Mine arrived, too. Maybe already yesterday, didn't open my post box yesterday.
Nice looking gadget.
UDG 4 ZXpand / ZXblast
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- Posts: 330
- Joined: Sat Sep 27, 2014 8:02 pm
- Location: Stockholm, Sweden
Re: UDG 4 ZXpand / ZXblast
Andy: a standard Memotech 16k expander should work, right? The address of the UDG char set will have to be different of course.
/Adam
Re: UDG 4 ZXpand / ZXblast
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
Last edited by Andy Rea on Fri Sep 01, 2017 1:30 pm, edited 1 time in total.
what's that Smell.... smells like fresh flux and solder fumes...
- 1024MAK
- Posts: 5165
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: UDG 4 ZXpand / ZXblast
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
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer being good this year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer being good this year.
Re: UDG 4 ZXpand / ZXblast
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
what's that Smell.... smells like fresh flux and solder fumes...
Re: UDG 4 ZXpand / ZXblast
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
My ZX81 web-server: online since 2007, running since dec. 2020 using ZeddyNet hardware
http://zx81.ddns.net/ZxTeaM
http://zx81.ddns.net/ZxTeaM
Re: UDG 4 ZXpand / ZXblast
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
what's that Smell.... smells like fresh flux and solder fumes...