Building a NeoRam Ram expansion memory cartridge for the C64 computer

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banman
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Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by banman »

Hi Zippy Zapp,


I thought I'd post some personal observations on building a NeoRam Ram expansion memory cartridge for the C64 computer.

https://www.hackup.net/2019/04/the-neoram-remix/

Essentially it is one of these

http://www.cbmhardware.de/show.php?r=1&id=9/Neoram

Which is a GeoRAm...


http://www.cbmhardware.de/show.php?r=1&id=4


Please let let me know if I have made any errors on this.

The the Neoram-remix PCB's are available for order at PCBWAY.com (this is not a paid endorsement). The PCB being under 100x 100 mm means that one can order the bare PCB's for 5$ USD not including shipping, at least I did this some time ago.. Unfortunately with the World in it's current state of flux things may have changed.

Zippy Zapp you mentioned ways to test the ram functionality of the NeoRam. Recently eslapion posted a link to a useful site. I must say I never came across this in my wanderings. It seems good though and I must test it out time permitting.

https://gglabs.us/node/2065




I used these 2 applications...

A program called "ramexp-check". It's actually German so I had to translate the instructions into English. I think the german name is ramexp erkennung if you are looking for it on the internet.
ramexp erkennung NeoRAM cartridge software.zip
(172.69 KiB) Downloaded 28 times
Here's the English instructions.



load the program "ramexp-check" with, 8.1.
Type in new and confirm with return.
then load and run the basic program with, 8.


10 sys49152
20 printpeek (52992)
30 printpeek (52993)
40 printpeek (52994)
50 printpeek (52995)
60 printpeek (52996)
70 printpeek (52997)

order of peek output
----------------------------
1 = georam identifier is always 1
2 = georam ram size. 00.03.07, 15.31.63
3 = re-identifier is always 2
4 = reu ram size. 00.01.03.07.15.15
5 = scpu identifier is always 3
6 = scpu ram size 00.01

info on ram size
-----------------
00 = no ramexp or no ram available
01 = 0128 kb ram and for the scpu = 1024 kb
03 = 0256 kb ram
07 = 0512 kb ram
15 = 1024 kb ram
31 = 2048 kb ram
63 = 4096 kb ram


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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by banman »

The second program I used is NeoRam Test.

http://www.cbmhardware.de/dlmanager/index.php?id=444


With these 2 applications I was able to determine if the the the memory modules were functioning correctly (more on this later) and if the wiring to the logic IC's and the jumper settings were properly installed/ configured.



NeoRam test is good to use. It will test the RAM and let you know which UC chip is under investigation as well as if there is a fault. It will also show how much RAM the cartridge it is configured for. If there is a RAM fault it will return an error for that particular IC which was very handy in my case. Some of the boards I had soldered had damaged memory IC's.
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by banman »

Here ia a web site with some links to software the utilizes C64 memory expansion cartridges.


http://members.optusnet.com.au/spacetax ... -TOOLS.htm
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by eslapion »

Concerning your logic chips:
- 74S138 is okay but will consume lots of power; a good replacement is 74LS138; the ideal replacement is 74HCT138
- 74174 is okay but will consume lots of power; a good replacement is 74LS174; the ideal replacement is 74HCT174

Concerning your PCB:
- Not gold plated edge connector results in: https://www.tsb.space/bl0g/ultimate64-c ... t-problem/

If you purchased any of these chips on eBay or Amazon, you can be assured some of them will be 74HC chips which are not RoHS compliant and made before 2004 that were rebranded in China.

Chips that are not lead free (made before 2004) are now illegal for sale but Chinese companies get them at very low cost and changes the branding to sell them back where ever they can. They essentially get chips that are worthless and changes whats on them to make money out of worthless goods.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by banman »

Hi eslapion,

Thank you very much for all the useful information and especially on using more suitable logic chips. :D

Yes, the logic chips I'm using will definately be lead carrying. These were chips that came from the electronics store that was closing. The OEM 74174 chip dates from 1977 the 74s138 dates from 1988 and the Philips 74HCT273 dates from 1989 I believe.

The PCB's are all HASL (for hot air (solder) leveling) possibly lead based. If you look at these attached pictures you will notice on some of the boards I received, the manufacturer attempted to grind a 45 deg "V" wedge at the connector edge on one side then promptly forgot to run it down the full length.
Leaving a square edge at the other. How rude! :shock:
IMG_20210906_124746.jpg
IMG_20210906_125316.jpg
I got 5 x PCB's for my 5$ USD not including shipping. The first 2 builds went of fantastically, no real dramas. I was very surprised. I can handle the constructed units very safely in the hand. Static charges don't seem to bother these in any way.


Another point I will make is the memory IC's.


The other 3 PCB's had major issues regarding the reliability of the RAM IC's. I am not sure if the way I soldered the ICs on the PCB were to blame or it was the very CHEAP memory IC's I purchased were the problem. I will say it's a bit of both.




I used these brand of IC's because the datasheet suggested an extremely low standby current draw. Making these very nice for the backup memory versions.

