Replacing an MMU (344-0010-B)

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Replacing an MMU (344-0010-B)

I need to replace the MMU (part number 344-0010-B) on an Apple ][e.  Does anyone know of anywhere I can buy one?  Alternatively, does anyone know if it is possible to burn some kind of blank logic IC in order to reproduce an MMU?

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Is this the same part that

Is this the same part that gets replaced in a PAL IIe to change display line count and produce 50 Hz update? If so then it is a ROM and could in theory be replaced if you can read out the contents from a similar one. I guess the pinout might not be standard though. There is definitely info around about how it works and what each line does. I don't have it handy now but could search for it.

cheers, Nick

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344-0010-B

I found this site on the web: https://www.4starelectronics.com/part_detail/3440010B.html

 

I found others sites as well, but they all link back to the same company. To me, that technique is related to scams.

 

For some reason, every site was you to request a quote.

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This schematic shows how the

This schematic shows how the MMU is connected:

https://downloads.reactivemicro.com/Apple%20II%20Items/Hardware/IIe/Schematic/Apple%20IIe%20Schematic%20-%201.jpg

It seems to be acting as a DRAM controller, it basically buffers the address bus from the 6502 onto the DRAMs and performs some decoding logic. Unfortunately the decoding is pretty complicated because of the different modes and so on that the machine can be in. There are some other schematics in the same directory which seem to show the internal logic (I think may be leaked schematic of Apple IIe prototype hardware). So it's not easy to make one's own -- probably possible using a CPLD, but would be a months long project so not something I would tackle, and also the result would be a bit ungainly since it would sit above the PCB in an adapter PCB to get it into the 40 pin pinout.

The best option is to buy one. Surely it must be possible to buy an Apple IIe motherboard from a failed machine to use for parts?

cheers, Nick

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MMU stands for Memory

MMU stands for Memory Management Unit.

It actually combines and replaces a bunch of TTL logic chips. The MMU internals are covered into the Understanding the Apple IIe book by Jim Sather (see chapter 5).

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I have one spare from a parts

I have one spare from a parts mainboard. 

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Thanks Timelord, I've sent

Thanks Timelord, I've sent you a DM

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Thanks amauget, I didn't know

Thanks amauget, I didn't know the MMU was covered in that book.  As apple basically introduced the MMU as a way of stopping other companies cloning their hardware, I guessed that finding any documentation on it was probably unlikely.  I'd considered trying to work out what might be in the MMU by comparing a IIe schematic and a II or II+ schematic, but that is a last resort.  I may look at recreating the MMU using the information in Understanding the Apple IIe though.  For now I'm hoping I can get an original IC, but I will probably still try and come up with an alternative as they are only going to become rarer and it would hopefully be useful for others.

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MMU and IOU analogues

I came across 2 sets of analogues for the MMU and IOU in A2 clones:

N4006 and N4007

CM631 and CM632.

The latter pair is with the letters written in cyrillic alphabet as these were manufactured in Bulgaria back in the 1980's.

 

 

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The MMU and IOU chips on a /

The MMU and IOU chips on a //e are custom VLSI parts made for Apple, and haven't been made since they quit making the //e over 25 years ago.  Most of the NOS (New, Old Stock) parts have been used up over the years.  A few people may have one, but mostly the only way to find one these days is to scavenge it used off a motherboard from a machine that is being parted out.

 

It might be possible to make a replacement using a programmable chip like an FPGA mounted on a 40 pin DIP carrier, but as far as I know nobody has done that yet.  One of the issues these days is most of the FPGA chips out there are designed for lower power than the 5V used in a //e which means that all the signal levels would need to be converted and fitting all of that for as many signals as are handled by the FPU and MMU on a 40 pin DIP package would be a challenge.  It could be done, but there does not appear to be, at least not yet, sufficient demand to make it worth someone's time to do it.  There are probably enough donor machines to keep the prices down for a while given the number of millions of //e units Apple made back in the day.

 

 

 

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rpalaveev wrote:I came across
rpalaveev wrote:

I came across 2 sets of analogues for the MMU and IOU in A2 clones:

N4006 and N4007

CM631 and CM632.

The latter pair is with the letters written in cyrillic alphabet as these were manufactured in Bulgaria back in the 1980's.

