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

[pancio]

Hi,

A few years ago I designed PCB for Atari 65/130XE based on HIAS 512KB SRAM project. Some colleagues asked me about version for Atari 800XL with FREDDIE. Today I added data regarding A800XLF version to article:

https://systemembedded.eu/viewtopic.php ... 0&p=49#p49

It's very easy to assembly and run. Personally I'm using this mod in my two 65XE without any issues. This is not tested yet because I'm waiting for first part of PCB. Of course anyone might collaborate - I'm open for any suggestion for changes

Have fun!

[Mathy]

Hello pancio

Does it use $D301? Which pins? Internal or external?

Sincerely

Mathy

Edit: Seems to be internal.

[pancio]

All required pins from PIA are connected internally on board using "piggy" method (PIA must be de soldered and inserted to the memory board). Yes, it use PIA port B and it's Rambo/CompyShop compatible. You need to connect only 3 additional signals: CASINH_IN, CASINH_OUT and MAP_OUT directly from MMU chip.

Some users which using PokeyMAX or Dual Pokey Mod, might have an issue to place SRAM module because of PCB dimensions. Yesterday, together with SuN we're rebuilder PCB design to avoid this inconvenience...

A800XL PCB layout v.1.1

now we have much more space under PIA chip and other mod might me installed without any issue.

SRAM module + Stereo MOD

[Mathy]

Hello pancio

So you can have 512kB of extended memory in both RAMBO and Compyshop mode? I especially like Compyshop mode because it has separate ANTIC and CPU access. How hard would it be to expand this to 1MB and make this work like my 1MB upgrade? In my upgrade, I freeze the BASIC, OS ROM/RAM, selftest and in the XEGS even Missile Command when either PB4 or PB5 or both go low.

Sincerely

Mathy

[pancio]

I'm not sure... how to upgrade mod to 1MB. As I remember I asked Hias on AtariAge about this but probably GAL22V10 is not capable to have program to handle so big memory. Probably we should change GAL to some small XILINX. I don't know that I can do it. Second reason, this mod everyone which have little experience with iron can do this mod himself . But we will see

Hias provide two jumpers for memory configuration:

The extension can be configured to 4 modes (using 2 switches or jumpers):

0k / off
256k - using PortB bits 2, 3, 5, 6 (compatible with the "Atari Magazin" ramdisk)
256k with separate Antic access - using PortB bits 2, 3, 6, 7 (Rambo/CompyShop compatible)
512k - using PortB bits 2, 3, 5, 6, 7

[Mathy]

Hello pancio

My upgrade uses port B bits 0, 1, 2, 3, 6 and 7.
If port B pins 4 and 5 are high, bits 0, 1, 6 and 7 work as usual.
If either bit 4 or bit 5 or both go(es) low, the status of BASIC, OS ROM/RAM, Selftest and Missile Command (XEGS only) is frozen and bits 0, 1, 6 and 7 only control expanded RAM (as do bits 2 and 3).

Sincerely

Mathy

[pancio]

SRAM 512K with battery backup for Atari 800 XLF is pretty ready to use... now I'm looking for candidate for upgrade

SRAM 512K for A800XLF

[Olix]

I have an Original 800 XL with Freddie (PAL) with No RAM Extension and would Like to Test the board. Ist ist possible to geht one? It could be a naked one without parts. I have the parts and skills to solder.

[pancio]

Hello Olix,

Sure, it's possible. I've a few PCBs which I may sell. Today I run one module with 800XL without Freddie (yes, it's possible too - I didn't realize about it) I may summary with a few sentence:
- only 320KB is visible at this moment. I checked banks using MEMTEST v1.0. Seems like no 7bit is using. It will be investigated.
- there is no possible to close top case if you are using sockets under main chips (CPU, PIA and GAL).
- SELFTEST can check only 24KB and starting again

So at this moment it's not ready for use at all or my stock Atari 800 XL is broken (e.g. PIA or stock RAM).