between USB and parallel.
--<Deleted on purpose>--

Speed over USB will be limited to the PP port speed at max but could be impacted by other devices on the USB bus, if there are any.
Speed? Even USB1.1 is about the same speed of a parallel port (probably
faster). And with USB2 you have nothing to worry about with the speed.

At first reading, I thought you misunderstood my point. On second reading, I think maybe I misunderstand yours. So, to see if I grok what you said...

Since USB 2 can deliver data much faster than the parallel device can consume it, even if you have multiple devices on a single USB bus, data will probably get to the printer fast enough for it to receive data at its highest design rate.

But, for USB less than 2.0, assuming the USB speed is about equal to the parallel bus speed, multiple devices could impact data flow enough to cause the printer to have to wait on occasion.

According to Wikipedia's IEEE 1284 spec. parallel port speed for EPP/ECP is 2/2.5 MBits/s, while USB 1.x is 1.5/12 MBits.

So, unless the USB is constrained for some reason to the 1.5 MBits/s low speed, USB data rates should be high enough to keep the printer data transfer rate at it maximum.

Am I close to understanding correctly?

So you don't have a USB 2.0 port on your system?

The "you" in my statement is a generic one, implying only that "if" someone had such a system, that system would potentially have issues with data transfer speeds.

This in no way implies that I or anyone I know or know of, has such a system.


There's also the strange option of buying a PCI card of a USB
controller. Those are quite common and cheap, but then you lose the edge
mentioned in:

If it were me, I'd factor in the cost, as well. If they were close, I'd probably choose the USB interface path, mostly due to not needing to open the chassis to implement it.


--
Bob McGowan
Symantec, Inc.

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