That's a new one to me too. Only reference I can see is something to do with the internal name of a Winbond chipset for 486 Amstrad MegaPC.

On a totally unrelated topic, it still tickles me pink to see my Alt12887 in use. 😁

Ohh yeah these rtc replacements are awesome thanks for them!!!
Funny - I will use this board to upgrade a mega pc 😀

sorry to further derail, but why use this instead of a new production Dallas RTC chip?

Better to replace a battery instead of an entire new module every few years.

^ exactly, I have no interest sourcing DALLAS RTC clock chips of questionable quality/origin when a modern replacement is available 😀

Aaron G. on facebook knew what WINBUS is and wrote this comment:

The Winbus is the memory area for onboard VGA framebuffers, its marked as "reserved conventional memory", if using external video card, the area can be mapped and used by dos (himem.sys) for expanding memory. Its been a long time since I built machines with these boards in them. So basically its an early version of integrated video.

so mystery solved! 😀

OK I think I found it - WINBUS is about the onboard VGA internal connection to the chipset or what Winbond calls their "VLB variant" .

There are 2 jumpers labeled ISA and VLB. This setting affects VGA speed.
- with ISA setting SpeedSys reports 2282 kb/sec VRAM speed and Wolf3D timedemo reports 23,7fps
- with VLB setting SpeedSys reports 3085 kb/sec VRAM speed and Wolf3D timedemo reports 29,50fps , WINBUS gets auto-configured at "Middle Timing"

I'll do some stability tests but I think all will be OK.