Hello all,
A long time ago I copied most of the pages of the Electronics Today International article "Versatile DRAM Interface for the 6502" by K(eith ?) Howell.
What I forgot to do at the time was also copy the schematic (which was on a different site).
I haven't seen the article on the forum - I can upload it if anyone thinks it's useful - but I would like to study what he did and the schematic would help tremendously.

If anyone can help ?
Cheers, Glenn from France.

Well, I did my searching a bit differently, and I found the schematic.
It is HERE : [url]https://acorn.huininga.nl/pub/mirrors/homepage.ntlworld.com/kryten_droid/circuits/K1001_DRAM_6502.pdf[/url]

The text and schematic are not currently linked. I now have the complete article, and I can upload it if someone wants it.

Well done for finding it! Can I suggest uploading a zip with both the schematic and your scans? Just attach it to a post in this thread.

The article was also (re?) published as a short Tech Tip in the March 1987 issue of Electronics Today International:
https://worldradiohistory.com/UK/Electr ... 987-03.pdf

Here's the relevant pages:


Dave

Also, if anybody needs an easy direct link to it within the magazine, archive.org lets you link to specific pages to come up within their viewer: page 54.

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Curt J. Sampson - github.com/0cjs

Here is the file of the version I have. The schematic is included as was originally published.
Thanks for all of your help.
For the anecdote, ETI in the UK was for about a decade printed in Colchester, Essex - and I used to get it free 'cos my dad was an editor for another mag that was printed at the same place. I still have some of them (mid 70's to early 80's) because of the "Tech Tips" section!

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Because when the schematic is copied, or the paper that it was drawn on gets old and dirty, it is not unambiguous. Is that a . or a speck of dirt? Is that a slightly larger gap between the hand-written digits, or has the . that was once there become invisible? 2k2 is a much more error-tolerant notation.

It's the same reason that we only join lines on a schematic at T-junctions, and the half-loop for crossings that don't join was once used. When the difference between "these two lines join" and "these two lines don't join" is only a dot, it's almost guaranteed that it'll be misread somewhere down the line.

Thank you for saving me the effort of the 2K2 explanation. Also, a bit ironic that someone with vision probems even worse than mine is complaining about that. :-) (I keep a set of 3.5 diopter reading glasses in my toolkit because the 2.0 I normally wear simply won't do for close looks at chip labels or DIP pin connections any more.)

The "join only at T-junctions" idea I'd not heard of, but I throroughly approve. I quite miss the old "jump loop" style I learned in the early '80s, awkward as it is, in part because I've read more than a few schematics of early '80s computers where there were clearly dots missing where lines should join. (The schematics did not make sense otherwise.)

_________________
Curt J. Sampson - github.com/0cjs

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

This has been one of the standard methods (but not the only method) of expressing component values for resistors and capacitors since the 50s, where the "omission by photocopy" of a decimal point was a much larger threat. Here is the Wikipedia article on RKM code, but it's known by several other names/standards depending on the country:

https://en.wikipedia.org/wiki/RKM_code

I do a lot of circuits with current sensing and use a lot of low value sense resistors. Many of those resistors are physically marked using this method as well when they are less than 10 Ohms. Here is a 2.2 Ohm power resistor:

Here are some resistors less than an ohm. The R marks the decimal point position.


If you want to get upset about resistor values, you should reserve your wrath for EIA96 marked resistors. I use a ton of 01C marked resistors, which are obviously 10K, right? (some manufacturers use the "color code" format and would mark the same resistor "103" instead, but using the EIA96 format simultaneously indicates that it is a 1% resistor)

Here is the decoder ring (with actual values listed in RKM format, just for fun):
https://en.wikipedia.org/wiki/Resistor#EIA-96_marking
and if you look carefully, you'll find a resistor marked 34B in a middle photo and that's a 2.21K 1% resistor.