I ended up opting for Cypress branded 512K x8 CMOS static RAM modules. The data sheet had them down at a slightly lower operating current and they were cheaper.

https://www.cypress.com/file/43851/download


https://www.aliexpress.com/premium/cy62 ... 8ell-55sxi



I found soldering the memory chips to the PCB easier than I expected considering their pin width.

Now, I can't in any way vouch for the origin of these memory IC's. I don't have any genuine branded memory IC's of the same type to compare along side. Knowing now from plenty of experience at detecting knockoff (fake) IC's I would say yes, these are 90% not genuine IC's.


I give this as one of many examples...


viewtopic.php?f=27&t=14055

The markings on these 6522 VIA chips were so convincing that only when I reviewed the pictures of them side by side with genuine unmodified ones that there were definite inconsistencies. The chips I think are genuine,however the original markings have been ground down and physically etched ones put in there place. Laser I am thinking!
All that effort for $1.50 AUD a piece shipped!

I challenge you to look closely at these photos (click on them they come up as hi_res) and give your opinions.
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by eslapion »

banman wrote: Mon Sep 06, 2021 4:40 amI challenge you to look closely at these photos ... and give your opinions.
Challenge accepted.

Verdict:
You are a brave and patient man!

Soldering surface mount components with a relatively high pin density is easy because you can use drag soldering and just slide a drop of solder across the pins and the soldering occurs all by itself. Solder through hole is also easy as you apply solder to pins one at a time.

You, on the other hand, have chosen the difficult path of SOIC and were successful at it. This is the type of surface mount ICs I absolutely hate to solder because you can't just drag a drop of solder across the pins as they are too far apart.

My hat off to you!

There seems to be a short between pins 10 and 11 of UC2. Also another one between pins 23-24.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by banman »

Hi esplapion,

Thank you, I appreciate the kind words. It means a lot. :D


I couldn't solder the legs by drag soldering as you say. I used a conical tip soldering iron and soldered each pin individually. It took a while. Probably because it is a hobby I enjoyed the challenge. I would definitely say it wouldn't be fun if one was making a living doing it this way.
I liked the project because it crossed over from through the hole components to surface mounted parts. It gave me the opportunity to increase my very average soldering skills.

Gee, you've got keen eyes. I missed those pieces of debris. One as a solder blob hiding behind one of the IC legs and the other is what I think is a small metal strand.
Or more likely a metal filing from me working on some other project totally unrelated to this memory cartridge project.
Luckily they didn't get a chance to short anything out . Here is some shots of them.

IMG_20210907_205040.jpg
IMG_20210907_205040.jpg (28.04 KiB) Viewed 590 times
IMG_20210907_204953.jpg


Actually, I think I learned some things by not having some of the circuits work. I focused on the importance of continuity checking. As I was doing this I noticed that all the memory ic chips pins are tied to each other barring 2 legs on each of the memory IC's. These pins are independently tied to different points of one of the 74138 logic chips.

I am going to have a look at what I could do better on the 3 PCB's that didn't work. Initially I did have myself grounded while soldering the memory IC's. However the memory IC's didn't seem to work. They showed up bad in the Neoram test program.
I will try a different strategy of using the kitchen sink as a ground on which to solder new memory IC's. While I am personally again grounded. Maybe this will help narrow down the margin of human error.
I'm not too concerned losing a few more memory IC's were cheap and it will help reduce the counterfeit chips from circulating in the market.
I would like to see if it's something that I could be doing better in my construction methods.
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by Zippy Zapp »

Nice job and great resources here. I will post pictures of the one I did a while ago. I don't recall if I tested fully the RAM. I know it works but I have to check to make sure it shows up as the full 2MB.

I will check out the tools you used for testing and the globs one that @eslapion posted in the other thread.

Thanks All for the great information!
Commodore - Changing the world 8 bits at a time.
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by Zippy Zapp »

Ugh. I tested mine and it only sees 512k. I must have did a crappy job soldering the SMD chips. It was the first attempt at SMD so I will give myself a break. I looked at it through a loupe and found some legs that aren't even on the pads all the way. And doing a continuity test between the chips found some that don't connect. Oh man I suck at SMD apparently. :lol:
Commodore - Changing the world 8 bits at a time.
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by banman »

Hi Zippy Zapp,

Not at all! I think you've done an amazing job. Well done.

I am very interested to see your pictures, please.


I know on my 3 PCB's that didn't work out I had legs that hadn't been properly soldered to the board. I used a pin and physically tried to move the soldered pins to see if I had made a proper connection.

Can I ask Zippy Zapp, what brand of memory you used and where you bought them from?


My biggest worry in my build was static discharge to the CMOS ram chips while attaching them to the PCB. I think that was my biggest undoing. Not sure....
I am thinking there needs to be a way to safely mechanically press the chip on the PCB temporarily to achieve proper electrical contact. This would allow for temporary testing of ram chips before final installation.
Alternatively is there a socket for this type of SOIC 32 pin memory chip? Maybe these chips aren't meant for use by the likes of me!




If you can locate a program called Neotunes, this is a good test for the battery backup part of the cartridge. I think this link is still valid....

https://csdb.dk/release/?id=98315

You can run the program again and again from a cold booted C64 by typing in the SYSXXX command that was in the original Neotunes program.



On a completely different topic has any one heard of the Sidekick64 cartridge? Looks interesting.
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