CPU swap if original is surface mounted

[bfollowell]

I haven't received my new 520STE yet. It's waiting to get through customs to become a U.S. citizen. Anyway, there's not a lot I can do besides speculate at this point. I'm hopeful that it will have a socketed CPU and other chips. It seems that the bigger percentage of STEs do, but there are some motherboard revisions where the CPU is surface mounted. Since Exxos has changing the CPU out to an HC type as a mandatory fix, what is the suggestion for this? Can you replace a surface mounted CPU with a socket? It seems like there would be no through-holes on the board if the CPU were surface mounted, but maybe I'm over thinking it. Anyway, on the off chance that mine comes in with a surface mounted CPU, how hard is it to replace the CPU?

If it's needed, would I replace the CPU with the PLCC68 Funky Socket Aadapter?
https://www.exxosforum.co.uk/atari/store2/#0113

Thanks!

[exxos]

You might be able to fit a SMT socket, but probably no point, just solder the CPU to the board instead. Though you need to be good at soldering to attempt it all though.

Ingo has the same issue here https://www.exxosforum.co.uk/forum/viewt ... ?f=24&t=68

And round up here https://www.exxosforum.co.uk/forum/viewt ... f=18&t=358

[derkom]

If you have a surface mount CPU in your STE, then you also have the "good" DMA chip, so the HC swap isn't necessarily indicated anyway.

[bfollowell]

Yes, but Exxos has debunked the whole "bad" DMA issue as a myth, which is why he pushes for CPU replacement.

Assuming I have a surface mounted CPU and a "good" DMA though, I guess I could leave it as is and check it out and see if it works with my Ultrasatan once I get it.

[exxos]

Yes, but Exxos has debunked the whole "bad" DMA issue as a myth, which is why he pushes for CPU replacement.

Assuming I have a surface mounted CPU and a "good" DMA though, I guess I could leave it as is and check it out and see if it works with my Ultrasatan once I get it.

If you have the 001A DMA then chances are you won't need to change the CPU. But there are machines which still malfunction with the 001A, so its not a guarantee the "good DMA" will solve the problems. The CPU change is a alternative (aka cheaper and easier) option instead of replacing the DMA chip (harder to obtain and more expensive) . Of course don't confuse "faulty DMA chips" with "DMA issues" as "DMA issues" are always there, but not down to a Faulty DMA chip.

What I was debunking was the -38 as being "faulty" on every STE. There has been no real evidence that any STE's had a faulty DMA chip. But DMA issues have always been there, even on STF machines, so I guess the -38 was faulty on them as well :)

[IngoQ]

IF you have to replace the CPU I'd recommend putting in a socket as I did in the thread that Exxos linked above.

You will need regular SMT PLCC sockets for this, where you can clip out the bottom. This way you can easily reach the solder pads which otherwise would be under the CPU respectively the socket. It's still not that easy, and I needed some practice runs on old board, but definitely doable.

[bfollowell]

I received my UK 520STE today. It has a GX-211 VO 2490 CA4003290 1989 motherboard with a socketed CPU and an integrated Blitter. I'm happy about the socketed CPU but it also has the supposedly "good" DMA that is marked C398739-001A (Atari-1990)-31, so I'm doubly pleased. It has UK TOS 1.06, which I'll be changing out soon, as part of the U.S. conversion process.

So, should I plan on replacing the CPU with an HC type, even with the supposed "good" DMA or try my luck with it as is? I was expecting to find two 256kb SIMMS but there are four, nine chips SIMMS installed, so this one may already be upgraded to either 1MB or 4MB. Or maybe they typically used 128kb SIMMs. Would that have been common then?

Anyway, now that I know what I have, I need to get a local order ready for all the fixes and an Exxos order in for a Dual TOS card and ROM. The only question I have is about the CPU.

Thanks guys.