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Accepts Input From Up To Three Computers Simultaneously |
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Buffers Output To One Or Two Peripherals Sequentially |
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For Hewlett-Packard HP-IB Desktop Computer Installations Incorporating Plotter And/Or Printer Peripherals |
Three Independent Input Ports Plus Microprocessor Intelligence
The Cloverleaf has three independent input ports, allowing all three computers to input data simultaneously, which quickly frees the computers for additional work. But the Cloverleaf does far more than simple multiplexers. It buffers, queues and sequentially outputs each job to two output peripherals, such as a printer and plotter - in chronological order.
Maximizes Utilization Of Expensive Peripherals
The Cloverleaf gives all three users access to both output peripherals. Allows everyone access to "the good plotter" without swapping cables.
Available With Up To Two Megabytes of RAM
Standard Cloverleaf configurations include 256K Bytes or one megabyte of RAM. An optional second megabyte of memory can easily be added to the one megabyte version. The Cloverleaf's large memory capacity is especially desirable because it is being fed input data from three different computers. The memory is efficiently apportioned among the three inputs according to need - with no artificial or arbitrary memory-wasting divisions.
Flexible User Controls
Front panel push buttons allow the user to pause or abort the current job, and to poll the plotter for program-required setup info without losing queue data or powering down. Internal switches provide for a wide variety of options to accommodate various peripherals, such as enabling automatic printer formfeed.
Compatible With a Wide Variety of Hardware/Software The Cloverleaf employs standard IEEE-488 interface, cables and connectors. Existing cables can be easily transferred. the unit is designed to be transparent to software. In most cases, absolutely no software changes need be made. Cloverelaf intelligence can interrogate the plotter and send setup info back to the relevant computer program when required.
In most cases, Cloverleaf productivity increases will be similar to, or (see next page for explanation) just a little lower than those realized with the Eventide Expressway. We can confirm Cloverleaf compatibility and performance with a wide variety of hardware/software configurations.
At first glance, the Eventide Expressway and Cloverleaf appear quite similar. Here we explain the similarities - and key differences between the two, so that you can determine which of Eventide's productivity boosters will best suit your needs.
Thumbnail Description - The EXPRESWAY is designed for use with a single computer and one or two peripherals. It accepts data from the computer at high speed, and parcels it out to the two peripherals (typically printer and plotter) simultaneously. Thus, the computer is freed very rapidly for additional work, and both peripherals are used to the absolute maximum advantage.
The CLOVERLEAF is designed for use with up to three computers and one or two peripherals. It also accepts data from the computers at high speed (albeit somewhat slower than the Expresway), and parcels it out to the two peripherals (again, typically printer and plotter) sequentially. Thus , all the computers are freed very rapidly, and greater peripheral utilization is frequently accomplished.
Similarities - The majority of the hardware in both units is identical. The Cloverleaf, however, has a significantly more complex front panel, and an additional I/O port board.
Both units are set-up as "peripheral emulators." In normal operation, a computer (or computers) connected to the input ports cannot discern that they are not communicating with the peripheral itself. This transparency allows both units with a wide variety of software packages, including those that use HPGL plotter interrogation sequences. The Expressway and Cloverleaf both interrogate any connected plotters during their turn-on sequences, and store a list of plotter-dependent information which cna be made available to the computer on request.
Both units can be ordered with 256K, 1 meg or 2 megabytes of memory. (But please note that Eventide recommends at least 1 meg of memory for Clovereafs.)
Comparisons and Differences: Input Considerations - The Cloverleaf can accept inputs form up to three computers, as compared with the Expressway's single input. Therefore, the Cloverleaf's software must be somewhat more complicated, to be able to deal with multiple job queues, addresses, etc. Thus, the maximum input data rate of the Clovereleaf is specified as 10KBytes/second. At first blush, it might appear that the Expressway will operate twice as fast. In practive, however, this is usually not the case.
Most printing and plotting operations are significantly slower than either of these rates, and are the limits to the speed at which the complete system operates. Consider a typical scenario...you want to LIST a BASIC program. The computer typically does three things during a list: It reverse compiles the internal code representation, it sends this to an I/O buffer area, and then transfers the buffer area to the peripheral. Assume for the sake of simplicity that each of these operations requires an identical time period, and that the I/O operation would normally (as with the Expressway) proceed at 20KBytes/second. Total listing time in our arbitrarily equal units is 1 + 1 + 1. Now assume that the I/O operation is half as fast (as with the Cloverleaf). Total listing time is now 1 + 1 + 2. Thus, even though the Cloverleaf is half as fast, total thruput is degraded by a factory of only 4/3.
In practice, benchmarks obtained with the Cloverleaf are usually almost as good as those of the Expressway, when the two units are used under the same circumstances. The only times that they become significantly worse (up to a factor of 2) are in cases where the original improvement is exceptionally good to begin with. It is true that speed is further degraded when using the Cloverleaf with multiple simultaneous inputs. However, even in the worst case, input rate is typically 10-20 times faster than the typical printer, and of course, even better when compared with plotter speeds. And it is unlikely that all three inputs will be sending data exactly simultaneously. Even in cases in which files appear to be sent thusly, data tends to come in bursts.
Output Considerations - The key difference is that with the Expressway, BOTH PERIPHERALS OPERATE SIMULTANEOUSLY. Each is connected to a separate port with a separate cable, and Expressway software will send data to each peripheral as fast as it can be accepted. With the Cloverleaf, the two output peripherals, operate SEQUENTIALLY, operating from the same output port. For applications in which both peripherals are used extensively, the Expressway is clearly more desirable (assuming that its single input in no a serious limitation). In cases where one peripheral is used heavily and the other lightly, this difference is likely not to matter too much. Note too, that the Expressway offers optional output modules available for controlling RS232 peripherals. The Cloverleaf can only access HP-IB.
Memory Considerations - Naturally, productivity enhancements available with either unit are predicated on there being sufficient memory storage available. If either an Expressway or a Cloverelaf should completely fill up during operation, the I/O rate will drop to the rate at which the peripheral can accept data. Ample memory capacity is especially critical to the Cloverleaf because its memory will be called upon to buffer data from up to three computers. We strongly recommend purchasing the Cloverleaf with at least one megabyte.
Control Considerations - The Cloverleaf is a bit more complicated to control since it can interact with multiple computers and users. It has a different set of front panel LED's and also has several push button controls. The controls allow you to pause or abort the current job. Another switch allows re-inquiry of the plotter without powering down or losing queue data. Internal switches select various options for each computer and for each peripheral. They allow automatic printer formfeed and plotter pagefeed on selectable timout, or on a selected ASCII character. Printer/plotter selection is similar to the Expressway.
Compatibility - The Expressway and the Cloverleaf are compatible in that the input of one may be connected to the output of the other and each unit will function as specified. Both units may also be connected in series with themselves for additional memory or functionality.
To Summarize, Choose the Expressway - when you have a single computer to connect to two expensive and/or slow periphals and optimum performance productivity gains are desired.
Choose The Cloverleaf - when you wish to share one or more peripherals among more than one computer, and one peripheral is used lightly, or if your major objective is to save people and computer time, and maximum usage of both peripherals simultaneously is less important.
Choose Both - when you want to obtain maximum usage from more than one computer AND both peripherals simultaneously. Connect the Expressway input to the Cloverleaf output.