 

Those were also custom ASICs and were probably only made for a few years, and in much smaller quantities than the Apple parts.  Clones of the //e were far less common than the ][+, not only because it was harder to copy due to the custom chips, but also because Apple aggressively tried to get the US Customs to shut down imports.  Clones of the //e mostly came from Tiawan or Hong Kong, but they were also made in several other countries including Brazil and a few eastern bloc countries like Bulgaria.  Some of these were direct copies and the MMU and IOU equivalentrs were actually possibly interchangeable (albeit I'd b e real careful with that) and in other cases they just developed their own compatible design.

 

The thing is that I'm sure it is even harder to find the chips you mention above than Apple pars, and the clone units they were made for are generally going to be worth far more than a //e is, due to being much, much, more rare.  Apple made several million //e systems over around a 10 year period.  Most of these clones were on the market only a couple years at most, and generally were not imported into the US in large quantities due to the aforementioned Customs issues.  So collectors will often pay a fair amount for them.

 

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One of the reasons why //e

One of the reasons why //e clones happened in some countries like Brazil is the protectionist trade laws there.  At least in those days, it was prohibited to sell foreign made computers in order to encourage the local industry.  Of course countries like Bulgaria were "behind the iron curtain" as they were controlled by puppet governments of the Soviet Union, and in general were not allowed to trade with the west much.  They had to develop their own systems because even if they were allowed to import from the west, they didn't really have hard currency that was exchangable.  Most of these countries never really tried to export outside of their regions.  Brazil mainly to other South American countries and Bulgaria in the other 2nd world countries of eastern europe.  India also had similar protectionist trade laws to Brazil, but I don't recally that I've ever seen an Indian made Apple II clone, although maybe there were, and they just weren't exported or something.  Hard to imagine a few collector examples wouldn't be over here though, like the Chinese CEC machines for example that were never intended to be exported, but you still see in the US occasionally.

 

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I tbeleive IIe clones were a

I tbeleive IIe clones were a lot more common in Canada. I think Apple wasn’t as able to stop them coming in here. The two I had were exact copies of the IIe, all the parts were interchangeable. I gave them and some II+ clones to an American collector about 15 years ago. I’m not a collector so I didn’t have much of an interest. Though collectorism has raised it’s head a couple of times.

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Wayne wrote:I tbeleive IIe
Wayne wrote:

I tbeleive IIe clones were a lot more common in Canada. I think Apple wasn’t as able to stop them coming in here. The two I had were exact copies of the IIe, all the parts were interchangeable. I gave them and some II+ clones to an American collector about 15 years ago. I’m not a collector so I didn’t have much of an i

You are probably correct about //e clones being more common in Canada.  Apple would not have had the same kind of influence over your Customs to keep them out.

 

 

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Wayne wrote:I tbeleive IIe
Wayne wrote:

I tbeleive IIe clones were a lot more common in Canada. I think Apple wasn’t as able to stop them coming in here. The two I had were exact copies of the IIe, all the parts were interchangeable. I gave them and some II+ clones to an American collector about 15 years ago. I’m not a collector so I didn’t have much of an i

 

That's cool that you had a couple IIe clones!!

 

I have never seen one in the flesh, despite being Canadian and growing up around Apple II computers (all models)!

 

Do you happen to remember the brand and model of either?

 

I am curious to look them up...

 

I do remember quite a few Apple II Plus clones back in the day, but clones seemed to dry up by the time the IIe was released, at least in Southern Alberta...

 

Greg

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I don’t recall the names of

I don’t recall the names of the IIe clones. I believe I acquired one through an Apple User Group I was part of. At the time people used to bring in hardware they wanted to give away to the meetings. Around 20 years ago a lot of people were leaving the Apple II for newer platforms. The other came with a major car load of Apple II stuff. I remember the trunk, back seat and passenger seat being piled to the ceiling and driving with one hand holding the passenger seat stuff back so it wouldn’t fall onto me. Probably should have gotten a ticket for that.

I ended up with quite a few II+ clones. Aside from the ones I gave away, the rest had to go when I ran into some issues and had to put most of my stuff into storage. In the last 10 years I acquires a couple more. I got rid of the top case and just use them for chip swapping when troubleshooting a II/II+. And I did keep a single Laser 128 in the original box. Don’t remember which model. Been some time since I fired it up.

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