[GTALUG] New Deaktop PC -- To Run debian Linux - PCPartPicker Recipe;

[o1bigtenor]

On Wed, Mar 28, 2018 at 5:35 PM, D. Hugh Redelmeier via talk <
talk at gtalug.org> wrote:

> | From: o1bigtenor via talk <talk at gtalug.org>
>
> | Not the OP but  - - - - one issue I'm seeing - - - my main system (its
> over
> | 6 years old)
> | has 8 slots for ram. Almost none of the newer mobos have that many.
> | (Just one point for where newer isn't always 'better' (whatever that
> means!
> | - - grin).)
>
> My Sun 3/60 has 24 slots.  But the largest memory module that it will
> accept is 1MiB (note: not 1GiB).  So more isn't always better :-)
>
> As memory systems get faster, fan-out and signal path length matter
> more.  So 4 is apparently the limit for "unbuffered" memory on one PC
> memory bus these days.
>
> If you have multiple processors on a motherboard, they probably have a
> separate bus for each processor so you get 4 slots per processor.
>
> If you have a big server, you use buffered memory (probably with ECC too)
> and can have lots* of RAM sockets.  With buffering, you lose speed but
> gain fan-out.
>
> Complicating this is the market segmentation games that Intel is
> playing.  Apparently you pay a lot for a Xeon processor that has enough
> address lines.  AMD Epyc is smashing those limits so interesting
> things might happen.
>
> This supports 16 LRDIMM DDR4 modules, each could be 32GiB (I think).
> 2TiB in total (that's 16 x 128 GiB, so I'm missing something).
> <http://b2b.gigabyte.com/Server-Motherboard/MZ31-AR0-rev-10>
>
> In the good old days, bulk dynamic RAM chips were 1-bit wide so if
> your bus was 32-bits wide, you could drive 32 chips with no fan-out on
> the data lines.  Now RAM chips are typically 8-bits wide, modules are
> 64-bit wide, and busses are 64-bit wide, so fan-out is a larger
> problem.
>
> * "lots" is a technical term meaning more than four, but I don't know
> how many
>

OK - - - if I had been referring to server boards I wouldn't have commented
but as
I was talking about desktops - - - well - - - my point still stands. IIRC
when I last
looked (a couple months now) all the desktop boards were topping out at 4
ram slots.

Dee
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