[Info-vax] AlphaServer 1200 memory question

[H Vlems]

On 24 jan, 12:24, John Wallace <johnwalla... at yahoo.co.uk> wrote:
> On Jan 23, 12:09 pm, H Vlems <hvl... at freenet.de> wrote:
>
>
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> > One AlphaServer 1200 is fitted with 16 memory boards, 128MB per board.
> > The system has 2 GB available. The memory is fitted in pairs and you
> > can't mix sizes. I ordered additional boards for a few other 1200's
> > and I decided to check all my 1200's and Digital Server 5305's for the
> > brand and the specifications of the memory boards.
> > The system with 2 GB had 1 memory board with a 66 MHz (PC66) sspec
> > inside, it was matched with a 100 MHz board of the same brand and size
> > on the other riser card. All memory is Micron MT18LSDT1672AG-10EC7
> > except one which is MT18LSDT1672AG-662B4.
> > The question is: does the single PC66 board slow down the entire
> > memory configuration, or was I lucky and the PC66 board just happens
> > to run at 100 MHz without generating memory errors?
>
> > Side question: did Digital ever publish memory specifications for its
> > Alpha's? I know that the Micron memory works, as well as NEC and SEC
> > boards but I'd like to know how to select SDRAM from a manufacturer's
> > catalogue by specification.
>
> > Hans
>
> That kind of info would be somewhere in the specs for the Alpha chips
> that came through Digital Semiconductor with the intention of sale
> into the merchant semiconductor and motherboard market. You'd probably
> have to dig through lots of manuals to find the info though. There
> should be specs for EV4 with 2107x chipset and EV5 with 2117x chipset,
> but probably not the EV5 chipset used in the PWS family. The Digital
> Semiconductor side of the business had gone by the time EV6 came out,
> so you'd need a different route for EV6 memory specs.
>
> If your interest is EV4/EV5 era, you might find a "Motherboard Design
> Guide" or two from Digital Semiconductor which should have the kind of
> info you're looking for in a somewhat more accessible form. They do
> exist but a quick look in the usual search engine didn't find any.
>
> Good luck
> John- Tekst uit oorspronkelijk bericht niet weergeven -
>
> - Tekst uit oorspronkelijk bericht weergeven -

My interest is vey focused on the AlphaServer 1200 (and the Digital
Server 5305).
I found an article in Dig. Tech. J. vol.8 nr. 4 page 48 which
describes the design and architecture of the
AlphaServer 4100 (and a few interesting notes regarding the 4000).
Assuming that a 1200 is basically half a 4100 the paper is very
useful.
The author, Glenn Herdeg, explains in clear language the design goals
and the way these were met.
For the memory subsystem this means that it runs at 66 MHz. So
anything goes as long as it can handle 66 MHz bus speeds.
The latency is no problem because CL 2 for PC66 memory translates to
7.8 ns, faster  memory has reduced latency times for CL 2 memory
(at 100 MHz CL 2 reduces to 5.5 ns). This is why PC66 and PC100 boards
may be used together in the same slots on both riser boards: the
system
can just keep up with PC66 memory so faster modules have an easy job.
The paper states that the 4100 can handle 512 MB SDRAM boards. I'm
going to try this on a 1200, if it works the memory can go up to 8 GB.
Hans