32-bit Econet Module
The 32-bit version of the Econet module is slightly smaller than the earlier Master Series version. The connecting pins are much shorter allowing the module to sit much nearer to the motherboard than the 8-bit version.
With the exception of the 68B54, all the components have been replaced with surface mount components.
I initially thought that the space at IC4 and the four unused link positions nearby were for adding clock circuitry.
However, this is not the case: according to the circuit diagram published in the Econet Design & Installation Guide (Acorn, 1993), IC4 is for a 26LS30, the same as IC7. This is one of the line drivers in the Econet interface, which can be damaged or destroyed by mains interference.
Presumably the provision of space for the through-hole version of this chip would allow for easier replacement if the surface mount one blew. There isn't any information given specifically about what the four links points do, but looking at the circuit diagram - and I'm no expert on these things - it looks to be a way of re-routing the circuit from IC7 to IC4 in the event that the replacement chip is being used.
This type of Econet interface was introduced originally for the A3020 and A4000 machines which had limited space inside them and would not accommodate a podule expansion if the older Master Series type is used.
Above you can see a picture of two different coloured 32-bit Econet modules. It looks as if the gold/brown coloured one was earlier if you look at the serial number but apart from the colour there is no difference between the two.
Although this type was made for the 32-bit machines, I can confirm that it works perfectly on the BBC Master. I have tested one of these extensively inside Station 1 without any problems at all. You can't use the Master Series mounting pegs as they are too tall but apart from this there is no difficulty. This type could be used, for example, in applications where you want to use a ROM expansion board which would get in the way of the Econet module. In the past I have had to build up expansion boards using extra 28-pin ROM sockets to clear the Econet module. This way is much easier.