Re: Question about DRAM IC's

Hello Roger.

> > I'm not sure I understand what you mean about 'The problem is that two lots > of 512 cycles, do not activate the extra address line, that a '1024' cycle > refresh implies...'. >

Your first problem is that you've cross-posted to a slew of groups. I have very little desire to reply to some fool who feels they need to do that.

But not only do you overly cross-post, but you lack comprehension.

Inside the dynamic ram is an array of rows and columns. The refresh is to activate each location in turn, because dynamic memory is not static. It needs to be access in order to keep it's content. Since it's an array, you don't need to go through the full address space, just whatever is specified, the row or column.

To use a simple example, say it's a really small RAM, 8 columns by 7 rows, ie 56 address locations. You have to refresh all those columns each time for a full refresh to happen. If you only had a counter with 7 bits output, one of those columns would never see a refresh, so a significant amount of the memory space would never be refreshed.

So you get one of those new DRAMs with twice as much space, having 9 columns by 7 rows, all of 63 bits. Your old refresh circuit will no longer be good enough, because it has 8 outputs, but you now need 9 bits.

That's what they are all trying to tell you as you spew this thread over a bunch of newsgroups.

The details are specific to the DRAM. Some may require column refresh, some row refresh, and the arrangement of the array will vary. You have to track down the details and then match that.

Michael

Reply to
Michael Black
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Pardon ?

Cross-posting to just *3 relevant groups* is the recommended practice. Far better than mutli-posting.

Graham

Reply to
Eeyore

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The problem may not relate to refresh...

Think about where each of the Apple's raw address bits are going. Remember that some address bits are used as Row bits and some are used as Column bits.

The host system (Apple IIe?) controls how the bits are multiplexed... you can't just put chips with a different number of Row & Column bits than the system was designed for and expect it to work. (hint: Lost Address Bits)

Dennis

Reply to
Barbarian

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