Rocksolid Light

Welcome to novaBBS (click a section below)

mail  files  register  newsreader  groups  login

Message-ID:  

6 May, 2024: The networking issue during the past two days has been identified and appears to be fixed. Will keep monitoring.

devel / comp.arch / Why use register renaming when ROB is present?

SubjectAuthor
* Why use register renaming when ROB is present?Zach
+- Re: Why use register renaming when ROB is present?robf...@gmail.com
+- Re: Why use register renaming when ROB is present?MitchAlsup
`- Re: Why use register renaming when ROB is present?Quadibloc

1
Why use register renaming when ROB is present?

<dc6b5e39-59f5-4d22-bde6-7679335bbf61n@googlegroups.com>

  copy mid

https://www.novabbs.com/devel/article-flat.php?id=30408&group=comp.arch#30408

  copy link   Newsgroups: comp.arch
X-Received: by 2002:a05:620a:13f0:b0:706:702e:bab7 with SMTP id h16-20020a05620a13f000b00706702ebab7mr94971qkl.579.1673862477412;
Mon, 16 Jan 2023 01:47:57 -0800 (PST)
X-Received: by 2002:a05:6870:42d2:b0:144:9878:46be with SMTP id
z18-20020a05687042d200b00144987846bemr6972312oah.245.1673862477087; Mon, 16
Jan 2023 01:47:57 -0800 (PST)
Path: i2pn2.org!i2pn.org!usenet.blueworldhosting.com!feed1.usenet.blueworldhosting.com!peer01.iad!feed-me.highwinds-media.com!news.highwinds-media.com!news-out.google.com!nntp.google.com!postnews.google.com!google-groups.googlegroups.com!not-for-mail
Newsgroups: comp.arch
Date: Mon, 16 Jan 2023 01:47:56 -0800 (PST)
Injection-Info: google-groups.googlegroups.com; posting-host=2a02:587:723f:a900:389f:ae74:f251:90ce;
posting-account=BibRVQoAAADhxHJ3-P_4-nNWEb2rsfDK
NNTP-Posting-Host: 2a02:587:723f:a900:389f:ae74:f251:90ce
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <dc6b5e39-59f5-4d22-bde6-7679335bbf61n@googlegroups.com>
Subject: Why use register renaming when ROB is present?
From: zast...@gmail.com (Zach)
Injection-Date: Mon, 16 Jan 2023 09:47:57 +0000
Content-Type: text/plain; charset="UTF-8"
X-Received-Bytes: 1273
 by: Zach - Mon, 16 Jan 2023 09:47 UTC

What are the benefits of using register renaming by mapping logical register to physical registers, when Tomasulo's algorithm is used with ROB, considering the fact that by using the ROB, any name dependencies (WAW, WAR) are eliminated?

Re: Why use register renaming when ROB is present?

