Question - MT Ram

[deffroe]

Hi all,

Is all MT4264 ram bad/to be avoided?  I've seen on here where first question asked about a faulty machine is Does it have MT.  In the early days of covid, before the first lock down I picked up 3 dirt cheap C64 breadbins(hooock puhh🤢) and it was pretty similar on their forums.

Was there a period where they are typically bad or are all MT considered bad?

Reason for asking is, in case of the C64's that had MT ram was from '83/'84 did have issues and needed changing. My two 800XL's both have MT from '83/'84 and so far, touching lots of wood, are running fine.

The 65XE non-ECI has MT ram from '87, well 7 chips are the other is a mitsubishi M5K4164.

Is the reputatioin of MT ram from a bad batch or is it all bad?

 

Regards

 

Phil

[Beeblebrox]

not sure about batches but yes, generally avoid MT ram.  Notoriously unreliable, cheap and nasty.

 

here are alternatives:

 

Edited November 20, 2022 by Beeblebrox

[Mclaneinc]

The reputation of MT ram is so bad that pretty much every repair person on youtube etc, instantly say remove it all, it will go bad..

 

I think the C64 gets more of a bad rep because they were cheaply made in the first place and probably added to the strain on the notorious ram. While I can't vouch 100% about the ram as I don't have the sort of repair experience many people on here have got, I tend to trust the number of reports of it being awful and needing to be changed asap.

[deffroe]

2 minutes ago, Mclaneinc said:

The reputation of MT ram is so bad that pretty much every repair person on youtube etc, instantly say remove it all, it will go bad..

 

I think the C64 gets more of a bad rep because they were cheaply made in the first place and probably added to the strain on the notorious ram. While I can't vouch 100% about the ram as I don't have the sort of repair experience many people on here have got, I tend to trust the number of reports of it being awful and needing to be changed asap.

Yeah, I've pretty much followed the same advice, usually changing ram 'just in case'.  Just got me thinking seeing ram from a much later date if it was still just as bad.

I'll be ordering some more chips in to be on the safe side.

 

Phil

[Beeblebrox]

It's a no brainer to swap out MT ram chips if they al ram are already socketed. However if not socketed obviously you run the risk of damaging the PCB and vias, tracks lifting etc whilt socketing.

 

Ram chips are relatively cheap so if already socketed go for it. If not it may just be a case of running with the MT ram if they are ok at present.

[deffroe]

21 minutes ago, Beeblebrox said:

It's a no brainer to swap out MT ram chips if they al ram are already socketed. However if not socketed obviously you run the risk of damaging the PCB and vias, tracks lifting etc whilt socketing.

 

Ram chips are relatively cheap so if already socketed go for it. If not it may just be a case of running with the MT ram if they are ok at present.

Cheers bud!

As you'd expect, XL's are socketed and the XE isn't.  I'll get some ordered in ready for the failures

 

Phil

Edited November 20, 2022 by deffroe

[erichenneke]

I have definitely root-caused memory issues back to specific chips that were MT ram far more often than other brands.  But if they are soldered down and doing fine i'd leave it alone. 

 

I always chunk the bad MT chips in the garbage when I root-cause them as actually being bad of course, but otherwise I keep them around and use them(in sockets) and have a bunch of them that have been in use for many many years without problems.  So I don't think it should be quite so black and white, especially if they are soldered in.   

 

But for sure, if you have a machine that uses any MT and the system starts doing anything goofy... that's the FIRST THING to check are those MT ram chips!   Oh, and for God's sake, don't solder any MT ram into new places they aren't already soldered into for any reason! 

 

Eric

[+bf2k+]

I had two 130XEs go bad in November 2021 within 1 week of each other.. both with mtram in them...

[TGB1718]

6 hours ago, bf2k+ said:

I had two 130XEs go bad in November 2021 within 1 week of each other.. both with mtram in them...

I know one of my 130XE's has them "living on a knife edge"  

Not checked the other one as it's a "stock" machine and only ever opened to fix a keyboard matrix

[TZJB]

17 hours ago, deffroe said:

Cheers bud!

