Re: UDG 4 ZXpand / ZXblast
Posted: Thu Aug 31, 2017 10:57 pm
Mine arrived, too. Maybe already yesterday, didn't open my post box yesterday.
Nice looking gadget.
Nice looking gadget.
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UDG 4 ZXpand / ZXblast
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Re: UDG 4 ZXpand / ZXblast
Posted: Fri Sep 01, 2017 9:07 am
Andy: a standard Memotech 16k expander should work, right? The address of the UDG char set will have to be different of course.
Re: UDG 4 ZXpand / ZXblast
Posted: Fri Sep 01, 2017 9:29 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... 
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
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
Re: UDG 4 ZXpand / ZXblast
Posted: Fri Sep 01, 2017 1:01 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
See this thread
Mark
Re: UDG 4 ZXpand / ZXblast
Posted: Thu Sep 21, 2017 10:22 pm
Bump - listed 10 more boards for sale.
https://www.sellmyretro.com/offer/detai ... pand-28480
regards Andy
https://www.sellmyretro.com/offer/detai ... pand-28480
regards Andy
Re: UDG 4 ZXpand / ZXblast
Posted: Wed Nov 08, 2017 4:48 pm
Hi Andy.
I have got a new (old
) 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
Re: UDG 4 ZXpand / ZXblast
Posted: Wed Nov 08, 2017 6:44 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
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