NETRATE

Syntax NETRATE transmit_delay, reception_delay, timeout
Location FLEXYNET (DIY Toolkit - Vol Y)

This command is at the heart of the Flexynet philosophy and allows you to alter the speed of the QL’s networks (as regards NETSEND and NETREAD), so that you can match the speed of the network ports to the various computers which are linked together over the network. This enables different machines to talk to each other substantially more quickly than using the Network drivers supplied with the QL or Toolkit II.

Values are sent over the Network ports as pulses equivalent to bits, with eight bits representing one byte (0…255) - the pulse is an electrical signal, either 1 or 0 (on or off). The three parameters are all in arbitrary units and if they are specified as zero, any existing value will remain unchanged. They are used as follows:

  • Transmit_delay - this specifies the amount of time that the sending machine will alter the voltage for on the network to signify either a 1 or a 0 bit. This needs to be higher than the reception delay on the receiving machine as the receiving process is fundamentally slower than the transmission process. The higher the value, the longer the delay.

  • Reception_delay - this specifies the amount of time Flexynet will wait for changes in the voltage over the network ports.

    If the change occurs after Flexynet has counted up to the reception_delay value, then a bit of 0 is assumed, otherwise a bit of 1. Once eight bits have been received then a byte made up of those eight bits is stored in memory. For example: CHR$(10) is represented by the bits 0 0 0 0 1 0 1 0 This can be seen by:

    PRINT BIN$ (10,8)
    
  • Timeout - this represents a timing loop which Flexynet will wait for the next pulse over the net - if nothing is received in this time, then a ‘not complete’ error will be reported. This value will need to exceed the reception_delay parameter by a comfortable margin. The easiest way to match up the required parameter values for two machines connected using Flexynet is to send a copy of one machine’s screen to the other machine and compare the display. To do this, enter the command:

    NETREAD 131072,32768
    

    on the receiving machine, then enter the command:

    NETSEND 131072,32768
    

    on the sending machine.

    If the NETRATE parameters are incorrect, you will notice that the displays do not match - either increase the reception_delay on the receiving machine or increase the transmit_delay on the sending machine, making notes of the values which you have tried at either end.

It is difficult to give any advice on the parameters to use as it depends on the expansion boards being used with your particular QL, as well as the speed of the ZX-8301 chip which forms part of the QL’s motherboard. However, the author cites the following test results:

  • Standard QL to Standard QL (both with code in ROM or fast RAM such as CST 512K expansion board):

    NETRATE 5,3,127
    

    on both machines

  • Gold Card on British QL to Gold Card on Foreign QL:

    NETRATE 8,4,0
    

on both machines.

  • Gold Card on Foreign QL to Gold Card on British QL:

    NETRATE 33,12,0
    
on both machines
  • Standard QL (with code in ROM or fast RAM such as CST 512K expansion board) to Gold Card on Foreign QL:

    NETRATE 2,2,127
    

    on the Standard QL:

    NETRATE 20,7,127
    

    on the Gold Card QL

NOTE

Flexynet will not work on machines which do not use a 68000 or 68008 chip (for example QXLs or Super Gold Card), unless the Cache is disabled (see CACHE_OFF). It also requires an expanded machine to work properly.

CROSS-REFERENCE

Refer to the Networks Appendix for further details. See NETVAR% which allows you to read the various speed settings. Also see NETREAD and NETSEND