Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!haven!uvaarpa!virginia!uvacs!mac
From: mac@uvacs.cs.Virginia.EDU (Alex Colvin)
Newsgroups: comp.arch
Subject: Re: String lengths
Message-ID: <2980@uvacs.cs.Virginia.EDU>
Date: 15 Feb 89 16:46:48 GMT
References: <8882@alice.UUCP> <22036@ism780c.isc.com> <1185@houxs.ATT.COM>
Organization: University of Virginia
Lines: 18

In article <1185@houxs.ATT.COM>, beyer@houxs.ATT.COM (J.BEYER) writes:
> In article <22036@ism780c.isc.com>, news@ism780c.isc.com (News system) writes:
> > The 7090 provided no instructions for accessing individual characters.  The

> As I recall, the GE635 and 645 did have ways to address either 6 or 9 bit

It did.  Unfortunately, there were several incompatible ways,
the new (EIS string, all memory-memory),
the old (tally words, all memory to register)
and the incredibly old (fixed character/byte, memory-register).

I've heard of a cute way to implement character addressing on a 7090 using
one half register for the word address, another half for character offset,
and XECs to choose a load/store, with an XED chain to wrap the character
count into the word address.  Almost microcode (cf Clipper macrocode?)

			Alex Colvin
			old DTSS programmer