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Re: Do I need 64Bit if RAM is more than 4 GB?

On Wed, 8 Sep 2004, Lennart Sorensen wrote:

On Wed, Sep 08, 2004 at 04:09:59PM -0500, Ron Johnson wrote:
"Part IV: IBM RS/6000 POWER chips (1990). . . ."
"Thirty two 32-bit registers were defined for the POWER1 integer
unit, which also included certain string operations, as well as
all load/store operations."
Blah blah blah POWER2
"It was superceded by the POWER3 (Early 1998), with eight functional
units (two FPU, three integer (two single cycle, one multicycle),
two load/store, and branch unit), but capable of operating at much
higher clock speeds. In addition, a 64 bit version, the PowerPC
A35 (Apache), was designed for the AS/400 E series"

So, the first 64 bit POWER chips arrived 8 years after the 32
bit versions.

1998 seems like a fairly resonable time to start getting into 64bit.  I
guess it does indicate the power wasn't designed as 64bit to begin with,
but seems to have been designed well enough that extending it later was
reasonable to do.

Ehm. There is no 64-bit version of the POWER ISA, it was extended/fixed/replaced by the PowerPC ISA which was designed with 32 and 64 bit implementations to begin with (I think). POWER3 is a ppc64 implementation selling under the POWER brand, not a 64-bit POWER implementation.

Before the POWER3 (and other ppc64 implementations), the SMP rs6000 machines where 32-bit ppcs and had address limitations which meant that the maximum ammount of memory supported was around 3-3.5 gigs. This is in place even for the ppc smp sp2 node called "silver", which I happen to run a couple of for ftp.se.debian.org. These were the high-end computational resources that were replaced by the POWER3, and couldn't handle more that 4 gigs of ram.

The IBM sales manuals are around and pretty good at telling you exactly what hardware combinations are/were supported, I think you'll notice that the support for more than 4GB came at the launch of the POWER3 (or the RS64(?) chip, another ppc64 implementation used by ibm for the commercial computing segment rather than technical computing).

Well, sparc64 has been around an awful long time. Adding PAE-like hacks seems

Since 1995.

There were largish SMP SPARC32 boxen for many years before the
SPARC64 came into existence.  I can't find any references on the
web, but some of those big boxen had to have more than 4GB RAM.

I wonder how much 4GB ram would have cost in 1995 or even 1998.  I
remember getting 16M for a 486 for $600 in 1992.  I think it was 1996
when I got 128M for about the same amount.  The price lists I found once
for Decstation 5000 boxes had ram listed at around $50000 for 128M in

Even in 1995 4GB would have been a rather expensive amount of ram even
for a high end sparc or power machine.

Well, instead of searching for prices, go find an old manual of the largest sun sparc32 smp? The one I can think of right now is the ss1000, were there any bigger ones? Before the ultrasparc days that is.

/Mattias Wadenstein

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