Comment by Suzuran

Could be. You could also have been thinking of the 11/730, which was a cost-reduced 11/750 and thus the second-slowest VAX model DEC ever sold.

The slowest would be the 11/725, which was a cost-reduced 11/730 that had a reduced clock speed and half of the bus slots filled with epoxy to limit expansion. The 11/725 was so slow that using it was an act of masochism; It was slower than your 11/23+.

Those models were pretty rare though. Even though they were cheaper than an 11/750 the performance drop from the 750 to the 730 was too severe to justify even the reduced cost. If that were all then maybe replacing PDP-11s being used in industrial applications might have saved it but the 730 was still too expensive versus the existing PDP-11 products, and the 725's limited expansion made it less attractive than those same PDP-11 products. The PDP-11 thus outlived both the 725 and the 730.