@User It is a not-significant amount of effort to make 9-track versions as well. I see tasks related to this listed on our Jira. I would say it would be only a week and a half of focused work to get 9-track cells all the way through design, testing, and characterization in select target corners. I am not sure about a 7.4-track version matching hd; I don't see any internal documentation about its feasibility, so it is unknown how difficult it would be to create.

I actually have just a few aux. cells (a handful) that I would need to make larger which is even better! Just curious do you have the FO4 delay of all these libs?

I have characterization datasheets (like this HTML file: https://foss-eda-tools.googlesource.com/skywater-pdk/libs/sky130_osu_sc_t18/+/refs/heads/mai[…]18T_ms_TT_1P8_25C.ccs/SKY130_OSU_SC_18T_MS__INVx.html ), but I don't have FO4 off-hand. I can run sims over the weekend to get those specs.

My observation is that it is a lot of trouble to use the HD cells, was a lot of work to get the OpenROAD tools to insert the tap cells properly, is a constant pain with people not used to the tools not knowing that they need tap cells, or putting the tap cells at the wrong distance. . . And in the end, the design has to be padded with 60% fill to get it to route. So what was the point of the high density? Just causes a lot of pain and trouble.

@User Hi! were you able to simulate the FO4 delay and compare?

Sorry @User, last week of the semester has been crazy. I did a FO4 set-up with just the x1 drive cells from each library, The SkW cells, I connected their VNB and VPB pins directly to the rails, which may be a little unrealistic, but probably not too much. This is the table I got out: Cell library Averaged FO4 delay (ns) sky130_fd_sc_hd 0.03457 sky130_fd_sc_hs 0.031975 sky130_osu_sc_18T_hs 0.051365 sky130_osu_sc_18T_ms 0.05408 sky130_osu_sc_18T_ls 0.055905 sky130_osu_sc_15T_hs 0.055215 sky130_osu_sc_15T_ms 0.056715 sky130_osu_sc_15T_ls 0.05753 sky130_osu_sc_12T_hs 0.05413 sky130_osu_sc_12T_ms 0.057105 sky130_osu_sc_12T_ls 0.059195

Thanks! @User

The SkW cells, I connected their VNB and VPB pins directly to the rails, which may be a little unrealistic, but probably not too much.

They need to be right? you can't leave them hanging.

I just realized, one big difference is that the OSU ones were run with PEX, the scs8 ones were run without. My mistake. Let me re-run and see if that changes anything.

Thanks! I am curious to see the difference you see after running with PEX. Thanks a lot for taking the time to do this!

They need to be connected, yeah. I just imagine that simulating the effect of the tap cells, with some wire delay artificially added, may be more effective. I'll run the PEX alternatives after I get out of my current class. Sorry that I got so wrapped up this week. Project deadlines.

sounds good! and good luck with that! You just need to connect VNB/VPB on the extracted spice to vdd/gnd. No tapecell is needed for the fo4 delay 🙂

Yeah, that's the way I have it done.

can you share more details on the simulator etc.. and it is weird that hd is tiny bit faster than hs

Absolutely! Let me private message you the SPICE decks and the spreadsheet.