Is that the FPU that the XLerator uses?
Is the ESCC Lisa specific or off the shelf?
The FPU used by the original 16 MHz XLerator is the MC68881RC16 or MC68882RC16. These are currently available as new-old-stock from Rochester electronics
https://www.rocelec.comNote that the FPU
DOES NOT improve XLerator performance except in very specific circumstances, so they are generally not worth the price.
The 85230 ESCC in the DIP package is a generic part (not Lisa specific).
The 85230 ESCC differs from the 8530 SCC in mostly subtle ways; the feature that can make a difference in a performance-limited situation (such as a stock Lisa) is that the FIFO buffer is 5 characters vs 3 characters.
The peer-to-peer file server feature that arrived in System 7 requires more performance than the LocalTalk client. With the stock SCC, a 5 MHz Lisa does not have sufficient performance to be a LocalTalk file server (but can act as a client as it does with System 6).
When developing MW+II it seemed that the ESCC helped to improve the reliability of LocalTalk in a stock Lisa, hence the mention in the documentation.
However, from out-in-the-wild reports in the years since then, it isn't clear in what circumstances the ESCC affects LocalTalk -- the suspicion is that it is dependent on the specific devices on the network.
The most dramatic improvement in LocalTalk comes from better CPU performance, eg. an XLerator (or perhaps one day an FPGA-Lisa). With an accelerator, it appears the SCC is always sufficient.
Note that the E/SCC does not affect the use of Ethernet, which is often a better method of networking under MW+II.
