PRINT SERVER IMPLEMENTATION ALTERNATIVES An XCD White Paper
Introduction There is no question that networking capability has become an essential requirement for printers and other output devices. International Data Corporation (IDC) has forecasted that 1.2 million shared networked inkjet printers and 1.8 million shared networked laser printers will be sold annually by the year 2000, but these numbers could be even greater if the cost of networking printers drops to a level low enough so that users can economically network sub-$500 printers. There are three ways to implement networking capabilities in a printer. Intelligent print server card. In this approach, a plug-in card with its own processor and provides the networking function. The Hewlett-Packard JetDirect is the most famous example of an intelligent print server card. On-board ASIC print server chip. An ASIC (Application Specific Integrated Circuit) is a custom chip that combines multiple functions in a single package. Some manufacturers have recently introduced ASICs designed specifically for print server applications. These ASICs typically provide a processor, network interface, parallel and serial I/O, plus miscellaneous logic. In this approach, the OEM puts the ASIC on his printer controller, thereby eliminating the need for a separate plug-in card. Software-only print server. Because printer controllers typically use powerful RISC processors, there are often spare cycles available. Since the print server function is largely input/output intensive, it is quite possible that the processor on the printer controller can also handle this function without significantly degrading the performance of the printer. The print server function in this case operates as task running on the printer controller s multitasking operating system. The three methods are discussed in more detail in the following sections. Intelligent Print Server Cards The intelligent print server card has traditionally been the most popular method of implementing networking capabilities on a printer (see figure 1). The reason for this is partly historical. In the early days of network printing, the printer controllers used relatively low-performance CISC processors that were simply not capable of handling both the printing and networking functions. In addition, the networking function added considerable cost to the printer. Therefore, it was necessary to offload the networking into a separate extra-cost intelligent card. Even today, however, intelligent print server cards remain very popular. Some of the reasons for this popularity include: Modularity. The user can simply plug in a card that meets his exact requirements. For example, Hewlett-Packard offers 10baseT, 10baseT/10base2, 100baseTX/10baseT, and Token Ring cards for its line of LaserJet printers. In addition, there is also a large selection 2
of third-party cards available, such as XCD s XJet line of DEC and Banyan VINES compatible cards. This kind of flexibility allows HP to address virtually any network printing application. Performance. Because the intelligent print server card has its own processor and, the networking function does not affect the performance of the printer controller s processor. As a result, both the networking and printing functions can operate faster. Cost considerations. Because the printer market is highly competitive, it is not feasible to burden low-end and mid-range printers with the extra cost of networking hardware. By making the print server an add-in option, only those customers who need networking will pay for the networking capability. Obsolescence. Newer networking capabilities like 100baseTX are continually emerging. With an intelligent print server card approach, the user can upgrade to these new technologies without having to replace his printer. The drawback of an intelligent print server card is cost. The card itself is expensive due to its separate processor,, supporting logic, printed circuit board, and mounting hardware. In addition, the printer must bear the additional costs of interface logic and mounting hardware to handle the card. Typical intelligent print server cards in 1998 cost in the $120 to $150 range (this price generally includes the networking software license). Printer Controller interface logic interface logic network Intelligent Print Server Card Figure 1 Intelligent Print Server Card 3
A relatively recent trend in intelligent print servers is the PCI bus. The PCI bus has been widely implemented on personal computers, and as a result, the component costs required to implement this bus are rapidly dropping. Since the PCI bus also provides exceptionally high bandwidth, it is the ideal bus for new printer controller applications. Both Hewlett-Packard and Lexmark have implemented the PCI bus on their latest generations of printers. The advantages of the PCI bus are discussed in greater detail in the XCD White Paper, PCI Bus Advantages for Network Printing. On-board ASIC Some print server-specific ASICs have begun to appear on the market during the past year. These ASICs typically provide a RISC processor (usually the ARM RISC processor) with a network interface, some serial and parallel ports, DMA, bus, and controllers, and other logic. The OEM must typically provide his own plus physical interface circuitry (the ASIC usually provides a general parallel port, so the OEM must adapt this port to connect to the internal bus of the printer). The total cost of such a solution is $50 to $60 or more in 1998, including the cost of the ASIC,, flash, interface circuitry, LAN physical layer chip, and other logic. This cost does not include the networking software license. Printer interface logic interface logic* ASIC (+ MAC) network PHY *The ASIC typically provides a general parallel interface, but additional logic is usually required to interface to the printer controller Figure 2 On-board ASIC 4
The idea behind an on-board ASIC is that the OEM can incorporate the chip directly on the printer controller, thereby eliminating the cost of a separate plug-in intelligent print server card (see figure 2). This approach eliminates the cost of the extra printed circuit board and mounting hardware, and can also simplify the interface circuitry. The other advantages of an ASIC include: Reduced size compared to discrete implementations. A single chip replaces many chips, which can be an important factor for small printers. Simpler design. The OEM can incorporate most of the print server function with a single chip, which reduces the design effort compared to a discrete chip implementation. Lower initial cost compared to using off-the-shelf chips. At least during the first few years, an ASIC will typically be lower in cost than using off-the-shelf components. High performance. As with the intelligent print server card approach, the print server function operates independently of the printer controller, thereby increasing overall performance. The ASIC approach, however, does have some drawbacks: Not modular. Most of the