[Simh] [OT] What's the difference between the 1990 Brunner VAX Architecture book and the Leonard from 1987?

[Paul Koning]

> On Jan 28, 2016, at 5:28 AM, lists at openmailbox.org wrote:
> 
> Hi,
> 
> Since there are some ex-DEC people here and many people knowledgeable in
> VAX can anybody tell me the [major] differences between these books if any?
> The Brunner book is very expensive, the 1987 copy is very affordable. What
> do I miss out on by buying the one by Timothy Leonard from 1987?
> 
> I realize the scans are up on bitsavers but I usually find real books
> easier to deal with.

I assume by "Brunner book" you mean the copy of DEC Std 032, the VAX Architecture Standard.  And "Leonard book" is the "VAX Architecture Reference Manual" edited by Tim Leonard, published by Digital Press.

Ok...  The DEC Std is a DEC internal document, labeled as such.  Some DEC standards were considered quite sensitive, and issued as numbered, individually-tracked documents.  I had one such for Alpha, which I duly returned to the document custodian when I left.

The DEC Std is the full, authoritative description of what a VAX is.  If you want to build a VAX (a new design, not a clone of an existing one), that document will tell you how to do so.  If you do everything it says, the result *should* be a correct VAX implementation, and VAX software should run on it.  

(This is the "conformance implies interoperability" principle of standard design.  This was the definition of proper standards design that was used at DEC.  For example, if you want to implement DDCMP, all you have to do is carefully code what the DDCMP spec say, and if you do so, it WILL work.   Unfortunately, most of the rest of the world does not believe in this level of quality.  I was involved at one point in IETF standards work, and I mentioned this principle in a meeting.  The document editor actually objected to what I said and stated that it was unreasonable to expect protocol standards to do this.  And sure enough, the document he produced is NOT good enough that you can just do what it says and expect the result to be a working implementation -- you have to hack on it and test against other implementations to come up with the right combination of hacks and tweaks and bug workarounds for things to work.  Sigh.)

On the other hand, the Digital Press book is a public document.  Its purpose is to describe to VAX *users* what a VAX is.  If you want to port an OS, or a compiler, to VAX, you'll want this book.  If you want to write applications for VAX, it will certainly work as well (though it might be more than you need).

In other words, the book is a subset of the DEC Std.  If you want the ultimate reference, grab the standard.  If you want to debug an emulation (say, if there is debate about whether SIMH gets the VAX correct), the DEC Std will be the authority to settle the question. For other software work -- say, the NetBSD port for VAX, or the VAX backend of GCC -- the published book is likely to be sufficient.

	paul