PDP-8/I vs 8/E EAE

[Bob Smith]

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 at 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