ASIC solutions only support Ethernet and Fast Ethernet (one company does provide both Token Ring and Ethernet). This means that adding other network types can require a fair amount of additional hardware and software. More expensive than a software-only solution. Even though the cost of ASIC solutions is dropping, there is still a significant additional cost compared to a software-only solution. Potentially higher costs in later years. Although ASICs are initially lower in cost than offthe-shelf solutions, this advantage typically goes away in later years. That is because large processor chip manufacturers like Motorola, AMD, and Intel are continually introducing products with increasing amounts of integration and lower costs. In addition, discrete components like networking chips are also rapidly declining in price. For example, one ASIC that was introduced in 1997 at a price of $35 fell to $28 in 1998. During this same period, the price of the equivalent standard components fell from $45 to $29. Single source. The print server ASICs are typically manufactured by relatively small companies, which may cause manufacturing supply problems in the future. Software-only Print Server The latest trend in network printing is to use the printer controller processor to handle both the printing and networking functions (see figure 3). This software-only print server approach is now possible because printer controllers use very high performance RISC processors with sophisticated multitasking real-time operating systems like Wind River System s VxWorks. The advantage, of course, is that cost of adding networking capability is greatly reduced because of the elimination of the separate print server processor,, and supporting logic. This means that the 100baseTX/10baseT networking function can be added for the cost of the Media Access Controller (MAC) and physical layer chips (PHY), or about $15 and $10 respectively in 1998 costs (although it could be argued that an allocation of costs should be factored in, this cost is pretty negligible given the large amounts of available in most printers). Note 5
that some RISC processors now have built-in MACs, so the cost of implementing networking on these processors is just the price of the PHY. The cost of the networking software license is additional. In addition, off-the-shelf 100baseTX chip pricing is likely to fall significantly over the next few years, if the rapid drop in Ethernet chip pricing over the past ten years is an indicator. This drop in price will almost certainly exceed the drop in price of a proprietary ASIC solution because of the much higher volumes. Also, note that an Ethernet-only solution will be much lower in cost than a 100baseTX/10baseT solution. Therefore, if 100baseTX is not needed, the price differential compared to most ASICs is substantially greater, since the ASIC must bear the cost of the more expensive 100baseTX/10baseT MAC even if 100baseTX is not used. Printer network MAC* PHY *Not required if has built-in MAC Figure 3 Software-only Print Server The networking function can either be built onto the printer controller board, or it can be a nonintelligent plug-in card. As discussed previously, the PCI bus has emerged as the best bus for new printer controller designs because of its low cost and high performance. PCI is particularly ideal for non-intelligent cards because such cards require a minimum amount of interface logic and are therefore very low in cost (intelligent PCI cards require a significant amount of logic to connect the card s processor local bus to PCI). In addition, there are a number of off-the-shelf non-intelligent PCI card designs for Ethernet, Fast Ethernet, Token Ring, and other networks, so development time is minimized. The only change required to the software-only print server is a new network driver. 6
The advantages of a software-only solution include: Lower cost. There is no separate processor,, or interface logic required. Simpler hardware design. Modularity. By using non-intelligent plug-in network cards, the OEM can meet the networking requirements of virtually any customer (for example, Token Ring, Fast Ethernet, etc.). An example of a software-only print server is XCD s Soft Print Server Print Protocol Library, which is shown in Figure 4. Soft Print Server is a relocatable image that is linked with the Wind River VxWorks operating system kernel, or with an application, to provide network printing support for a wide range of protocols. It includes a set of protocol stacks that augment the IP stack provided by VxWorks, including NetWare, AppleTalk, DLC/LLC, NetBEUI, VINES, LAT, and Direct Mode IP/IPX. It also provides printing and management services, such as LPD, Internet printing, NetBIOS over IP, SNMP, http, and much more. The printer controller function can interface with the XCD printing and management services, or it can communicate directly with the built-in TCP/IP stack. Additional information on Soft Print Server can be found on the XCD web site (http://www.xcd.com) or by contacting XCD. Printer Controller Application Printing: LPD, NDS, PCPrint, etc. Management: SNMP, http, TELNET, etc. VxWorks Kernel with TCP/IP Non-IP Protocols: IPX/SPX, DLC/LLC, NetBEUI, AppleTalk, VINES, LAT, Windows Peer-to-Peer Printer VxWorks SENS MUX Ethernet Network Driver Figure 4 XCD Soft Print Server VxWorks Print Protocol Library The only potential drawback of the software-only print server approach is performance. Since the processor on the printer controller handles both the printing and networking functions, it can have a greater burden than it would with just the printing function. The actual transfer rate depends on at least three factors: 7
Processor speed and bus bandwidth. A 66MHz CISC processor with a 16-bit bus will obviously be much more burdened by a software print server than a 600MHz RISC processor with a 64-bit PCI bus. Nature of print job. PostScript jobs are interpreted, and therefore require much more processing time than PCL jobs. As a result, the performance of the print server function may be degraded in a PostScript-intensive environment. Efficiency of printer controller software. An efficient printer controller software implementation will provide more free cycles for the print server function. About XCD XCD Incorporated is a leading supplier of network printing and Internet imaging solutions. The company is widely known as a technology leader with innovations such as the industry's first 100baseTX external print server, the first PCI compatible print server, and the first print server with Internet remote printing capabilities. XCD is the only print server company that is an authorized development partner with both Hewlett-Packard and Lexmark. Because of its technology leadership and commercial success, XCD was honored as a member of Computerworld Magazine's list of Hot Technology Companies. For more information, contact us at (949) 399-0820, fax: (949) 399-0825, e-mail: sales@xcd.com; or check out our web site at http://www.xcd.com. 8