The trick that the Apple][ did was to map the graphics into the DRAM so that the normal accessing of the graphics data kept the memory refreshed. The 6502 accessed that RAM during one phase of the 2-phase clock and the graphics accessed the RAM during the other phase.

I think you're on to something there. I suspect that is exactly what I did on the 6809 project. A section of the DRAM was dedicated to graphics and was automatically refreshed by the DMA controller.

 

Hello,

Wich number are you looking for?
http://www.americanradiohistory.com/ETI_Magazine.htm

Bertus

Their archive was far from complete last time I looked - Electronics and books may have some, but their server sometimes takes all day just for a directory listing.

 

Hello,

@ian field , the internet archive is even worse:
https://archive.org/details/electronicstoday

Bertus

 

Hello,

Wich number are you looking for?
http://www.americanradiohistory.com/ETI_Magazine.htm

Bertus

I downloaded the DEC 85 issue of the ETI magazine and searched through the whole 1985 index but I couldn't locate the article mentioned.


May be he actually meant the Elektor Mag. ?

I also downloaded the all the available ETI mags. from Oct 1984 to Oct 1986. But there was not a trace of this article.

Allen

 

Cool project. I could not find the original ETI article either. Here is an earlier ETI article with 4164 that may be of help..this one is a little simpler (also see the pages it came from) and also uses 4164 ...and of course the hardware manual. I confess that I am confused about why the entire address space would be mapped to dram, but I don't know.

Hope it helps.

I have glanced through all the articles and websites as pointed. I need more time to digest them properly. I'll post here on the progress after digestion. But my first impression is they are all very helpful.

I confess that I am confused about why the entire address space would be mapped to dram, but I don't know.

I have not yet work out the control logic part of the interfacing. I think I should be able to disable the DRAM for Read/Write functions when I want to use only EPROM and SRAM. So during that period, they can just sit there and do the refreshing.

Allen

 

Hello,

In this radio eletronics manual a dram tester is shown on page 33:
https://archive.org/details/radio_electronics_1991-05
Perhaps this will give some ideas.

Bertus

 

Hello,

@ian field , the internet archive is even worse:
https://archive.org/details/electronicstoday

Bertus

Sometimes a bit slow, but I've found not usually.

If you handle the pages correctly; you can tag the files you want in a download manager.

 

I have glanced through all the articles and websites as pointed. I need more time to digest them properly. I'll post here on the progress after digestion. But my first impression is they are all very helpful.



I have not yet work out the control logic part of the interfacing. I think I should be able to disable the DRAM for Read/Write functions when I want to use only EPROM and SRAM. So during that period, they can just sit there and do the refreshing.

Allen

Yeah I hear ya. I just think that the subject matter is very cool. I still have my KIM-1 and I regret that I did not get into it even more at the time because it seems to me like the 70s and 80s were golden years.

As for that article, I read the other posts and I even channeled my inner @bertus and I can't find it anywhere or any reference to it at all. There is an improved version of a DRAM board in Dec 84 ETI, but it is not by K. Howell. Something is going on with that reference.

 

Hello,

@Raymond Genovese , The ETI dec 1984 can be downloaded here:
http://www.americanradiohistory.com/Archive-Electronics-Today/80s/Electronics-Today-1984-12.pdf
The mentioned article starts at page 31.

Bertus

 

Hello,

@Raymond Genovese , The ETI dec 1984 can be downloaded here:
http://www.americanradiohistory.com/Archive-Electronics-Today/80s/Electronics-Today-1984-12.pdf
The mentioned article starts at page 31.

Bertus

Yup. I was unaware of that site until your post. I too went, reflexively, to archive.org and was also disappointed. That site http://www.americanradiohistory.com/ has a ton of cool old mags - was just browsing the May, 1915 issue of the Electrical Experimenter

 

Yup. I was unaware of that site until your post. I too went, reflexively, to archive.org and was also disappointed. That site http://www.americanradiohistory.com/ has a ton of cool old mags - was just browsing the May, 1915 issue of the Electrical Experimenter

archive.org isn't only electronics - the huge range of content makes your particular interest content look small in comparison.

 

archive.org isn't only electronics - the huge range of content makes your particular interest content look small in comparison.

Agreed. I know that well and am a big proponent of archive.org - see https://www.allaboutcircuits.com/ne...hur-100change-grant-a-100-million-dollar-bet/

 

Yeah I hear ya. I just think that the subject matter is very cool. I still have my KIM-1 and I regret that I did not get into it even more at the time because it seems to me like the 70s and 80s were golden years.

As for that article, I read the other posts and I even channeled my inner @bertus and I can't find it anywhere or any reference to it at all. There is an improved version of a DRAM board in Dec 84 ETI, but it is not by K. Howell. Something is going on with that reference.

I've looked at eBay on the KIM-1 SBC but there are too expensive as the users are selling them as antics. Instead I bought the micro kim kits from Briel's computers.

I have read about the DRAM board on the 1984 ETI DEC mag. Very informative and I'll definitely study it and compare it with my present project. Here's a picture of my micro kim and your KIM-1.



Allen

 

I've looked at eBay on the KIM-1 SBC but there are too expensive as the users are selling them as antics. Instead I bought the micro kim kits from Briel's computers.

I have read about the DRAM board on the 1984 ETI DEC mag. Very informative and I'll definitely study it and compare it with my present project. Here's a picture of my micro kim and your KIM-1.


Allen

Nice! Mine is a Rev B and has the ceramic version of the 6502 - which will be celebrating its 41st sometime in Sep, I guess. The date code stamp on the board is 76 44. Last year, I dug it out of storage cleaned it up and photographed it with the intention of selling it on the bay. After I started looking at it and looking through the First Book of Kim and the manuals and such, I changed my mind

 

I have an Ohio Scientific Inc. C1P single board computer I bought in 1980. It came with 4K of 2114 ram chips and later I max it up to 8K. I never had the chance to add the IO/RAM extension board cause it was too expensive for me at that time.

I later bought a used C1P that came with a nice wooden case very cheaply. I did a lot of mods on the first C1P by changing the monitor ROM to CEGMON that was used in UK101. I also changed the video mapping from 32x32 to 64x24 (Not sure if I added a pair of 2114 to the video RAM or not).

I read PEEK65 and Micro magazines that has a section dedicated to the OSI machines.


allen

 

Absf: Have you considered to map some of the memory areas to an external device i.e I/O, or graphics or sound? If you need to combine those peripherals, you may need a CPLD or a small FPGA to do so. Otherwise, you can use a lot of logic gates but it will become a tedious work afterwards.

 

No, my interest is only to make the DRAM work. IO or graphics would be another project when this one is working.

My only problem now is how to enter program into the memories when the whole memory is occupied by the DRAM. I need at least some area from $F800 to $FFFF for the monitor program and some SRAM on the lower memory areas for the scratchpad and variables for my program. In 6502, $0000 to $00FF are VIP area called "zero page area" for program to use direct and indirect addressing modes.

I cannot do everything in one project. Easier to split them into sections so I can do a piece at a time.

the IO and and graphics and UART should be on the 3rd section. May be the DRAM interfacing part using CPLD/VHDL would be second.

Allen

 

In 6502, $0000 to $00FF are VIP area called "zero page area" for program to use direct and indirect addressing modes.

The 6502 also needs memory for the stack. This is in page 1 ($0100 -$01FF) for a completely decoded memory. In a minimal system (not recommended) the stack can be overlayed with page zero.

 

Oh, yes. How could I forget the stack. So I need at least 1KB from $000 to $3FF. A 6116 would do it.

Allen