Don't know if you have seen this - might be helpful http://www.quadibloc.com/comp/cp0306.htm
On Tue, Mar 2, 2021 at 3:09 PM Kyle Owen via cctalk <cctalk@classiccmp.org> wrote: > > Has anyone noticed a difference in DVI overflow behavior on the PDP-8/I EAE > versus the PDP-8/E EAE? The 8/E EAE claims to be 8/I compatible in Mode A, > and I think I agree, for the most part. At least, it's compatible for the > parts that matter. > > When a DVI instruction results in overflow, the EAE immediately returns > with the link set. The results in AC and MQ seem to have no relevance, but > they appear to differ between the 8/E and 8/I. > > For instance, running the 8/I MUY/DVI diagnostics under SimH fails due to > the following: > > sim> lo maindec/maindec-8i-d0ba-pb.bin > sim> d sr 40 > sim> g 201 > > > > DIVERR L C(AC) C(MQ) C(MB) > > PROB 0 000000000000 000000000000 000000000000 > > GOOD 1 111111111111 000000000000 000000000000 > BAD 1 000000000000 000000000001 000000000000 > > SCA 000000000000 > > HALT instruction, PC: 01512 (JMP I 1506) > > The link is set, but obviously MQ and AC do not match. > > Running the same diagnostic on an 8/I works fine. > > I can't imagine a scenario outside of diagnostics where this behavior would > impact the software, but it does seem curious nevertheless that the DVI > approach to handling overflow differs slightly between EAEs on the 8/I and > 8/E. > > Kyle
