File CONFIG.SYS

The CONFIG.SYS file serves to configure various DOS parameters as DOS boots, and to load and run device drivers. The CONFIG.SYS file for ZY102 looks like this:

  stacks=8,512
  device=c:\dos\himem.sys
  device=c:\dos\emm386.exe ram
  buffers=20
  files=20
  dos=umb
  dos=high
  lastdrive=b

  rem Network NDIS drivers
  device=c:\bin\ndis\protman.dos /I:c:\bin\ndis
  devicehigh /L:3,5984=c:\bin\ndis\dis_pkt.gup
  devicehigh /L:3,10160=c:\bin\ndis\elnkii.dos

A line by line description follows:

stacks=8,512: Sets the number of hardware stacks that will be used by ISRs when they interrupt DOS.

device=c:$\backslash$dos$\backslash$himem.sys: Loads the Extended Memory (XMS) Manager. Extended memory is the memory addressed beyond the 1 MByte address space of ``real-mode'' DOS.

device=c:$\backslash$dos$\backslash$emm386.exe ram highscan: Loads the Expanded Memory Manager (EMM). The EMM manages the Upper Memory Blocks (UMB), which are blocks of free memory between the 640 KByte address and the 1 MByte address, and also manages Expanded Memory Specification (EMS) version 3.0 and 4.0 memory, implemented using the PC's extended memory. ZY version 2.5 and later require EMS 3.0 memory.

buffers=20: Sets the number of buffers to use when performing file I/O. Large numbers increase performance, lower numbers conserve memory. Unlike the files parameter, this parameter is not used by PC/TCP, which provides its own buffers. The ZY does not perform much file I/O, therefore this number can probably be decreased.

files=20: DOS will allocate 20 file handles. Although the ZY will not be opening 20 files, PC/TCP uses one file handle per socket, so there need to be enough handles to satisfy the requirements of the ZY, which opens some files and at least 2 sockets.

dos=umb: Instructs DOS to manage the UMB area.

dos=high: Instructs DOS to load itself high, thus freeing memory in the all-important 0-640 KByte zone.

lastdrive=b: Tells DOS that the last drive mounted on the system is drive B. This saves memory, as otherwise DOS will be prepared for the possibility of drives A-Z.

device=a:$\backslash$NDIS$\backslash$protman.dos /I:a:$\backslash$NDIS: Loads and runs the protocol manager (see figure A.2). Note the parameter /I:a:$\backslash$NDIS, which tells the protocol manager PROTMAN.DOS where to find the configuration file PROTOCOL.INI.

devicehigh /L:3,5984=a:$\backslash$NDIS$\backslash$dis_pkt.gup: Loads and runs the NDIS to packet driver converter (see figure A.2). Because of the devicehigh command, DOS will attempt to load this driver in the UMB area. See the DOS on-line help utility for more information.

devicehigh /L:3,10160=a:$\backslash$NDIS$\backslash$elnk3.dos: Loads and runs the EtherLink III NDIS driver. Because of the devicehigh command, DOS will attempt to load this driver in the UMB area. See the DOS on-line help utility for more information.

The three network drivers PROTMAN.DOS, DIS_PKT.GUP, and ELNK3.DOS must be loaded in the order shown, or the system will not be able to communicate[21].