[Info-vax] Volatile, was: Re: yet another sys$qiow question

[Johnny Billquist]

On 2015-08-24 22:34, George Cornelius wrote:
> In article <mr792b$f9l$1 at Iltempo.Update.UU.SE>, Johnny Billquist <bqt at softjar.se> writes:
> [VAXMAN wrote:]
>
>>> 	TSTL	IOSB
>>> 	BNEQ	10$
>>> 20$:	BRB	20$
>>> 10$:
>
> Actually, to test just the status in VMS you would use TSTW.  But
> when testing for nonzero TSTL works as well and does not require
> any extra word extraction code on the newer architectures.

Good point.

> TSTW is precisely what the PDP-11 code would be, but in that case the
> IOSB has only two words, one of which is status.

Yep. Life is simpler under RSX. :-)

>> Yeah, I suspected it should look like that, it's just that I have not
>> programmed in Macro-32 in many years, and instead of feeling foolish for
>> doing something stupid with some mnemonic, I stayed with what I know
>> even in my sleep, and expect you to rescue me. :-)
>>
>> (There are just so many variants of the instructions on the VAX...)
>
> The ultimate CISC implementation for quite a few years.  Surprising to
> see polynomial evaluation as a single instruction, for example.

Indeed.

> By comparison, without autoincrement/autodecrement and non- at Rn
> indirection, the PDP-11 was almost RISClike.

Yeah. But I still got bitten a few times by things I'm used to on a 
PDP-11 that don't work on a VAX.
But in general, the VAX makes things easy...

But I really like having the PC being a general register. (Yes, I know 
it sortof is on the VAX, but you cannot do random arithmetic on it... 
Can't remember if it is allowed, but that variable instruction lengths 
makes it hard to be useful anyway... :-) )

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol