Every time I look at the AIIE 80COL card in my drawer, I wonder if there is an idea to make use of this card that I never use. Actually, I have about 8 of these cards... My friend Bill Martens said he had more than 10, and I was relieved to hear that other friends also had extra.
I don't know if I saw it somewhere or if it was just my imagination, but I thought it would be a good idea to attach a daughter card to it and use it as a RAM card. I thought this would be a great project for people like me... they have too much of this card to use again.
Of course, Apple II geeks loves the 80COL card themselves can ignore my project. I just thought of a way to make use of the 80COL card. I wanted to explain this carefully.
This is not a project to destroy an 80COL card, but a project to install a RAM daughter card using 80COL IC sockets. Therefore, the 80COL card can be easily restored.
Recently, 80COL has been supported in Mark Aikens's AII VGA projects. You can get this functionality without an 80COL card. In fact, if you have AII VGA, you can do what you want with 80COL. *We are also selling AII VGA MINI.
Daughter card concept
I started by writing and reverse engineering a schematic for the 80COL card. Naturally, both AIIE 80COL (820-0066-A) and AIIE 80COL/64K MEMORY EXPANSION (820-0067-D) have the necessary similarities, so I thought this project had a high chance of success.
A0 to A7, D0 to D7, RAS, CAS, and R/W80 can be taken out from the IC socket, and RAM control seems to be fine.
However, we did not have the following points in common, but I thought we could resolve them.
*AIIE 80COL/64K MEMORY EXPANSION (820-0067-D) was already reverse engineered by my friend Brad Bell, which was very helpful.
Differences and predictions
I'll give the conclusion first, this card mod only requires one jumper (50-pin AN3 and 55-pin FRCTXT on the card edge), and the rest can be left as is. So, if you want to return to the original 80COL card, you can restore the original by returning the three chips and cutting the added jumper.
My thoughts are on the following three points:
1, In the case of an 80COL card, the EN80 signal is input directly to the C/S of LS245, but in the case of a 64K MEMORY card, it passes through LS14 four times before being input to the C/S of LS245.
I asked Brad Bell (aka, BTB), who seems to be knowledgeable about this, and he said he doesn't know exactly why, but the loan card he wants to have doesn't have an LS245, and like the 80COL card, the EN80 signal doesn't work. It turned out that it was being input directly to the C/S of LS245. Brad Bell's guess was that they were delaying the EN80 signal for some reason, which I thought made sense. I actually found that when I created a card without the 74LS245, it worked without any problems.
2, 80COL card, D0 to D7 and pin 4 of LS75 of UA1 are pulled up with +5V. Although it is not necessary for memory cards, this pull-up has a 3.3K 10-pin resistor array between +5V, but I thought that there would be no effect even if it was not removed. I actually checked the operation with it installed as is, and found that there were no problems even after more than 200 RAM tests. I decided that it was okay to leave it as is.
3, 64K MEMORY card, the 50-pin AN3 and the 55-pin FRCTXT are connected on the PCB from the card edge. This silkscreen is written as AX1 and is a jumper pad, and the premise is that the user can also cut it later.
In the case of the 80COL card, there is only a contact pad without router, but nothing is wired to it. You'll need to use some thin copper wire to make a jumper, but it's not a big problem. This is the only place where you can modify the card. I think you can solder without failure by masking tape the solder area by leaving about 2mm(0.1") of solder so that the solder doesn't flow into the gold plating.
This jumper is actually required to generate "double heres mode". If we are using AII VGA, we will be generating video directly from the CPU, so this jumper is not needed (video output is not affected). However, when I tried it with the composite RCA video output, I found that it was not possible to generate images correctly in "double hears mode", as shown in the pictures below.
We choose “Airheart” as a good example of double hears mode to test with appropriate software. The results were very interesting as you can see in the pictures above.
Instructions
Here is the download link.
Sales destination
This RAM Hijacker DIY kit sells for 13USD in our store,
The shipping cost is a little high since it will be sent to you from Japan, but please buy it together with other products or share the shipping fee with your friend...
Expected development after this
It's doing pretty well for a 64KB RAM card. It is a good card that functions just like the genuine product and has no errors. Most software works with 128KB, so I have no complaints about this capacity. I also have 8MB IIe RAM cards, but the way I use them doesn't benefit from more than 128K. Many geeks will feel that way.
But if I have another chance after this, I would like to design RAM card with the capacity increased to about 4MB. That will be another story. Thank you for reading to the end. Hope you have fun hacking your Apple II!