UDG 4 ZXpand / ZXblast

ZX80 / ZX81 hardware and software offered for sale or swapping
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PokeMon
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Re: UDG 4 ZXpand / ZXblast

Post by PokeMon » Thu Aug 31, 2017 9:57 pm

Mine arrived, too. Maybe already yesterday, didn't open my post box yesterday.
Nice looking gadget. 8-)

nollkolltroll
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Re: UDG 4 ZXpand / ZXblast

Post by nollkolltroll » Fri Sep 01, 2017 8:07 am

Andy: a standard Memotech 16k expander should work, right? The address of the UDG char set will have to be different of course.
/Adam

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Andy Rea
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Re: UDG 4 ZXpand / ZXblast

Post by Andy Rea » Fri Sep 01, 2017 8:29 am

I don't know, i think the.memotecs used dynamic memory which means their will be sone sort of refresh mechanism, so it very likely that it won't work with such memory... :cry:

What I can say is that is if a memory expansion can be used for hi-res graphics then it is likely to work with the UDG board.

Regards Andy
Last edited by Andy Rea on Fri Sep 01, 2017 12:30 pm, edited 1 time in total.
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

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1024MAK
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Location: Looking forward to summer in Somerset, UK...

Re: UDG 4 ZXpand / ZXblast

Post by 1024MAK » Fri Sep 01, 2017 12:01 pm

The 16k byte Memotech RAM packs use both the Z80 refresh cycle and the normal memory cycles for DRAM refresh.
See this thread ;-)

Mark

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Andy Rea
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Re: UDG 4 ZXpand / ZXblast

Post by Andy Rea » Thu Sep 21, 2017 9:22 pm

Bump - listed 10 more boards for sale.

https://www.sellmyretro.com/offer/detai ... pand-28480

regards Andy
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

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siggi
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Re: UDG 4 ZXpand / ZXblast

Post by siggi » Wed Nov 08, 2017 3:48 pm

Andy Rea wrote:
Thu Aug 24, 2017 7:15 pm
A new plug in board that allows the use of external WRX enabled memory
Hi Andy.
I have got a new (old :mrgreen: ) Zeddy, having an external 64KByte-Ram of unknown type (probably no WRX). Do you think that it is possible to use your interface (maybe after an update to make also WRX in a "standard" external ram) for that Zeddy?

http://forum.tlienhard.com/phpBB3/viewt ... 907#p32866

Regards
Siggi
My ZX81 web-server: online since 2007
http://zx81-siggi.endoftheinternet.org/index.html

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Andy Rea
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Re: UDG 4 ZXpand / ZXblast

Post by Andy Rea » Wed Nov 08, 2017 5:44 pm

Hi Siggi,

As i sure your aware for video patterns to be successfully retrieved from ram ( internal or external ) that ram has to be active during refresh, if that ram is static ram then usually it can be altered ( sometimes extra logic is required ) to be active during the refresh, with dynamic rams it can be much harder to achieve.

The UDG board intercepts the zeddies external address lines ( A0 thru A10) and only during refresh the alternate address is placed on the thru address bus, at all other times the original signal is a pass thru as are all the other signals on the edge connector.

Regards Andy
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

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