🚀 go-pugleaf

chuckst@microsoft.com (Chuck Strouss) writes:

>In article <1gske7INNgje@coli-gate.coli.uni-sb.de> chbl@sbustd.rz.uni-sb.de (Christian Blum) writes:
>>
>>No way this will work. The refresh rate is set to 18.2 per second; since
>>there are 512 rows to refresh, this means every bit in your computer's
>>DRAM is refreshed every 20 seconds! There are DRAMS that survive 15ms
>>without being refreshed, but a 70ns DRAM can't take it. Try about 10ms
>>......

>It is surprising how long some DRAMs can go without refresh.  For
>production systems, you must believe the manufacturers worst-case
>specs, but DRAMs rarely need to be refreshed that often.

>A while back, I was working on the software for a computer system that
>did its DRAM refresh with a software interrupt -- it only took about
>5% of the CPU time.  At first, we had a bug in our refresh code, but
>the system was still working remarkably well.  Tracing down another bug
>revealed that we weren't refreshing at all, except for the natural
>refreshing that came from the execution of code.

>Once we got the refresh working, we decided to determine exactly
>how slow we could refresh and still have the system work.  We made
>sure that the CPU was executing in a tight loop the rest of the time,
>so that normal execution wasn't refreshing.

>Turns out the particular DRAMs we were using, at the temperatures
>we were running, held their contents just fine with a 1-2 second
>refresh rate.  They started failing a bit at 5 sec, and were
>still 80% correct after 15 sec.

>We expanded our experiments a bit, and tried DRAMs from different
>manufacturers, and also tried different temperatures.  There
>were remarkable differences with both parameters.  We ended up
>taking the full 5% CPU hit requirred to meet the manufacturers'
>specs, which I think is a good decision for anybody who is tempted
>to play around with refresh rates.

Ther are couple of files at simtel-20 (or its mirrors) under sysutl
called qram.zip and fastram.zip (or maybe .arc) that let you play
with the DRAM refresh rate and results in 5% to 10% CUP speed increase.

I managed to increse my CPU speed from 16.2Mhz to 17.33Mhz (checked it
out using Landmark SPEED200). Interesting enough the video speeds up to
and i can see inprovement when Windows is redrawing the screen.

-- 
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Tooraj Enayati     Melbourne     Australia     tooraj@daneel.rdt.monash.edu.au
Monash University       Robotic and Digital Technology       (Graduate/Alumni)
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