CompuServe Messages

What you're missing is that there is no bus involved when it comes to the PAR unit. The hard disk is connected directly to the PAR hardware. The disk is dedicated to the PAR and has its own format (it's not a DOS disk and it is not connected to any "controller" in your computer). Other than that, everything you said is right. The MAX has a greater throughput but because it uses SCSI instead if IDE. It's got nothing to do with EISA or otherwise. Yes, because SCSI-II disks are a bit faster than IDE, the MAX can use less compression but the difference isn't that much though. At least not nearly proportional to the added cost. You should take a very close look before committing the cash to a MAX system (unless, of course, you have your mind set and don't care). By the way, you can't possibly be getting a steady 10MB/sec out of your SCSI disk. You controller (and your BUS!) cannot sustain that. You're more likely in the 2mb/sec neighborhood at the most. If you want, I can upload a simple test program that will tell you exactly what your transfer rate is. The figures you see in the literatures are only true in "optimum" cases and for very specific amounts of data. Once you start reading a 30 megabyte file, even if all sectors are contiguous, the rate will drop dramatically. The 10mb figure is only true for data already loaded into the controller's memory. That's the absolute maximum rate the controller will pump _that_ block of data to the computer. As soon as the block spans over another DMA read (just 64k), or worse, you have to seek the disk for another sector, you're way down. The 30mb/sec figure (burst mode) is only true for very tiny amounts of data. It can't be even considered in this context. This gets even more complicated if you really care to know the details. Another note worth taking is that there are two sets of "rates". One thing is the rate the controller can sustain between the hard disk and itself. The other rate is between the controller and the computer. In your EISA system, I can guarantee you your hard disk spends a lot of time waiting for the controller to transfer data to the computer. Another note, EISA is doomed. There us no reason whatsoever to keep it alive in a VLB and PCI world. Both are orders of magnitude better, cheaper and by far, more attractive to hardware manufacturers.