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| [6 earlier articles] |
| Re: C arithmetic, was Software proofs, was Are there different gah4@u.washington.edu (gah4) (2023-02-09) |
| Re: C arithmetic, was Software proofs, was Are there different gah4@u.washington.edu (gah4) (2023-02-09) |
| Re: C arithmetic, was Software proofs, was Are there different DrDiettrich1@netscape.net (Hans-Peter Diettrich) (2023-02-10) |
| Re: C arithmetic, was Software proofs, was Are there different gah4@u.washington.edu (gah4) (2023-02-10) |
| Re: C arithmetic, was Software proofs, was Are there different gah4@u.washington.edu (gah4) (2023-02-11) |
| Re: C arithmetic, was Software proofs, was Are there different anton@mips.complang.tuwien.ac.at (2023-02-11) |
| Re: C arithmetic, was Software proofs, was Are there different drb@ihatespam.msu.edu (2023-02-12) |
| From: | drb@ihatespam.msu.edu (Dennis Boone) |
| Newsgroups: | comp.compilers |
| Date: | Sun, 12 Feb 2023 04:37:07 +0000 |
| Organization: | Compilers Central |
| References: | 23-01-092 23-02-003 23-02-019 23-02-025 23-02-026 23-02-029 23-02-032 23-02-035 23-02-039 |
| Injection-Info: | gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="61234"; mail-complaints-to="abuse@iecc.com" |
| Keywords: | architecture, history, comment |
| Posted-Date: | 12 Feb 2023 12:18:23 EST |
> The three index registers were 1,2, and 4, and if you specified more
> than one, it OR'ed them together and subtracted the result, which was
> really strange. There were a lot of other machines with index registers
> but none I know of that subtracted or OR'ed. I have also been unable to
> tell whether the OR'ing was deliberate or just a result of minimizing
> the number of tubes that they then documented.
Not having to have the circuitry to make sure multiple registers
were never gated onto the internal bus seems like a likely reason.
But one _could_ also conceivably use multiple index registers for
multiple dimensions, with careful allocation.
De
[As I said, I've found lots of guesses but no documents. Multiple
dimensions only work if each dimension is a power of two which,
considering the 704's tiny memory, seems unlikely. My guess is the
same as yours, fewer tubes, but it's just a guess. -John]
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