<9188ff08-8146-41ef-99e4-786e11a7e14an@googlegroups.com>

  copy mid

https://www.novabbs.com/devel/article-flat.php?id=30416&group=comp.arch#30416

  copy link   Newsgroups: comp.arch
X-Received: by 2002:a05:620a:6db:b0:6ef:1b80:ac9b with SMTP id 27-20020a05620a06db00b006ef1b80ac9bmr2773360qky.773.1673877165905;
Mon, 16 Jan 2023 05:52:45 -0800 (PST)
X-Received: by 2002:a05:6808:d51:b0:35c:27c2:68a4 with SMTP id
w17-20020a0568080d5100b0035c27c268a4mr6991392oik.42.1673877165602; Mon, 16
Jan 2023 05:52:45 -0800 (PST)
Path: i2pn2.org!i2pn.org!weretis.net!feeder8.news.weretis.net!newsreader4.netcologne.de!news.netcologne.de!peer02.ams1!peer.ams1.xlned.com!news.xlned.com!peer01.iad!feed-me.highwinds-media.com!news.highwinds-media.com!news-out.google.com!nntp.google.com!postnews.google.com!google-groups.googlegroups.com!not-for-mail
Newsgroups: comp.arch
Date: Mon, 16 Jan 2023 05:52:45 -0800 (PST)
In-Reply-To: <dc6b5e39-59f5-4d22-bde6-7679335bbf61n@googlegroups.com>
Injection-Info: google-groups.googlegroups.com; posting-host=99.251.79.92; posting-account=QId4bgoAAABV4s50talpu-qMcPp519Eb
NNTP-Posting-Host: 99.251.79.92
References: <dc6b5e39-59f5-4d22-bde6-7679335bbf61n@googlegroups.com>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <9188ff08-8146-41ef-99e4-786e11a7e14an@googlegroups.com>
Subject: Re: Why use register renaming when ROB is present?
From: robfi...@gmail.com (robf...@gmail.com)
Injection-Date: Mon, 16 Jan 2023 13:52:45 +0000
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Received-Bytes: 2433
 by: robf...@gmail.com - Mon, 16 Jan 2023 13:52 UTC

On Monday, January 16, 2023 at 4:47:58 AM UTC-5, Zach wrote:
> What are the benefits of using register renaming by mapping logical register to physical registers, when Tomasulo's algorithm is used with ROB, considering the fact that by using the ROB, any name dependencies (WAW, WAR) are eliminated?

Good homework question. I cannot think of any benefits ATM for a Tomasulo’s algorithm combined with ROB machine.

My somewhat limited understanding is that you are correct that dependencies are eliminated and the ROB effectively supplies new names for registers in the form of a ROB entry index. Operands are managed in terms of ROB entries which is a sort of renaming. So additional renaming is not needed. I think the out-of-order RiSC-16, Prof. Bruce Jacob, covers this. A few years ago I took the RiSC-16 and added explicitly renamed registers then found out it did not make any difference. I think explicit renaming comes into play when a different algorithm is used or the ROB is not used. Not all machines use Tomasulo’s plus ROB. But I maybe missed something as my experience is limited.

Re: Why use register renaming when ROB is present?

<9a9aac8a-a131-4c41-94a2-e1dfede863e9n@googlegroups.com>

  copy mid

https://www.novabbs.com/devel/article-flat.php?id=30423&group=comp.arch#30423

  copy link   Newsgroups: comp.arch
X-Received: by 2002:a05:622a:5d83:b0:3b6:2bb2:216c with SMTP id fu3-20020a05622a5d8300b003b62bb2216cmr255785qtb.616.1673892745126;
Mon, 16 Jan 2023 10:12:25 -0800 (PST)
X-Received: by 2002:a05:6870:9e8a:b0:15e:b02f:dfdc with SMTP id
pu10-20020a0568709e8a00b0015eb02fdfdcmr51529oab.118.1673892744762; Mon, 16
Jan 2023 10:12:24 -0800 (PST)
Path: i2pn2.org!i2pn.org!weretis.net!feeder8.news.weretis.net!proxad.net!feeder1-2.proxad.net!209.85.160.216.MISMATCH!news-out.google.com!nntp.google.com!postnews.google.com!google-groups.googlegroups.com!not-for-mail
Newsgroups: comp.arch
Date: Mon, 16 Jan 2023 10:12:24 -0800 (PST)
In-Reply-To: <dc6b5e39-59f5-4d22-bde6-7679335bbf61n@googlegroups.com>
Injection-Info: google-groups.googlegroups.com; posting-host=2600:1700:291:29f0:d52a:4d1b:1d68:bdd0;
posting-account=H_G_JQkAAADS6onOMb-dqvUozKse7mcM
NNTP-Posting-Host: 2600:1700:291:29f0:d52a:4d1b:1d68:bdd0
References: <dc6b5e39-59f5-4d22-bde6-7679335bbf61n@googlegroups.com>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <9a9aac8a-a131-4c41-94a2-e1dfede863e9n@googlegroups.com>
Subject: Re: Why use register renaming when ROB is present?
From: MitchAl...@aol.com (MitchAlsup)
Injection-Date: Mon, 16 Jan 2023 18:12:25 +0000
Content-Type: text/plain; charset="UTF-8"
 by: MitchAlsup - Mon, 16 Jan 2023 18:12 UTC

