Footnotes on Educational Technology Center micros

ISA (Industry Standard Architecture) is the more formal name of the bus used on the PC and XT machines (8 bits wide), and AT's and PS/2 models below the PS/2 model 50 (16 bits wide).

Although our PS/2 model 70 holds a full 2 megabytes (upgraded to 6 MB early in 1994), 64K are reserved for the double-sized BIOS (which the model 80 also has, but whose resulting memory loss it doesn't report) Less than the full 6 megabytes is therefore available on the model 70.

The 8086 has a 1-megabyte address space, which prevents the Olivetti's from using even expanded memory.

The Olivetti hard discs have separate DOS and p-System partitions, essentially the same size. To DOS, this is 5 megabytes; to the p-System, it's over 10,000 blocks. Either partition is bootable; the partition table indicates which one the bootstrap is to use. It is changed with FDISK.CODE when under the p-System, or with FDISK.COM when under DOS.

PCNFS.SYS takes between 64 and 90K of RAM, so on most of the 386 machines, it's loaded into high ("adapter", "upper", trans-640k) memory -- at least when the memory re-arrangements worked out for them provide a contiguous space large enough. This can make a significant difference to the amount of conventional memory available for programming environments.
Note that its ancillary files, SOCKDRV.SYS (the socket driver) and WD8003E.SYS (the driver for the Western Digital ethernet board) cannot function if loaded into high memory.

The WD8003E ethernet adapter card needs 8K of RAM in the area between 640K and 1 megabyte.
On the ISA-bus 386 machines, it is placed at segment address B000, which is between the video buffers for, respectively, graphics and text. (This space is used for buffering monochrome text on machines that use monochrome monitors. None of the machines now in active use at the Center do so.) This leaves enough contiguous RAM above the video buffers both to allocate the page frame (64K) for expanded memory, and to load PCNFS.SYS high. But the reference diskette for the MicroChannel machines, by which all adapter configuration has to be done, so far permits no lower an address than C000, which leaves too little contiguous space to load PCNFS.SYS high.

Sun's WD8003E.SYS doesn't drive the WD8003E/A; nor does Western Digital have an NFS-compatible driver for that board. WD8003E.SYS is therfore replaced on our MicroChannel systems with the PC-NFS Driver Compatibility Kit (note this version may be outdated):

1. 3Com's and Microsoft's (at the time) L.A.N.Manager LANMAN.SYS, and its protocol manager, PROTMAN.SYS and configuration file PROTMAN.INI;
2. Western Digital's MacWD driver, MACWD.SYS, which is compatible with the WD8003E/A; in 1990 it was available on Western Digital's public BBS at either 714-852-8951 or 714-756-8176.
3. and NFS-NDIS, to adapt NFS calls to these drivers. NDIS, Network Distribution Interface Standard, is a networking standard that both the LANManager system and MACWD.SYS understand.

Some points about the MicroChannel:

• Apparently by convention, all cards and adapters for installation into MicroChannel Architecture machines have "/A" following their root names.
  
• Since the Microchannel requires all adapters plugged into it to handle bus-mastering, and to cooperate with reporting and reconfiguration of their parameters by software, these adapters are not interchangeable with the more common ISA adapters. Nor can they be expected to be interchangeable with adapters for the Intel PCI standard.
• The software configuring of the adapters in a PS/2 machine, mentioned above, is done by booting on the so-called reference diskette whose original (never change it!) comes with the PS/2; and whose working copy (never lose it!) is used to update and record the new configuration of the individual machine every time a change is made to its adapters.
  It is not, in fact, fatal to lose the working reference disc, as a new copy of the original can update its information from the PS/2 it's booted on; but this is risky and may lose important information, especially if any settings had to be altered by hand after trial and error.
• Note that, in the author's experience, no jumpers or switches have ever had to be located or changed on a MicroChannel adapter. At the same time, locating a MicroChannel version of an adapter the lab needs to purchase can be very chalenging.