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FarmerPotato

Geneve Clock Chip MM58274 source?

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I'm looking for a source of clock chip MM58274. It was used in the Geneve 9640.   It has 4-bit registers, mapped with 4 address bits.

 

Here is the thread I found with some history:  

 

 

 

I looked for MM58274 on aliexpress, and it goes for $7. I looked at several sellers that use the same photo and price.

 

$7

image.png.2b54512babc7a49552af7783925f599b.png

 

I found this for $1 that is possibly fake. It doesn't have the Microchip logo, but has a sane date code. It could be a remark (laser on new markings because old ones are faded), a fake remark (dummy chip, usually with impossible date code), or else Microchip used another fab in '95.

 

$1 for real?

image.png.9ee52735733d1b51fb5ea0bbfc7e85d7.png

 

 

Mine in the Geneve 9640 has the logo and '87 date code.

 

Any opinions on whether that is real or fake? I can try one sample for $6 shipped, might be worth a try.

eBay is a mixed bag but there are a lot of photos there. One from '99 has the Microchip logo.

 

Or another source?

 

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I found an Intersil chip that is listed as a suitable substitute. My usual sources don't have any MM58274s in stock.

cdp68hc68t1e.pdf

 

Note: this chip is a functional equivalent, not a drop-in replacement.

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44 minutes ago, Ksarul said:

I found an Intersil chip that is listed as a suitable substitute. My usual sources don't have any MM58274s in stock.

cdp68hc68t1e.pdf 141.84 kB · 1 download

 

Note: this chip is a functional equivalent, not a drop-in replacement.

 

 

Octopart shows a bunch of those 

but mostly for $6-$12, except one Harris brand copy is at Rochester for $0.86

 


Hmm, SPI is sorta ok. It means I have to memory-map it through the FPGA. Maybe have the FPGA shadow it continuously every 0.05s.
But with that technique, I could use any $1 SPI chip and make it look compatible.

 

MC68HC68T1 is another that is similarly costly.
 

I might go for some legit-looking eBay 58274 chips and test them.

 

Thanks for locating that alternative!

 

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Hey, here is a copy of an Application Note for the 58274 under a friendly document name!

 

https://cdn.preterhuman.net/texts/computing/msx/Geneve_Clock_App_Notes_AN-365.pdf

 

There's a nice personal collection of documents there. Probably all in wht already but...

Holy crap, it's a mixture of TI-99/4A documents and MSX, including service manuals for the CX5M.

I am having a feast... Thanks, clock chip!

 

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I'm pissed. I had a few from last year when I found some and now I'm not sure where they are. I'll keep looking..

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18 minutes ago, GDMike said:

I'm pissed. I had a few from last year when I found some and now I'm not sure where they are. I'll keep looking..

The 58274? did you have a good source?

 

 

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eBay suggested a Seiko/Epson 72423.

 

It looks similar: 16 registers, BCD, but the registers are in different addresses. No tenths of seconds. Not quite compatible.
These are still stocked by Mouser, for $8, but old ones are out there.

 

Modern Seiko-Epson RTCs are all I2C or SPI with the exception of:

 

RTC7301DG.  The RTC7301SF comes with a temperature sensor! Still around $7.

 

https://www5.epsondevice.com/en/products/rtc/rtc7301sf.html

 

Registers match 72423, ie offset from where MDOS looks.

Not cheap either. Except 72421 used.
 

 

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By coincidence I was looking a RTC chips a few weeks ago. Looking at some old boards, I arrived at the MM58174 as a chip that was period correct and has direct links to very first RTC chips to appear on the market in the 1970's (the OKI M5832).

For an 8 bit variant have a look at the MM58167.


A third choice could be an early serial chip, the NEC uPD4990. This can maybe be coerced to act like a CRU interface chip.

 

I think all are still available on eBay, but I have no direct buying experiences for any of the above.

 

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1 hour ago, FarmerPotato said:

The 58274? did you have a good source?

 

 

I'll go back over my order form and try to locate where I got them.

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3 hours ago, FarmerPotato said:

 

https://cdn.preterhuman.net/texts/computing/msx/Geneve_Clock_App_Notes_AN-365.pdf

 

There's a nice personal collection of documents there. Probably all in wht already but...

Holy crap, it's a mixture of TI-99/4A documents and MSX, including service manuals for the CX5M.

I am having a feast... Thanks, clock chip!

 

I wonder where this mishmash came from.  I see files in there that I put together for distribution, such as the HFDC schematics, that are not in their associated ZIP file.  I also see at least one file of mine that I do not recall ever releasing, although I suppose it could have been scraped from an email.  Interesting.

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If you could use it let me know, I also have like, 200 ea 32768 crystals..lol also new.

I can throw it all in an envelope out to ya.

 

 

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