Memory current demand

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Tomswork
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Memory current demand

Post by Tomswork » Fri Jul 17, 2020 11:45 pm

Do the 41256 k dram in dip packages really use 5v at 300mw averages and the st is full of them

:fan:

This is why the power supply in my ste loves exxos simms

Tom

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PaulJ
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Re: Memory current demand

Post by PaulJ » Sat Jul 18, 2020 12:15 am

Hmm, 1 meg machine, 32 memory devices, 32 x .3 = 9.6 amps.. Don't think a ST power supply will do that... not to mention current draw is dependent on what's going on with the memory. Also memory chips used on sim's are also used on dedicated main boards. A modern dynamic memory device generally uses less power than older devices..

Tomswork
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Re: Memory current demand

Post by Tomswork » Sat Jul 18, 2020 12:45 am

This is what I was wondering on the sizing of the psu.
Screenshot_20200717-164308_Drive.jpg
Screenshot_20200717-164308_Drive.jpg (172.47 KiB) Viewed 711 times
The psu close to full load or it's under power all the time

Tom

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PaulJ
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Re: Memory current demand

Post by PaulJ » Sat Jul 18, 2020 1:13 am

Dynamic memory current draw is very dependent on what its doing. Here's the current section of a toshiba device. No where near what yours states. Most Atari St's, Mega's and the H4 draw 1.5 - 1.9 amps in my experience.
dm.jpg
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Tomswork
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Re: Memory current demand

Post by Tomswork » Sat Jul 18, 2020 1:54 am

That's what I figured so going from 8 per simm to 2 saves alot on the psu.

Tom

cmorley
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Re: Memory current demand

Post by cmorley » Sat Jul 18, 2020 8:57 am

PaulJ wrote:
Sat Jul 18, 2020 12:15 am
Hmm, 1 meg machine, 32 memory devices, 32 x .3 = 9.6 amps..
You've got an arithmetic error here...

OP was mW not mA

300mW @ 5v = 60mA.

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PaulJ
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Re: Memory current demand

Post by PaulJ » Sat Jul 18, 2020 4:27 pm

cmorley wrote:
Sat Jul 18, 2020 8:57 am
PaulJ wrote:
Sat Jul 18, 2020 12:15 am
Hmm, 1 meg machine, 32 memory devices, 32 x .3 = 9.6 amps..
You've got an arithmetic error here...

OP was mW not mA

300mW @ 5v = 60mA.
Hmm, doesn't look like a math error... looks like some dumb ass plugged in a mw value instead of a intended ma value.. In my defense it was late, and the topic was "current" demand so I assumed a current value... even though it appeared as a ridiculously high value.. Never the less my point remains... The dynamic memory isn't eating the power supply and simm's use the same memory chips that are soldered on main boards of the era. Matter of fact when I was looking for some 1 meg x 1 dynamic memory chips for my mega I ended up getting a couple of simms that used the exact chips I needed. Guess I'll have to work on my reading accuracy a little. :chairsmack:

tzok
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Re: Memory current demand

Post by tzok » Sat Jul 18, 2020 5:17 pm

...it is a 2.3 A max for a 1 MB machine.

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