RAM 512KSRAM extension module for Atari 65/130XE and 800XLF

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pancio
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RAM 512KSRAM extension module for Atari 65/130XE and 800XLF

Post by pancio »

This article will show how to build, assembly and use the SRAM 512KB memory extension, This is my own modification based on Matthias Reichl aka Hias SRAM v1.3 from https://www.horus.com/~hias/atari/#sram512k page. It's my adaptation and it's prepared for some 65XE and 130Xe Atari computers. You may follow the discussion with topic (Polish) on http://www.atari.org.pl/forum/viewtopic.php?id=15938 regarding any doubt, issues and solutions.

Project was made as Free Hardware under Creative Commons BY-NC-SA 4.0.This means - you can do it yourself, for private use. Commercial use is possible after obtaining the authors' consent.

Change log

Code: Select all

2019-05-11: Initial version for Atari 65XE/130XE with ECI.
2021-09-16: Version 1.0 for Atari 800XLF designed. The same hardware mod for Atari 800 XL with FREDDIE chip. Please find attached zip file with gerbers on the bottom of article.
2021-09-18: Version 1.1 for Atari 800XLF designed. To avoid conflict with Simple Stereo MOD or PokeyMAX.

Why?
Well, on the market you may find so many Ram extension for your Atari but...
- this one is Static RAM (less power consumption)
- only 3 wires are necessary (if you have socketed CPU, PIA and MMU)
- RAMDISK feature after power off the Atari.
- very cheap RAM


Let's start.
Matthias doesn't publish any PCB so I had little much work to do. At first I rearranged schematic in order to use piggy style assembly - I decided to use CPU as a base with full data and addresses buses. Additional I decided to place CPU and PIA on the same PCB as piggy. It's possible that in 65XEN both ICs are closer together. So, the schematic contains two piggys:
SRAM 512k schematic
SRAM 512k schematic
sram13v5.png (47.63 KiB) Viewed 62738 times
Prototyping and Manufacturing
This mod is my first which I made with KiCAD. I can't work anymore with Autodesk Eagle because of it's limitations (PCB size, price). The KiCAD is so powerful as well. Matthias provided his project with Eagle format but KiCAD has very good import tool. Of course some corrections were necessary with used part on schematic. When I rearranged all wires I made a few prototypes on paper in order to match to Atari's motherboard.
SRAM 512k paper prototype
SRAM 512k paper prototype
After a few trials the PCB was done:
SRAM 512k PCB KiCAD
SRAM 512k PCB KiCAD
SRAM 512k PCB KiCAD 3D
SRAM 512k PCB KiCAD 3D
Well, regarding PCB manufacturing I may say only: never expect so much. On Polish market we have many PCB supplier but the price is rather terrible. I tried many China market company with rather good result for best price. This time I chosen JLCPCB because they have very good price with so short delivery time! (4 days! for production and delivery).

That's result:
SRAM 512k PCB RED
SRAM 512k PCB RED
The quality is very good so I will recommend this company for prototyping process

Assembling

At first I burned GAL chip with new logical matrix from JEDEC file from Matthias's page:
XGPRO GAL22V10 programming
XGPRO GAL22V10 programming
Next step is necessary if you have not socket ICs. In my case I desoldered CPU, PIA and small MMU and socketed. Pin 6 and 16 of MMU should be cambered to up and soldered to wired on memory board. The same with 16 pad of MMU socket (see schematic):
Atari 65/130XE socketed and prepared for extension
Atari 65/130XE socketed and prepared for extension

then assembly all on extension board:
SRAM 512k PCB assembled
SRAM 512k PCB assembled
and finally result:
,
SRAM 512k on motherboard. Final result
SRAM 512k on motherboard. Final result
Test
It was terrible... you may find some details on http://www.atari.org.pl/forum/viewtopic.php?id=15938
I thought that something is wrong with extension because demo Videoblitz doesn't work properly...

Well, many hours testing, colleagues suggestions from http://www.atari.org.pl/forum ... and the final result was found...

Version for Atari 800XL (with FREDDIE)
Important notice:
There is an issue with using GAL 150 ns access. Please use slower GAL! (e.g. 250ns)

PCB view
PCB view
sram512_800XLF-01.png (157.71 KiB) Viewed 53137 times
PCB 3D view
PCB 3D view
sram512_800XLF-02.png (637.64 KiB) Viewed 53137 times
Version for Atari 800XLF (with FREDDIE) and additional Simple Stereo or PokeyMAX mod
PCB design v1.1
PCB design v1.1
sram800xl-v1.1.png (136.35 KiB) Viewed 53129 times
v1.1 first check
v1.1 first check
SRAMplusSTEREO.jpg (131.09 KiB) Viewed 53129 times
1024KB version
Based on Hias's 1024KB extension
Based on Hias's 1024KB extension
1024KB-SRAM_based_on_HIAS_512KB_ext.png (223.27 KiB) Viewed 23841 times
Attachments
sram13v5.zip
KiCAD project (XE version)
(67.33 KiB) Downloaded 1826 times
sram13_gerber.zip
Gerber files for 65XE RAM EXT
(175.53 KiB) Downloaded 1783 times
SRAM512KB_MOD_ATARI800XLF_V1.1_gerbers.zip
(69.91 KiB) Downloaded 1802 times
sram512_A800XLF_gerber.zip
(94.81 KiB) Downloaded 1846 times

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