| Deutsch English Français Italiano |
|
<bf04e43a5fe6e52b68bc414893fcf8bd@www.novabbs.org> View for Bookmarking (what is this?) Look up another Usenet article |
Path: ...!news.misty.com!weretis.net!feeder9.news.weretis.net!i2pn.org!i2pn2.org!.POSTED!not-for-mail
From: mitchalsup@aol.com (MitchAlsup1)
Newsgroups: comp.arch
Subject: Re: Oops (Concertina II Going Around in Circles)
Date: Thu, 9 May 2024 21:08:48 +0000
Organization: Rocksolid Light
Message-ID: <bf04e43a5fe6e52b68bc414893fcf8bd@www.novabbs.org>
References: <kipj2j5be9kuv8rn770iq6neq2cvu3s5oi@4ax.com> <b936220e0d198db43b18e58007401f42@www.novabbs.org> <6qam3jplo8oa9n46g70c48tn69ao8hn486@4ax.com> <ee4741388de9887010e58dd1e2770a7c@www.novabbs.org> <ksdo3jd4bia075pulpohgv4upabfq1h0e4@4ax.com> <0L9%N.64235$iMKd.13473@fx12.iad>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Info: i2pn2.org;
logging-data="605268"; mail-complaints-to="usenet@i2pn2.org";
posting-account="65wTazMNTleAJDh/pRqmKE7ADni/0wesT78+pyiDW8A";
User-Agent: Rocksolid Light
X-Rslight-Posting-User: ac58ceb75ea22753186dae54d967fed894c3dce8
X-Spam-Checker-Version: SpamAssassin 4.0.0
X-Rslight-Site: $2y$10$TSb369tDtNEaUEh2hZCtwuQ03bGP4jIs93N/Dwt2QppdHz2reNty.
Bytes: 4561
Lines: 66
EricP wrote:
>
> It is ok to *try* decoding a length from a token that might be an
> instruction as long as you toss it away when you later find that it wasn't.
> You use the tail of the first instruction to select the start of the second.
> You use the tail of the first pair to select the start of the second pair.
> You use the tail of the first quad to select the start of the second quad.
> For example, if instructions can be 1..4 tokens long
> then the next instruction comes from one of 4 following tokens,
> the next instruction pair comes from one of 7 following instruction pairs,
> the next instruction quad comes from one of 13 following instruction quads.
> Decode0 Decode1 Decode2 Decode3 Decode4 Decode5...
> | | | | | |
> v v v v v v
> Length0->[--------4:1 Select Mux----------][----------...
> | | | | | |
> v v | | | |
> Inst0 Inst1 v v v v
> Length1->[----------7:1 Select Mux---------------------]
> | | | |
> v v v v
> Inst2 Inst3 [----------13:1 Select Mux-----------]
> | | | |
> v v v v
> Inst4 Inst5 Inst6 Inst7
> <---first pair---><--second pair--><--third pair---><---fourth pair--->
> <-----------first quad------------><--------second quad--------------->
Treeifying::
Decode0 Decode1 Decode2 Decode3 Decode4 Decode5...
| | | | | |
| | | Pinst3->[--------4:1 Select Mux-
| | | | | |
| | Pinst2->[--------4:1 Select Mux----------]
| | | | | |
| Pinst1->[--------4:1 Select Mux----------]
| Length1 | | | |
v v v v v v
Length0->[--------4:1 Select Mux----------]
| | | | | |
v v | | | |
Inst0 Inst1 v v v v
Length1->[----------2:1×4 Select Mux----------------]
| | | |
v v v v
Inst2 Inst3 [----------2:1×4 Select Mux-----------]
| | | |
v v v v
Inst4 Inst5 Inst6 Inst7
<---first pair---><--second pair--><--third pair---><---fourth pair--->
<-----------first quad------------><--------second quad--------------->
Where Pinsti is a purported instruction decode which may or may not
be selected as an instruction starting point. This gets rid of the
wide multiplexers at the cost of additional 4:1 multiplexers.
And thanks for taking the time to ASCII-art the figure.