[rescue] Enterpise E4K questions...

[Skeezics Boondoggle]

On Thu, 17 Feb 2005, "Gutschner, Marc" wrote:

> > On Wed, 16 Feb 2005, Phil Stracchino wrote:
> >
> [... Phil and Chris pointing out architectural details ...]
> > The US-II Enterprise machines are architecturally more like the
> > sun4d/XDbus machines - you don't have the memory locality issues that the
> > newer SunFires have, so there's a constant latency between any CPU and any
> > memory bank, regardless of their physical configuration.
> 
> Ok, so this brings up another question. I remember some short discussion
> a few weeks (or months?) ago about the mid-range Enterprise systems.
> IIRC it was about different CPU speeds in one system. So, can I add -
> for example - boards with 336MHz CPUs to the system without "frying" the
> existing 250MHz ones? I know that the 400MHz boards are a completely
> different beast and that I need a different clock board to use them in
> an E4k...

In general, it's best to match speeds.  You can, however, mix and match 
boards, but the machine will be goverened by a) the clock board, and b) 
the slowest component in the box.

That is, with an 83Mhz clock board, you can install 100Mhz boards but the 
machine will still run the bus at 83Mhz.  If you upgrade the clock board 
to 100Mhz, you have to make sure all the CPU/MEM _and_ I/O boards are 
100Mhz capable to run at full speed.

CPU modules can be mixed & matched too, but the machine will clock them
all down to match the slowest one.  I think in past discussion here 
someone sayd that 'prtdiag' will report their true speeds, but they'll all 
be running at the same speed.  Similarly, the smallest L2 cache will 
determine how much cache is used on each module - mix a 1MB with some 4MB 
modules, and you'll waste the extra cache (but it will run).

> > However, you *do* want to populate the memory banks in the
> > sequence Sun recommends in order to get the best interleaving possible.
> 
> The machine currently has the 1GB stretched across all 4 banks, so this
> gives me the maximum interleave for this configuration, I guess...

If you boot Solaris and run 'prtdiag -v', or if you get into the nifty 
diag menu at the PROM (I'm spacing out the special key sequence to access 
that, at the moment...) you can see lots of interesting stuff.

> > Generally you fill up the CPU slot 0's first, and the memory bank 0's
> > first, but the rules are laid out in the Ultra Enterprise Systems Manual:
> 
> What I'm still wondering is: Do I have to populate the DIMM slots
> symmetrically? From the documentation I get the impression that the only
> constraint is that each Bank 0 has to be populated with some memory. Is this
> correct? And must all Bank 0 have to have the same density?

I think the Sun guide says to start with the highest density DIMMs (128MB
in the docs - but 256MB parts work too?) in the low bank, then work your
way down to the medium (32MB) and low (8MB) parts.  I don't know if you'll 
get interleaving across boards if board 0/bank 0 has 128MB parts, and 
board 1/bank 0 has 32MB parts - my guess is that it won't.  However, the 
PROM seems to be able to figure out "partial" interleaving, and will try 
to optimize across banks whenever possible...

-- Chris