From: Eugene Miya on
In article <et647p$8qk_016(a)s887.apx1.sbo.ma.dialup.rcn.com>,
<jmfbahciv(a)aol.com> wrote:
>In article <45f59384$1(a)darkstar>, eugene(a)cse.ucsc.edu (Eugene Miya) wrote:
>>In article <esp4dj$8qk_002(a)s1016.apx1.sbo.ma.dialup.rcn.com>,
>> <jmfbahciv(a)aol.com> wrote:
>>>In article <1173274591.042195.246470(a)8g2000cwh.googlegroups.com>,
>>> "Quadibloc" <jsavard(a)ecn.ab.ca> wrote:
>>>>Eugene Miya wrote:
>>>>> A step backward John.
>>>>> the S-1 which was supposed to be DEC-10 compatible. Never finished.
>>>>I was waiting for someone to point out that, yes, the perfect computer
>>>>*does* have a 36-bit word, and it is the PDP-10.
>>
>>>I thought your goal was to design a general purpose architecture?
>>>That is the only kind of architecture that can fulfill the
>>>stated goal in the subject header of this thread. One of
>>>the pluses of the PDP-10 architecture is that it was the
>>>perfect computer for anybody.
>>
>>Doubtful.
>
>The key word was "anybody".

I knew the key word was anybody.

>This meant that anybody could
>use the architecture and get something done.

I know you mean that and mean well, but that's not an app perspective.

>It was never meant to be a specialized architecture.

No one said one had to have a specialized architectures. Very few
people see non-Von Neumann machines or analog machines, etc.

>TOPS-10 was described
>as general purpose timesharing. This implies "anybody".

How long do you want to wait for solution?

>>>It is against human nature laws to produce a computer that
>>>is perfect for everybody.
>>Likely true.
>
>There is no likely about it. One man's hell is another man's
>paradise.

While hell and paradise likely have Dantean depths, the analogy is too
simple.

>>>I think this is your tradeoff litmus test.
>>Not bad.
>
>??

Means that I think you are likely in the right directions (maybe a
quadrant) but too binary. Better papers that litmus exist if you insist
on a chemistry analogy. So I reserve judgment on your fuller analogy
on nature's laws.

--
From: Rich Alderson on
jmfbahciv(a)aol.com writes:

> In article <et4hl0$1vlg$1(a)gal.iecc.com>, johnl(a)iecc.com (John L) wrote:

>>> So what was missing in the PDP-10 architecture?

>> Address bits, the same thing that killed every other old architecture.

> Address bits with respect to what? I don't see the problem.
> I'm not a hardware type but a fetch for effective address
> calculations can be 36-bits wide. Can it not?

No, it cannot. The largest offset from an index base (the only way to go
beyond 18 bits of address) is 2^18, and there's no way to get around that.
And there's only one of those per instruction, for most classes of instruction.

> You don't have to change current instructions. You can
> add, or extend, existing instructions to manipulate greater
> than 18-bit addresses.

> For example, refer to the DECsystem-10 Reference Card, part number
> DEC-10XSRCA-B-D. Note that the blue print indicated the KI-10
> only add-ons.

>> The DEC 20 extended addressing was a clever hack, but it was basically
>> 286 style segmented addresses which are a nightmare to program.

> Of course it was a hack. It was a way to provide computing service
> until the next architecture was in production.

> I'm not sure that we ever expected regular users to use it.

Since it is the only way to get a program with large data structures to fit in
more than 256KW of memory, and since large data structures are required for a
number of modern applications, regular users *have* to use it if thye are going
to program those applications on the PDP-10 architecture.

--
Rich Alderson | /"\ ASCII ribbon |
news(a)alderson.users.panix.com | \ / campaign against |
"You get what anybody gets. You get a lifetime." | x HTML mail and |
--Death, of the Endless | / \ postings |
From: Peter Flass on
jmfbahciv(a)aol.com wrote:

> In article <et4hl0$1vlg$1(a)gal.iecc.com>, johnl(a)iecc.com (John L) wrote:
>
>>>So what was missing in the PDP-10 architecture?
>>
>>Address bits, the same thing that killed every other old architecture.
>
>
> Address bits with respect to what? I don't see the problem.
> I'm not a hardware type but a fetch for effective address
> calculations can be 36-bits wide. Can it not?
> You don't have to change current instructions. You can
> add, or extend, existing instructions to manipulate greater
> than 18-bit addresses.

If I'm doing the math right, this is 64 Giga-*Words*, or 256 Gigabytes
assuming you pick 9-bit bytes. Should be enough. If you need more,
change the page-table format (paging makes it a -20, right?) One adress
space could still only map 64GW, but you could have lots of address spaces.

From: krw on
In article <45f6db9c$1(a)darkstar>, eugene(a)cse.ucsc.edu says...
> In article <MPG.206078dd61655fc398a0f7(a)news.individual.net>,
> krw <krw(a)att.bizzzz> wrote:
> >In article <et647p$8qk_016(a)s887.apx1.sbo.ma.dialup.rcn.com>,
> >jmfbahciv(a)aol.com says...
> >> In article <45f59384$1(a)darkstar>, eugene(a)cse.ucsc.edu (Eugene Miya) wrote:
> >> >the S-1 ...
> >> >small address space, fine by me.
> >>
> >> Why does everybody keep assuming that PDP-10s have to be limited
> >> to 18-bit addressing? Isn't it simply a small matter of wiring
> >> to fetch more than 18bits for effective address calculations?
> >
> >You have to encode those bits into the ISA somehow, hopefully in a
> >way that doesn't muck up every program ever written.
>
> Small address space, FYI, was the DEC community's term.
> It didn't matter if it was 8s, 16s, 10/20s.
> And that was OS independent. It could have been the Franz guys
> complaints for LISP.

Ok, I'm more than confused. "OS independent"? PDP8s? 8bit? 16bit?
DEC10/20s?

> Like I keep saying, we have an interesting future.

Sounds like an interesting past too. ;-)

--
Keith
From: jmfbahciv on
In article <MPG.206078dd61655fc398a0f7(a)news.individual.net>,
krw <krw(a)att.bizzzz> wrote:
>In article <et647p$8qk_016(a)s887.apx1.sbo.ma.dialup.rcn.com>,
>jmfbahciv(a)aol.com says...
>> In article <45f59384$1(a)darkstar>, eugene(a)cse.ucsc.edu (Eugene Miya) wrote:
>
><snip>
>
>> >Well as the S-1 was supposed to have 16 "Cray-1 class" CPUs, those guys
>> >decided to have vector registers. So they thought the number crunching
>> >was weak. And a slew of other features. Hey if you want to stay stuck
>> >in a small address space, fine by me.
>>
>> Why does everybody keep assuming that PDP-10s have to be limited
>> to 18-bit addressing? Isn't it simply a small matter of wiring
>> to fetch more than 18bits for effective address calculations?
>
>You have to encode those bits into the ISA somehow, hopefully in a
>way that doesn't muck up every program ever written.

Which bits? The indirect bit?

/BAH