On Monday, January 16, 2023 at 3:47:58 AM UTC-6, Zach wrote:
> What are the benefits of using register renaming by mapping logical register to physical registers, when Tomasulo's algorithm is used with ROB, considering the fact that by using the ROB, any name dependencies (WAW, WAR) are eliminated?
<
Tomasulo manages register data-flow for calculation instructions with OoO execution.
The ROB is present for precise exceptions and interrupts.

Re: Why use register renaming when ROB is present?

<31b0e2ad-4ad4-4152-9449-196373d96fd2n@googlegroups.com>

  copy mid

https://www.novabbs.com/devel/article-flat.php?id=30457&group=comp.arch#30457

  copy link   Newsgroups: comp.arch
X-Received: by 2002:a0c:c392:0:b0:534:ec18:6e1b with SMTP id o18-20020a0cc392000000b00534ec186e1bmr308526qvi.43.1674022382762;
Tue, 17 Jan 2023 22:13:02 -0800 (PST)
X-Received: by 2002:a54:4e8a:0:b0:363:f1fb:f580 with SMTP id
c10-20020a544e8a000000b00363f1fbf580mr372943oiy.201.1674022382434; Tue, 17
Jan 2023 22:13:02 -0800 (PST)
Path: i2pn2.org!i2pn.org!usenet.blueworldhosting.com!feed1.usenet.blueworldhosting.com!peer01.iad!feed-me.highwinds-media.com!news.highwinds-media.com!news-out.google.com!nntp.google.com!postnews.google.com!google-groups.googlegroups.com!not-for-mail
Newsgroups: comp.arch
Date: Tue, 17 Jan 2023 22:13:02 -0800 (PST)
In-Reply-To: <dc6b5e39-59f5-4d22-bde6-7679335bbf61n@googlegroups.com>
Injection-Info: google-groups.googlegroups.com; posting-host=162.157.97.93; posting-account=1nOeKQkAAABD2jxp4Pzmx9Hx5g9miO8y
NNTP-Posting-Host: 162.157.97.93
References: <dc6b5e39-59f5-4d22-bde6-7679335bbf61n@googlegroups.com>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <31b0e2ad-4ad4-4152-9449-196373d96fd2n@googlegroups.com>
Subject: Re: Why use register renaming when ROB is present?
From: jsav...@ecn.ab.ca (Quadibloc)
Injection-Date: Wed, 18 Jan 2023 06:13:02 +0000
Content-Type: text/plain; charset="UTF-8"
X-Received-Bytes: 2136
 by: Quadibloc - Wed, 18 Jan 2023 06:13 UTC

On Monday, January 16, 2023 at 2:47:58 AM UTC-7, Zach wrote:
> What are the benefits of using register renaming by mapping logical
> register to physical registers, when Tomasulo's algorithm is used with
> ROB, considering the fact that by using the ROB, any name
> dependencies (WAW, WAR) are eliminated?

I can't answer your question, but I can give you some background.

While IBM's 360/91, and the other machines derived from it
(360/95, 360/195, 370/195) used Tomasulo's algorithm in its
original form, with Reservation Stations, nearly every other
computer designed by anyone else that provided equivalent
out-of-order execution capabilities used register renaming
instead.

I doubt that it has "benefits", in the sense that the register renaming
approach allows out-of-order execution to be more efficient. Instead,
I think it's more likely that the register renaming approach is just
simpler to implement. Either that, or it was only a way to avoid some
IBM patents.

John Savard

1
server_pubkey.txt

rocksolid light 0.9.81
clearnet tor