exxos's Atari, Amiga & retro forum

Hi all.

Since I suspect my Dragon 32 to have faulty memory, I've been trying to find the datasheet for the OKI M3732L-20RS, however it seems to be very elusive, and the only image I can find of the pinout suggests that the pinout is identical to the 4164 and 4864 ICs, however whilst there is a standard pinout for these RAM ICs, I want to be 100% sure, and the image, clearly grabbed from an OKI datasheet, is too blurry to confirm the address pin assignments.

I was wondering if anybody here might have a digital copy of the OKI M3732L-20RS datasheet at all?

If not, there are options I can try, like buzzing out the address lines to confirm. I am also wondering if the 74LS244 buffer might be an issue, so I may swap that out as I think I already have spares.

Thanks folks :)

They are 4164 chips which failed testing in either the upper or lower half and sold as a 32Kx1 chip, but the 'L' designation means that only the bottom half is operational. The 'H' variant has the upper half operational.

These same chips are used in ZX Spectrums and the Memotech MTX500 as they were cheaper than other 32Kx1 chips due to the fact that they were "seconds".

stephen_usher wrote: 25 Aug 2022 12:01 They are 4164 chips which failed testing in either the upper or lower half and sold as a 32Kx1 chip, but the 'L' designation means that only the bottom half is operational. The 'H' variant has the upper half operational.

These same chips are used in ZX Spectrums and the Memotech MTX500 as they were cheaper than other 32Kx1 chips due to the fact that they were "seconds".

Ahh, interesting, I didn't realise about the H & L designations, though I did know about the bad chips that only half worked :)

I was going to buy some 4164s, but whilst I was digging around over lunchtime I found some 3764s and tried piggybacking, but it made no difference. I did also swap out the LS244, but no change there either.

I had a look around and did not find anything either.

I guess the only place this information may exist is in old OKI RAM handbook :(

exxos wrote: 25 Aug 2022 14:15 I had a look around and did not find anything either.

I guess the only place this information may exist is in old OKI RAM handbook :(

Yes, these seem to be mythical beasts. You'd think given their age, it'd be quite easy to find, like 4164s & 4864s, but no.

It also seems that 4256s have the same pinout, except pin 1 is A9, but on the 4164/4864s and in fact the 3732, it's just not connected, so I might be able to use some of those as repalcements, though I have now ordered some 4164s and may just go through the process of upgrading to 64k. We'll see.

4164s should JustWork(tm).

stephen_usher wrote: 25 Aug 2022 14:29 4164s should JustWork(tm).

That's what I'm hoping for :)

A bit like the Atari 600XL, the 64s will work and just give 16K available without the addressing mods.

exxos wrote: 25 Aug 2022 14:15 I had a look around and did not find anything either.

I guess the only place this information may exist is in old OKI RAM handbook :(

Yes, you should search for those handbook, sometime you find pdf of them on the net. I had to do that for some Hitachi and Philips memory datasheets (ram or eprom)