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Notes About PC-NFS Memory Usage

Sun Microsystems offers a software package called PC-NFS that provides network services from a personal computer to a remote computer over an ethernet. To explain further, PC-NFS allows a user on a PC to log in with TELNET and transfer files with FTP. The NFS part of the package uses Sun's Network File System to mount a directory on a Sun file server as a pseudo disk drive on the PC, such as `g:'. Standard DOS commands are used on the PC to access files stored on the NFS-mounted directory, and UNIX commands are used to access the same files from the UNIX side. Also, up to 3 UNIX printers can be accessed by the PC via PC-NFS. For example, the Agricultural Engineering department and the Soil Erosion Lab have been using PC-NFS for a few years. Currently, there are 23 personal computers running PC-NFS which access the Sun file servers, STABLE and PASTURE. This software package is very convenient and useful, but it is not without its problems.

A problem encountered while running PC-NFS on a PC is the lack of available conventional memory to run some large application programs, such as AUTOCAD. The three drivers for PC-NFS require about 85 Kbytes of memory on the PC, which by default is loaded in the 640 Kbytes conventional memory area. This creates a problem; some PC applications expect to use nearly all the 640 Kbytes conventional memory and will not run if other memory resident software is using the space.

One solution to the memory problem is simply to use at least two sets of CONFIG.SYS and AUTOEXEC.BAT files. One set installs PC- NFS when the user wants to use the network, and the other installs the large application, but not the network. However this solution has an inherent disadvantage. It makes the network unavailable to the user while running the large application program. Therefore, the user cannot store or access DOS files stored on the file server nor access the network printers.

A better solution is to use a PC memory management program to load the PC-NFS.SYS driver into the high memory area between the 640 Kbytes to 1.0 Mbyte address. This allows the network to run along with a large application program while using only one CONFIG.SYS and AUTOEXEC.BAT file set. Unfortunately the largest driver, PC-NFS.SYS, has a size of 65 Kbytes; while the default contiguous space in high memory is 64 Kbytes! To remedy this situation, I have used Quarterdeck's QEMM386 program to move things around in high memory and to provide an 88 Kbytes contiguous area to load PC-NFS.SYS. Since some applications will use parts of the high memory area, which does not leave a large enough block of high memory for PC-NFS.SYS driver. This requires the user to customize the QEMM arguments in the CONFIG.SYS file whenever a new application is loaded. This solution can be tedious.

So, the best solution is to install MicroSoft's DOS version 5.0 on 286 or better systems. DOS 5.0 has several advantages over earlier versions of DOS. One big advantage is that DOS 5.0 moves the DOS kernel out of conventional memory and above the high memory area. This frees up space for network drivers and large application programs to reside together in conventional memory.

At Agricultural Engineering, we have DOS 5.0 installed on three of our four Mbytes 386 machines and can successfully run the network drivers along with several of the large application programs. >From our experience we have found that the DOS 5.0 commands, DEVICEHIGH and LOADHIGH, are useful to load drivers into high memory. Also, we have found at least one application that uses its own expanded memory manager and is incompatible with the DOS 5.0: EMM386.SYS expanded memory manager command.

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