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Re: RAM for AS200



With regards to your message at 12:15 PM 09-09-98 -0400, Stephen J. Gaudet.
Where you stated:
>Hello Robb
>
>>> One word of caution, when installing ram into a Digital AS 200 or even XL
>>> series. The problem we've seen is they can not run 60ns ram, must use 70ns
>>> or have the memory vendor slow down 60ns to 70ns.
>>  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>
>>How do they do that?
>
>Look on the side of your simms.  There are small jumpers (most have 4)that
>will clock the simms down.
>
OK, sorry, but I HAD to rise to this one Steve.
These jumpers do NOT slow down the RAM.
What they do is feed some info to the computer. In the case of some of the
older Alphas they actually look to these settings to get info on what speed
RAM is supposedly on the SIMMs. Depending on this info they treat it as 60,
70, or 80, and adjust some system timings to suit.
 These are called PD jumpers, and if you want to read all about it then get
teh spec sheets from JEDEC. "JEDEC". Jedec is the Joint Electronic Devices
Engineering Council and they set standards and compliance specs for
component packaging, inclduing SIMMs and DIMMs.
 In other words, depending on the settings of these jumpers, the computer
talks to it on writes at differing speeds. I doesn't actually change the
real data rate, but instead introduces wait states between small blocks of
data transferred to the components.


Best regards,

  Maurice W. Hilarius                   Telephone: 01-403-414-9319
  Hard Data Ltd.                      **FAX:       01-403-456-1510
  11060 - 166 Avenue                    email:maurice@harddata.com
  Edmonton, AB, Canada  - T5X 1Y3       http://www.harddata.com
  



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