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4264 DRAM compatible with 4164?

tezza

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Hi Guys,

I'm repairing is old Atari 800XL board which gives a RAM error. It has MT4264 ICs soldered in. I've done some web browsing and it seems to me that NEC 4164 ICs are compatible with these.

I've got some spare 4164s so I got brave and tried the piggybacking technique to see if I could identify the offending chip. Sure enough, when the 4164 is piggybacked over one of the 4264's the machine passes it's memory tests and boots. In fact, it seems ok?

Before I go and socket/solder this in though, I just want to check with knowledgable people that these are indeed 100% compatible.

Does anyone know if they are not?

Tez
 

dave_m

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Tez,
I never heard of the 4264, but some searching showed that it is backward compatible with the 4164 but the 4164 is not upward compatible. This means if the Atari uses Page Mode in its design to speed up read/writes, the 4164 may not work. But who may know if they used 'Page Mode' addressing??

Here is a link to the Micron Technology 4264 part. http://generalthomas.com/Old_Test_Equipment/Micron4264.pdf
 

tezza

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Thanks guys.

It's a MT4264-15. Anyway, I cut out the old RAM IC and soldered in a socket. I've plugged the NEC D4164C in there, and I've had the ATARI ticking over in BASIC fairly successfully running a few loops and functions etc. Of course that's not to say it won't crash when it's doing something else.

I'm not sure if the Atari has a "page mode". I suspect it might as the two Atari 800XLs I know of both use the 4264 IC. I might have to track down some more documentation.

I'm investigating this as received a query on my own New Zealand Vintage computer forums from a guy with an Atari RAM problem. See
http://www.classic-computers.org.nz/forums/viewtopic.php?f=4&t=112

Anyway, by chance, I ALSO have a Atari 800XL board which has faulty RAM. It's one I've kept for spare parts. I wondered about the 4164 being a possible fix for this problem (they seem easier to obtain) so before I got back to the guy in the NZ forum I thought I'd try it out myself.

The jury is still out I think.

Tez
 

dave_m

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I've plugged the NEC D4164C in there, and I've had the ATARI ticking over in BASIC fairly successfully running a few loops and functions etc. Of course that's not to say it won't crash when it's doing something else.

Tez,
You would be better off running a good memory test with walking one patterns, etc, but it seems the 4164 will be OK.
-Dave
 

tezza

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Tez,
You would be better off running a good memory test with walking one patterns, etc, but it seems the 4164 will be OK.
-Dave

Yes, I might look for such a test over the next few days.

The Atari 800XL does a memory check when it first boots. That's why these problems are easy to diagnose. If the RAM wasn't compatible you would think that memory test would pick that up. But then again...it may not be a very sophisticated test. :)

Tez
 

Raven

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I have an Atari 800XL that I don't know anything about and have no cables for... I don't know how much it costs to ship back and forth from NZ<->USA but perhaps you have some spare peripherals, power adapter, etc...?
 

tezza

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Thanks for the offer Raven but we do get Atari 800XLs appearing here from time to time. Some of the scruffier ones just go for a few dollars.

As the one I've just worked on is a junk machine for spare parts I'm not going to worry about fixing it too much. But for Nathan though (the guy who posted in the NZ forums) his best option might be to look for a scruffy but working ATARI on our TRADE ME site and swap the boards, or get hold of a broken one (even cheaper) and solder out a RAM chip if he has the skills.

Alternatively he could look for 4264 ICs out here in the wild here in NZ somewhere. I don't fancy his chances with this option.

For myself I'm now curious as to whether or not the Atari 800XL does indeed NEED the MT8264 ICs that seem to be soldered in there, and whether an 4164 is an acceptable substitute.

Some research is in order I think. I need to find out if "Page Mode" addressing is used by the Atari 800XL at all. From what Dave_m said, this seems to be the main difference between the two.

Tez
 

Chuck(G)

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Next time, you need to specify the prefix to the part number. The Matsushita MN4264 is not the same as the Micron MT4264. Confusing, huh?

You're probably all right with a 4164, depending on its date and manufacture. For example, the KM4164B from Samsung also has Page mode, as does the TI TMS4164.
 

tezza

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Very Confusing.

