Sinclair ZX80 / ZX81 / Z88 Forums

Posted: **Mon Oct 09, 2017 4:28 pm**

I just found myself bidding on and winning an untested 32K Memopak (secretly hoping it would not work so it would form a very cool and numerically accurate home for my ‘spand) which turns out to be working, although no significant tests done yet.

I opened the case to see which caps may need replacing and noted a few things which surprised me:-

No nice little switch box (unlike my 16K)
No obvious caps to replace
Lots of nice little spaces ready for additional chips to maybe make it up to 64K?

6F18720A-02C3-4667-97BD-B8AE7B95D8AD.jpeg: (645.82 KiB) Downloaded 507 times

And a 7805 regulator (UA7805UC)!

95DF1CA2-D74C-4566-8098-877C3414ED1C.jpeg: (1.74 MiB) Downloaded 507 times

Just out of curiosity is it possible to expand one of these to 64k?

Lardo

Posted: **Mon Oct 09, 2017 7:44 pm**

Dunno. I too have various Memotech expansions including a fair number of "untested" 16k byte expansions, all bought only for the cases, but all of which work (so for the time being, they are safe...). I also have at least one of the higher capacity memory expansions, but I forget now which

I'm busy this week, but will see if I can find time to have a look next week to see which ones I have.

Mark

Posted: **Tue Oct 10, 2017 9:01 am**

In this old thread you will find a lot of information (and pics) of Memotech modules (incl. ram):

viewtopic.php?f=7&t=865&p=8583&hilit=memotech+ram#p8583

Regards
Siggi

Posted: **Tue Oct 10, 2017 10:34 am**

Lardo Boffin wrote: ↑Mon Oct 09, 2017 4:28 pm Lots of nice little spaces ready for additional chips to maybe make it up to 64K?

The board itself may probably also be used for 64K ram modules. But AFAIK the Memotech rams contain a programmed chip (PROM?) for address decoding. So you would need to get the appropriate PROM for the 64K board....

Siggi

Posted: **Tue Oct 10, 2017 11:55 am**

siggi wrote: ↑Tue Oct 10, 2017 10:34 am
Lardo Boffin wrote: ↑Mon Oct 09, 2017 4:28 pm Lots of nice little spaces ready for additional chips to maybe make it up to 64K?
The board itself may probably also be used for 64K ram modules. But AFAIK the Memotech rams contain a programmed chip (PROM?) for address decoding. So you would need to get the appropriate PROM for the 64K board....

Siggi

Thanks. It was just idle curiosity - I have no idea what I would do with 64k on a zeddy anyway!

Posted: **Tue Oct 10, 2017 12:08 pm**

I have a lot of ideas:
run ZeddyNet and its applications:
- use ram at 8-16K for ZeddyNet system variables
- run ZeddyFox or NFM (network filemanager) in ram 32K-48K
- load/save a BASIC-Program (using ZeddyFox or NFM) in ram 16-32K

Or use IRC-ANSI.P (ZX81 chat program) at 16-32K, having its ZeddyNet system variables at 8-16K and its HIRES image above 48K

Siggi

Posted: **Tue Oct 10, 2017 12:21 pm**

Lardo Boffin wrote: ↑Tue Oct 10, 2017 11:55 am Thanks. It was just idle curiosity - I have no idea what I would do with 64k on a zeddy anyway!

I have no version of Hot Z (Hi-Z) which runs without 48K.

Posted: **Tue Oct 10, 2017 12:34 pm**

Here's a photo of my 64k.
For reference of the necessary bridge connections.

IMG_20171010_123223.jpg: (3.29 MiB) Downloaded 405 times

Posted: **Tue Oct 10, 2017 12:35 pm**

Lardo Boffin wrote: ↑Tue Oct 10, 2017 11:55 am I have no idea what I would do with 64k on a zeddy anyway!

Or use ZXPAINT do draw (and print) some nice HIRES pictures: has its HIRES image at 8K-16K and needs ram above 32K to keep a second HIRES picture available:

viewtopic.php?f=6&t=260&p=1924&hilit=ZxPaint#p1910

Siggi

Posted: **Tue Oct 10, 2017 3:57 pm**

Looks like maybe all is needed is 4 pole dip-switch, chips (from another 16k, 32k?), some caps

List: classiccmp
Subject: Re: OKI M3732L-20RS ram datasheet?
From: Chris Elmquist <chrise () pobox ! com>
Date: 2008-12-03 13:22:59
Message-ID: 20081203132259.GJ5784 () n0jcf ! net
[Download message RAW]

On Saturday (11/29/2008 at 12:44PM +0000), Pete Turnbull wrote:
> On 28/11/2008 21:41, Chris Elmquist wrote:
>> Does anyone have a datasheet for these parts?
>
>> Although, by the part number alone, one might suspect they are a
>> 32Kx1 device possibly...
>
> I don't have a datasheet but I found several equivalences in a Toshiba 1982
> databook. MSM37xx designates MOS DRAM, MSM21xx is MOS static RAM, MSM51xx
> is CMOS SRAM, and MSM27xx is EPROM. I found the more of the same in an NEC
> databook, but of all the memory databooks I've got, the 1982 Toshiba is the
> only one listing any MSM37xx devices.
>
> OKI MSM3764-xx is an exact equivalent of a 4164, and the 2-digit suffix
> gives the speed in tens of ns. I'd guess that an MSM3732-20 is 32Kx1,
> 200ns access time, and likely consists of an MSM3764 with one half disabled
> or dysfunctional. If so, the 'RS' may signify which half works.

Thank you Peter. That pretty much confirms my suspicions. Can't for the
life of me remember what piece of gear would have used them. Must have
been some memory expansion board for a PC that I had at one time. That's
all I can figure...

Chris

--
Chris Elmquist
mailto:chrise@pobox.com

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Memotech Memopak 32k

Memotech Memopak 32k

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