<html>
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
On 16-Feb-16 08:58, Clem Cole wrote:<br>
<blockquote
cite="mid:CAC20D2M7=sFP38JZoAJVyCTrCdUYK7a_=1NvoWNemy=_TtCv4A@mail.gmail.com"
type="cite">
<div dir="ltr"><br>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif">Also it is also interesting to consider that
while the AT&T folks came off of Multics, a number of us
university types that would work on earlier Unix came from
TSS and MTS (one 360/67). In fact, TSS is still the only
system I ever used that lived in the debugger as your
command system - which I always thought was a cool idea. </font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"><br>
</font></div>
</div>
</blockquote>
<font face="arial, helvetica, sans-serif">ITS (MIT PDP-6/10) did
that too. I wasn't a frequent user, but the CLI was DDT.</font><br>
<br>
<blockquote
cite="mid:CAC20D2M7=sFP38JZoAJVyCTrCdUYK7a_=1NvoWNemy=_TtCv4A@mail.gmail.com"
type="cite">
<div dir="ltr"><font face="arial, helvetica, sans-serif">Also, if
you peeked inside a modern processor, you would discover they
are dataflow engines and put together with all of the modern
computer science; but there is about a 5% silicon tax paid for
compatibility. Clearly, my siblings at Intel
believe it's worth tax and the customers seem to keep wanting
it.</font><br>
</div>
</blockquote>
5% is probably fair as as an estimate of silicon area.<br>
<br>
Actually, the real tax is in processor validation. I worked briefly
in that group. It costs more than 5% in manpower to keep making
sure that the compatibility modes (yes, 's') work. The older modes
have lots of quirks and errata that have to be kept bug-compatible
in the face of new implementations.<br>
<br>
The other taxes are more subtle; things like the memory ordering
model and i-stream modification have real performance costs. So
does the limited opcode space, which has resulted in ever more
opcode prefixing. Intel tries to minimize these with ever
increasing cleverness, but they're still there. And probably always
will be.<br>
<br>
Alpha tried to wipe these out with one swell foop, but failed to
grok the software costs. (I did point them out at the time, but the
general belief was that the migration tools would be good enough and
that customers would pay the price for the performance. They
weren't, and they didn't.)<br>
<br>
<br>
</body>
</html>