What this 74ABT640 inverting transceiver is for
It uses 3-state outputs so you can connect it directly to a shared backplane or memory bus without contention.
32 mA source, 64 mA sink — what that drive buys you
The output drive is rated at 32 mA for the high level and 64 mA for the low level. That sink current is double the source, which matches the typical bus load where the low-level fan-out is the tighter constraint. If you're driving a heavily loaded 5V backplane or a long ribbon cable, this part can handle the current without needing a separate buffer. The 3-state outputs let you float the bus when the transceiver is not selected, which is how you wire up multiple cards on the same data lines.
That means Texas Instruments is still manufacturing it, and there's no last-time-buy window closing. For a repair bench or a production BOM that needs this exact inverting transceiver, you're not forced into the surplus channel yet. The 74ABT series has been around for years, so date codes may vary, but the part is still a standard catalog item.
Industrial temperature range — not just an office part
If your system lives in a conditioned server room, the commercial-grade 74ABT parts would also work, but the industrial rating gives you margin.