130XE with 1MB RAM Needs Help.

[Stguild]

I have a 130 XE that has a 1MB upgrade in it. It works but it looks like a little kid installed it and its a mess. Is there anyone out there that could take it and reinstall it for me? You would need to clean up the wiring and resolder it all.

 

 

 

[+DrVenkman]

It would help if you indicated where in the world you're located and post a photo of the starting condition of said mess.

[Paul Westphal]

It might be the main system ram, especially if they are labeled “MT”

[Stguild]

I am in the US. Ohio. Her are a few pictures of the mess inside it. I also have no idea what the toggle switch does.

[TGB1718]

That looks terrible, not sure even a kid would make a mess like that ?

 

Whats under the black tape ? 

[MEtalGuy66]

That's not a 1meg XE.. 

That's a 320k..

 

How do I know? 

Only 2 additional PIA bits are used by that expansion (only 2 wires going to the PIA chip).

 

The 130xe used 2bits for extended ram in stock configuration..  Adding 2 more gives you 16 (2^4) banks of 16k.. 16 x 16 = 256...  So 64k base ram plus 256k extended.. Thats 320k..  Very popular upgrade..  

 

There's also the fact that there's only 1 bank of (256k)DRAM chips in the extended bank. They did make 1meg DRAMs but no one used them for homebrew atari 8 bit ram expansions because they require additional wiring to connect, and even more additional circuitry for refresh because ANTIC will not refresh that many address bits of DRAM by itself..

 

What's under the black tape, you ask? 

 

Probably a 74HC86..  You see the momentary push button on the back of the case? 

 

Hold that button and hit reset to cold-reset the machine without wiping out the contents of the extended ram..  You have to boot back up and use a special ramdisk handler to reconfigure the ramdisk without initializing it, but you can cold boot the machine and still have your data in ram.. 

 

Anywayze.. What you have there is a "Scott Petersen 320k upgrade", with a "Bob Wooley freezer switch" mod added.. 

 

It looks fine to me.. make sure there's no broken wires, and no exposed wires touching anything metal.. Put it back together and enjoy.. 

 

There are plenty of demos that use the extra ram, and you can use it as a 256k ramdisk in both SpartaDOS X, and disk based versions of SpartaDOS.. 

 

If I was you I'd either 

 

(a) leave it alone and enjoy your 320k XE... 

 

Or (b) Buy an "Ultimate 1 Meg" Expansion from Lotharek and find a competant hardware guy to put it in for you. 

 

Regards,

Ken Jones

Metalguy66

 

 

 

Edited December 14, 2019 by MEtalGuy66

[MEtalGuy66]

Wow. None of the old schoolers care to chime in here?

 

Anywayze, I have a few things further to add. 

 

I noticed that StGuild said in an earlier post:

22 hours ago, Stguild said:

I also have no idea what the toggle switch does.

Is it a Toggle-switch?  I assumed it was a momentary push-button. 

 

If it is in fact a toggle switch, then it has something to do with the way the PIA bits are used to address the expansion.

One popular "switch" of this sort that would be connected in such an upgrade was to change between "compyshop and rambo XL" similar banking schemes. 

Another was a "switch" to give back 1 bit of PIA control, reducing extended ram to 192k, but allowing separate ANTIC and CPU access to the currently selected extended bank. This is sometimes called "100% 130xe compatability mode".

 

At any rate, what you should do is download SatanTronic's XRAM prorgam and see which banks show up with various switch positions. 

 

This Demo, known as VBLITZ or VIDEO BLITZ used to be the definitive test of 130XE ANTIC Extended Video Mode.  (You have to unarc it first)

 

 

Lastly, here's a picture of a REAL 1meg upgrade, like we used to do back in the 80s.. Looks like it might have been done by the same guy who did your 320k. 

Notice he has not only replaced the extended bank with 256k DRAMs, but he's piggybacked an additional 3 banks of chips and hand-wired the address lines as necessary. 

 

I have forgotten what the various switches do, but you can bet they have to do with banking, compatability, etc.  

To get enough PIA bits for 1meg, you have to give up Internal BASIC, SELF TEST, Extended video, etc.

 

Scott Petersen was a hardware guy back in the 80s who came up with these upgrades and published them in step-by-step articles which would be distributed as text files on BBS systems. Most Atari user groups had a "hardware guy" that could install these types of mods for people.  

 

Petersen did the original 320k article, followed by a 576k, and finally a 1088k... 

Somewhere, I have all of the original text files, but I'm sure they are available in many places on the web. 

 

Oh well. Just thought I'd reminisce a bit, about the way we USED to do things, since STGuild brought it up. 

 

 

 

[cwc]

Petersen 130XE 320k Memory Expansion instructions:

 

https://www.exxoshost.co.uk/forum/viewtopic.php?f=44&t=732

 

https://www.atarimax.com/freenet/freenet_material/12.AtariLibrary/2.MiscellaneousTextFiles/showarticle.php?100