Re: Looking for a garbage collection paper

gah4 <gah4@u.washington.edu>
Thu, 29 Sep 2022 23:56:42 -0700 (PDT)

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Re: Looking for a garbage collection paper gah4@u.washington.edu (gah4) (2022-09-29)
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From: gah4 <gah4@u.washington.edu>
Newsgroups: comp.compilers
Date: Thu, 29 Sep 2022 23:56:42 -0700 (PDT)
Organization: Compilers Central
References: 22-09-011 22-09-012 22-09-013 22-09-014 22-09-016 22-09-022
Injection-Info: gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="16871"; mail-complaints-to="abuse@iecc.com"
Keywords: architecture, history, comment
Posted-Date: 30 Sep 2022 21:31:52 EDT
In-Reply-To: 22-09-022

On Thursday, September 29, 2022 at 9:40:59 PM UTC-7, gah4 wrote:


(snip)


> But not if index registers are different from other registers, like
> (if I remember) they are on the 7090.


> [Yes, the 704 series had separate index registers. It occurs to me that
> another way to do this is to use the rotate instructions the 70x and PDP-6/10
> had. Since the word is 36 bits, you rotate by 12 each time and you'll have
> three bit patterns. -John]


or a ROTC double word rotate on the PDP-10 by 24, with 18 bit addressing
and indexing.


I am not sure about rotate on the 709 or 7090.


Also, for those machines, I suspect a 12 bit shift or rotate takes 12 cycles.
They didn't have enough logic for a barrel shifter, like many machines now have.
Might be slower than more than one fast instruction.
[The 709x had a rotate instruction but this archaeology is a bit far from compilers. -John]

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