Another DCJ11 oddity

Thanks for that pointer; I don't think I've ever seen that - quite interesting. Alas, it didn't have the cache info - but now that I've though about it overnight, I'm pretty sure the reason for the two bits that do the same thing is for -11/70 compatability. Yes, the DCJ11 cache is quite interesting, the way the functionality is partitioned between the chip itself, and external circuitry; the actual cache data is stored externally, along with the tags, parity, etc, and also the CPU and DMA comparators. The KDB11-A and -B differ a bit in their cache; both are single-associative (i.e. only one cache cell for each word), but the -B has duplicate tag arrays, one for the CPU's use, one for DMA devices - apparently so that contention between the two for access to the tags doesn't slow things down (since the tag stores are memory arrays, they need to do an address-input before any tag can be checked). Yes, I only found that out last night (or maybe I saw it on a previous scan of the manual, but its importance didn't register). The -11/70 doesn't have that! Very useful for my application (a memory tester program)... Noel