How to perform a Timex Sinclair 1000 internal memory upgrade?

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Kahenraz
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How to perform a Timex Sinclair 1000 internal memory upgrade?

Post by Kahenraz » Mon Feb 10, 2020 4:16 pm

I bought a 2k Timex Sinclair 1000. Are there any guides on how to upgrade its internal memory? I'd like to upgrade it enough to be able to get high res graphics.

I bought some 8-bit 32k SRAM chips in DIP packages. What size chips do I need for various upgrade sizes; 16k, 48k, 56k?
Last edited by Kahenraz on Tue Feb 11, 2020 6:44 am, edited 1 time in total.

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1024MAK
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Re: How to perform a Timex Sinclair 1000 internal memory upgrade?

Post by 1024MAK » Mon Feb 10, 2020 11:57 pm

Hello and welcome :D

There is a welcome area if you want to tell other members something about yourself ;)

The TS1000 is very similar to a ZX81 issue 3 board.
If you browse or search the forums for ZX81 RAM upgrade or ZX81 memory upgrade, there are numerous others who have done this, and links and guides on how to do it.

The type of RAM is Static RAM (SRAM). This comes in various sizes, but now only 8K byte, 32K byte and 128K byte chips are easy to get hold of (you need the type that works on a 5V supply, often said to be TTL compatible).

Not many ZX81 / TS1000 programs / games / applications need more than 16K. So the most common internal RAM upgrade is to use a 32K byte SRAM chip, but configure the modification so that the Z80’s CPU can only see 16K bytes of the new RAM chip. Why you ask, well because of the way that the machine works. Making full use of the new RAM chip means more control circuitry is needed.

Mark

Kahenraz
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Re: How to perform a Timex Sinclair 1000 internal memory upgrade?

Post by Kahenraz » Tue Feb 11, 2020 9:47 am

I'm having trouble following what I'm reading online. Can an internal modification be performed to increase the available SRAM to its maximum of 56kB (+ 8kB ROM for 64k)?

I'm finding documents indicating how to upgrade the internal RAM to 16kB or 32kB but then I only find information about 64kB when also mentioning RAMPACKs.

I'm also reading that any RAM expansion module will disable the internal SRAM. So will I need to make or modify an external RAM pack to go beyond 32kB?

Sources (16k):

http://blog.tynemouthsoftware.co.uk/201 ... k-ram.html
https://www.sinclairzxworld.com/viewtop ... f=7&t=3045

Sources (32k):

Internal 32K-RAM for ZX81
Expand your memory up to 32K
WRX1K V1.0 1996 - HIRES ON A 1K ZX81
Both require SRAM for the hires screen and this means that (unmodified) 16K-64K DRAM packs are not suitable. While a few people may have installed 8K or 32K SRAM chips in their ZX81...
Sources (64k):

A VERSATILE 64K RAMPACK FOR THE ZX81
It is quite possible to utilize the full 64K of RAM on a ZX81. ... The first RAM chip is normal static RAM ... A Lithium coin cell provides battery backup power to the second 32K RAM chip to make the contents non-volatile when the ZX81 power is off.
viewtopic.php?p=29663#p29663

This is the only source I found which talks about internal RAM larger than 32kB. What is the usage difference between the "ROM Patch" schematic and the "Barebones" schematic? There are some issues indicated by other forum members. Are there better schematics or other instructions to follow for this mod?

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1024MAK
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Re: How to perform a Timex Sinclair 1000 internal memory upgrade?

Post by 1024MAK » Tue Feb 11, 2020 10:19 am

The ULA only provides very basic ‘partial’ decoding of the memory. To increase the RAM above 16Kmeans additional logic (chips) are required. In theory there is no reason why the internal RAM cannot be expanded to 56K bytes. However, not many people have done this. Hence it may be difficult to find any information on doing this.

With any internal RAM upgrade, the existing 2K byte SRAM chip is removed. Then a suitable socket is fitted. Modifications are required to either the tracks on the PCB or by bending the pins of the SRAM chip(s) where wires are then soldered.

Mark

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Paul
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Re: How to perform a Timex Sinclair 1000 internal memory upgrade?

Post by Paul » Tue Feb 11, 2020 3:49 pm

A working schematic can be found on the german Forum.
ZX-TEAM 56KSchematic
corresponding text can be translated by google translate.
In case of questions, don't hesitate to ask
Kind regards
Paul
In theory, there is no difference between theory and practice. But, in practice, there is.

tdg8934
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Re: How to perform a Timex Sinclair 1000 internal memory upgrade?

Post by tdg8934 » Wed Feb 12, 2020 9:28 pm

Before you go through the trouble of updating your TS1000 to 32KB of ram, you might want to consider trying to purchase if available, a ZXPand+ which already has the 32KB ram AND has a SD card support for storing your *.P program files (no more tape drive). Just my 2 cents!

Tim

Kahenraz
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Re: How to perform a Timex Sinclair 1000 internal memory upgrade?

Post by Kahenraz » Thu Feb 13, 2020 2:27 am

ZXPand+ is out of stock. :)

Mustermann
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Re: How to perform a Timex Sinclair 1000 internal memory upgrade?

Post by Mustermann » Sat Feb 22, 2020 10:48 am

There are a couple of solutions out there how to expand ZX81(that is nearly identical if I am right) to more than 32k.

Form my point of view you need some decisions first:

- Are you interested in High Res
- If yes, are you fine with WRX High Res only(possible with 1 RAM chip) or do you like to implement UDG as well(need 2 RAM chips)
- Do you like to create ROM overlay(need 2 RAM chips)
- Are you interested in battery backup for RAM(helpfull to protect character-tables or drivers in 8k-16k area)

There is no need to remove existing RAM chip but it need to be disabled.
To avoid bending chip pins a socket can be placed in between.
My personal favorite is removing existing ram, soldering a high quality socket in the size of the new RAM into the board and do all rewiring at that level.


Max
ZX81 issue 1 near to original state
ZX81 issue 1 under construction (64k internal ram)
Minstrel 3 ZX81 clone 64k with battery backup, UDG and CHR$128 enabled

Kahenraz
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Re: How to perform a Timex Sinclair 1000 internal memory upgrade?

Post by Kahenraz » Sun Feb 23, 2020 7:34 pm

I am interested in both WRX for high-res as well as UDG.

Battery backed ram sounds interesting, and I do have some tiny LiPo batteries which might be perfect.

I ordered some 32k SRAM chips over a month ago from China. Still waiting for them to slow-boat over here. Zzzz.

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