A little bit of 8 Bit: 65XE upgrade to 128k RAM

[ChaoticBiker]

Thank you all for responding to this.
As another update - well it wasn't the +5v that was causing the problem.
It was the Mitsumi 56-3217 keyboard mylar that apparently decided it had enough of being pulled in and out of the slot.
The joys of working with >30 year old electornics
Also this is now the 3rd Atari of mine where the power led stopeed working (suspected for same reason - worn/cracked mylar)

[rubber_jonnie]

Another fault diagnosed

[JGroth]

Code: Select all

CHIP    XE_320k    GAL16V8    SIMPLE_MODE

A14    A15   pb2   pb3      pb4      cas     pb6    pb7  mode  GND
mhalt  ra8   map   casbank  casmain  fa_14   fa_15  pb5  phi2  VCC

 fa_15        = A15
              + A14 & pb3 & /pb4 & mode & mhalt
              + A14 & pb3 & /pb5 & mode & /mhalt;

 /fa_14       = /A14
              + /A15 & /pb2 & /pb4 & mode & mhalt
              + /A15 & /pb2 & /pb5 & mode & /mhalt;

 casmain      = /phi2
              + cas
              + /A15 & A14 & /pb4 & mode & mhalt
              + /A15 & A14 & /pb5 & mode & /mhalt;

 /casbank     = /A15 & A14 & phi2 & /pb4 & /cas & mode & mhalt
              + /A15 & A14 & phi2 & /pb5 & /cas & mode & /mhalt;

 /map         = pb4 & pb5 & /pb7;

 ra8          = /phi2 & pb6 & mode
              + phi2 & pb7 & mode;

The LS7495 must be placed at the positon of U35. The GAL - bent pin 7, 8, 9,12 and 13 up - will be placed in U34. Connect pin 7 of the GAL to pin 16 of PIA and pin 8 of the GAL to pin 17 of PIA. Pin 9 can be left open (expansion enabled) or closed by switch to ground to disabled the expansion. Pin 12 via 33 Ohm resistor to the pin 1´s of the 8 DRAMs (memory addressline A8) and pin 13 to the pin 6 of MMU. This pin must be also bended, so better is to desolder the MMU, fit it into a socket and replace it with pin 6 bend up.

I make several years ago an article for the ABBUC magazine no. 95. You can download it here, but the text is only in german - sorry.

Jurgen

Sorry to resurrect an old post but I'm curious on which 65XE motherboard this expansion works? I'm particularly puzzled by the connection between GAL pin 7 (PB6) and PIA pin 16 (PB6) as on my mother board that PIA pin isn't connected to anything. So what is that connection supposed to do?
I just wonder because I'm considering upgrading my 65XE using this. The motherboard I've got is a CO70067, exactly the same mother board used in a 130XE with 128k of memory.

Regards,
JGroth

[tfhh]

Hi,

sorry beeing late to the party. I read you already fixed the problem

As another update - well it wasn't the +5v that was causing the problem.
It was the Mitsumi 56-3217 keyboard mylar that apparently decided it had enough of being pulled in and out of the slot.
The joys of working with >30 year old electornics
Also this is now the 3rd Atari of mine where the power led stopeed working (suspected for same reason - worn/cracked mylar)

Yes, these is "usual" with the XE keyboards. Don´t know if somebody point it out, but new (really new - not "NOS") mylars are availible from Retronics and some other sellers, just search at eBay for "atari membrane" and you should get it.

[tfhh]

Hi,

Sorry to resurrect an old post but I'm curious on which 65XE motherboard this expansion works? I'm particularly puzzled by the connection between GAL pin 7 (PB6) and PIA pin 16 (PB6) as on my mother board that PIA pin isn't connected to anything. So what is that connection supposed to do?
I just wonder because I'm considering upgrading my 65XE using this. The motherboard I've got is a CO70067, exactly the same mother board used in a 130XE with 128k of memory.

This expansion worked that way in all XE versions where an unpopulated U35 is found. By default all XE models are possible, which have the places for 16 pieces of DRAM. Some rare XE mainboards have only one column with 8 DRAMs, these are models where "900XLF" is found on the solder side of the PCB and they have no ECI - only a cartridgeport.

Some XE mainboards have only 4 resp. 2 DRAMs in place, these are 4-Bit DRAMs. My solution would work here, too - but Atari didn´t include the location U35 on these mainboards. If you have such model, I can modify the GAL code, but you need then a 22V10 instead of a 16V8 and two more wires.

But, just to have say it, there are much easier ways to get 512 KB expansion memory based on SRAM instead of the DRAM expansions. Removal of the eight 4164 DRAMs at the 2nd bank, de-soldering/empy the holes, install new sockets, the 41256 DRAMs, a GAL... it´s a nice way to tinker around, sure, but more effective are SRAM based expansions today.

[aotta]

Hello everybody! i found this great thread about 65XE ram upgrade, but just discovered mine has a 130XE(64x4) motherboard with unpopulated U11, U12 and U35: since aren't more available on ebay the C25953, is there a way to program a GAL for replacing it?

[rubber_jonnie]

Hello everybody! i found this great thread about 65XE ram upgrade, but just discovered mine has a 130XE(64x4) motherboard with unpopulated U11, U12 and U35: since aren't more available on ebay the C25953, is there a way to program a GAL for replacing it?

If you look earlier in the post, somebody has used a GAL to do a 320KB upgrade. Personally I have upgraded to Ultimate 1MB since I made this post, so haven't followed up any further along those lines.

[aotta]

If you look earlier in the post, somebody has used a GAL to do a 320KB upgrade. Personally I have upgraded to Ultimate 1MB since I made this post, so haven't followed up any further along those lines.

I red about 320k upgrade, but I think a different gal (22v10) and a new jed files it's needed for mb without c34 like mine.
Anyway, I followed your suggestion, and just ordered an ultimate 1mb! Thank you!

[rubber_jonnie]

If you look earlier in the post, somebody has used a GAL to do a 320KB upgrade. Personally I have upgraded to Ultimate 1MB since I made this post, so haven't followed up any further along those lines.

I red about 320k upgrade, but I think a different gal (22v10) and a new jed files it's needed for mb without c34 like mine.
Anyway, I followed your suggestion, and just ordered an ultimate 1mb! Thank you!

I have an 800XL and a 65XE, both with Ultimate 1MB, I am very pleased with them. Also recently upgraded to VBXL/XE for super clear video out on both too. I also got a Side3 cart and whilst it has some minor issues that FJC is working on, it really is great.

I can also recommend an SDRIVE-MAX too.

[aotta]

I have the sdrive max, that I use with 65xe and with my 800xl, but I think I'll upgrade only the 65, because the 800 is boxed and I take it out from its polys rarely, to preserve them!
I'm very interested in VB/XE too, I use RGBtoHDMI for most of my retrocomputer, and I am waiting for the OSSC+koryuu i bought some days ago for digitalizing the composite output of the Atari's ones, but if it won't work as expected, I'll go for the VB/XE solution too!