But with respect Chuck, I did say MT4264 in my very first post so the prefix was there :)

What is needed on the web is some kind of "at a glance" site, which has a large table of RAM ICs, showing equivalents from the many different manufacturers. Perhaps such a thing would be just too large, but there certainly is a confusing morass of names and numbers out there.

Tez
 

MikeS

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Very Confusing.

But with respect Chuck, I did say MT4264 in my very first post so the prefix was there :)

What is needed on the web is some kind of "at a glance" site, which has a large table of RAM ICs, showing equivalents from the many different manufacturers. Perhaps such a thing would be just too large, but there certainly is a confusing morass of names and numbers out there.

Tez
You've got him there, Tez ;-)
Besides, 4bit DRAMs usually have 18 pins so you wouldn't be able to piggyback a 16 pin chip...

But you're right; the numbers are indeed confusing in many cases, especially RAM chips; most of the time you can ignore the manufacturer's prefix, but once in a while the same number does refer to two different types.

As it happens I'm just cataloging and inventorying some RAM and EPROM chips; lots of fun...

Here are a couple of somewhat incomplete lists; no small DRAMs, but better than nothing...:

http://www.serve.com/macsite/ChipMerRamGuide.html
http://www.infinityelectronics.com/crossref.htm
 
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tezza

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As it happens I'm just cataloging and inventorying some RAM and EPROM chips; lots of fun...

I'll bet (-NOT!) :) . Are you going to publish it somewhere when done Mike?

Incidently, I managed to obtain a copy of SAMS Computerfacts for the Atari 800XL. They specifiy the RAM type as HM4864P-2 (??). Replacement types are listed as General Electrinc 4164-15, NTE4164 and ECG2164(!!). Not a sign of a MT4264-15, which were the ICs actually in the thing.

No mention of the NEC 4164C-15 I used as a replacement either but based on the other compatible ICs I think it will certainly be ok.

Obviously there was some but not a lot of standardisation of nomeclature regarding RAM ICs back in those days. Is it because there was no overall international body setting naming conventions? Many manufacturers just thought of a number for their ICs and called them that?

Tez
 

Raven

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Thanks for the offer Raven but we do get Atari 800XLs appearing here from time to time. Some of the scruffier ones just go for a few dollars.

As the one I've just worked on is a junk machine for spare parts I'm not going to worry about fixing it too much. But for Nathan though (the guy who posted in the NZ forums) his best option might be to look for a scruffy but working ATARI on our TRADE ME site and swap the boards, or get hold of a broken one (even cheaper) and solder out a RAM chip if he has the skills.

Alternatively he could look for 4264 ICs out here in the wild here in NZ somewhere. I don't fancy his chances with this option.

For myself I'm now curious as to whether or not the Atari 800XL does indeed NEED the MT8264 ICs that seem to be soldered in there, and whether an 4164 is an acceptable substitute.

Some research is in order I think. I need to find out if "Page Mode" addressing is used by the Atari 800XL at all. From what Dave_m said, this seems to be the main difference between the two.

Tez

I think you misunderstood - I was asking if you had spare peripherals you could sell/ship to me - I actually had considered selling it to you first, but I promised someone who gave it to me that I'd hold onto it and not sell it.
 

Chuck(G)

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Incidently, I managed to obtain a copy of SAMS Computerfacts for the Atari 800XL. They specifiy the RAM type as HM4864P-2 (??). Replacement types are listed as General Electrinc 4164-15, NTE4164 and ECG2164(!!). Not a sign of a MT4264-15, which were the ICs actually in the thing.

That doesn't surprise me. Micron was fairly late in the DRAM game and didn't really ramp up production until the DRAM shortage of the 80's. Back when 16K DRAMs were all the rage, I remember that we compared a number of vendors (Intel, Motorola, NEC, etc.) and found wide variations in electrical characteristics. One thing I recall was that an Intel 2117 would last a few milliseconds without refresh before it started to drop bits, while a NEC uPD416 DRAM could last for several seconds.

When you're dealing with parts of that era, you have to be somewhat careful. For example, most 2716 EPROMs are single-supply, but the TI TMS2716 is 3-supply. And many EPROMs wti the same number had wildly different programming algorithms.
 

tezza

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I think you misunderstood - I was asking if you had spare peripherals you could sell/ship to me - I actually had considered selling it to you first, but I promised someone who gave it to me that I'd hold onto it and not sell it.

Ah. No, I don't have any spares, sorry.

Tez
 
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