As you'd expect, XL's are socketed and the XE isn't.  I'll get some ordered in ready for the failures

 

Phil

Any DRAM can fail. As well as MT I have had Samsung DRAM go bad with 6 out of 8 chips in a 800XLF. I was a bit flabergasted for that many to have bit rot. Generally speaking if one MT DRAM chip goes bad then I change them all, but if they are still working now they are probably good ones. I also upgrade them for 41256 chips as I have run out of 4164 chips and have loads of 256K. They work fine at 64K and obviously can be used later for memory expansion.

[Mclaneinc]

Yeah any DRAM can indeed fail but MT is just the joke ram chip of the bunch, while ram can fail, MT will fail.. Really annoying as the Atari range seemed to use quality components unlike the C64.

[deffroe]

5 hours ago, TZJB said:

Any DRAM can fail. As well as MT I have had Samsung DRAM go bad with 6 out of 8 chips in a 800XLF. I was a bit flabergasted for that many to have bit rot. Generally speaking if one MT DRAM chip goes bad then I change them all, but if they are still working now they are probably good ones. I also upgrade them for 41256 chips as I have run out of 4164 chips and have loads of 256K. They work fine at 64K and obviously can be used later for memory expansion.

That's interesting, there's a post I've read somewhere where Samsung was recommended and I've used as replacements on one of my C64's(hock pugghh).

Also, the 41256's are drop in replacements? This will open up the scope when sourcing chips.

[mimo]

I've just fixed a friends 800XL. Nothing socketed so replaced the RAM first as it was MT, that didn't fix the fault. Next on the hit list was the CPU. Bingo! ANOTHER mexican CPU dead. I've had three so far this year, two in XEGS machines and one in this XL.

Put the MT ram back in and it works fine, but my friend decided to fit new RAM anyway.
The XL has Basic rev C installed from factory, which was a surprise as I've never seen an XL with that rev fitted 

[mimo]

14 hours ago, deffroe said:

Also, the 41256's are drop in replacements?

Yes, but I found it harder to find those last week than the standard ones 

[xrbrevin]

On 11/20/2022 at 7:09 PM, deffroe said:

The 65XE non-ECI has MT ram from '87, well 7 chips are the other is a mitsubishi M5K4164.

 

ive seen this before. DRAM #1 has more 'responsibility' in the circuit than the other 7x. I think its called a 'tag chip' but clearly the MT DRAMs can struggle so Atari fitted 1x decent DRAM and 7x cheap ones. Maybe someone more informed can elaborate?

 

15 hours ago, deffroe said:

Also, the 41256's are drop in replacements? This will open up the scope when sourcing chips.

yes they are pin-compatible and work as 4164s do. you can also use them in the 2nd bank of an XE as part of the 320XE mod.

 

[+x=usr(1536)]

2 hours ago, mimo said:

The XL has Basic rev C installed from factory, which was a surprise as I've never seen an XL with that rev fitted

A very small number of the late PAL 800XLs had it - we had a couple in our user group at the time.  Both machines had been bought new with it installed.

[woj]

I am probably an exception from the rule, but I got a "for parts" 800XL couple of months ago, it had MT RAM in it, sitting in the attic for who knows how long, and it was all good. The computer did have some stability issues with SIDE3, the RAM was replaced out of principle, along with a couple of other things (74LS08 in particular), and the computer seems now fine. All in all, I do not think this RAM was bad in any way...

[TZJB]

On 11/21/2022 at 8:07 PM, deffroe said:

That's interesting, there's a post I've read somewhere where Samsung was recommended and I've used as replacements on one of my C64's(hock pugghh).

Also, the 41256's are drop in replacements? This will open up the scope when sourcing chips.

I agree that normally I would recommend Samsung DRAM too, it must have been a bad batch, you just never know. The same 800XLF also had a faulty CPU so I had a double whammy. 41256 chips only have an extra adress pin compared to a 4164. Pin 1 A8 are clamped high in an 800XL so a 41256 is technically a drop in replacement. Pin 1 is left floating in a 130XE to save money, but nevertheless seems to work just fine with the 41256 in either of the two 64K banks, but restricted to 64K in each of the banks without extra wiring and components in the second bank (unless anyone knows how to enable 256K in both banks)?