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<1234567…34>
  • Alternative chips for upper RAM blockDoes anybody know of a way to use 4464 chips instead of 4164 for the upper RAM block in a 48K machine? If not 4464 then something a little more avai…

    Does anybody know of a way to use 4464 chips instead of 4164 for the upper RAM block in a 48K machine? If not 4464 then something a little more available than the 4164. Winston? Piters??

    TIA
    DEATH DEATH August 2007 Hardware
  • Difficult to find upper RAM fault.I've recently repaired an issue 3B 48K Spectrum that had a tricky to diagnose upper RAM fault, so I thought I'd post a report of what I found here. …

    ... passed from testing lower RAM to upper RAM. Here is an example ... first read from the upper RAM location retrieved the decimal ... . were then established in upper RAM, but the system later ... capture the RAM-FILL routine passing from lower RAM to upper RAM, but ...
    Zorn Zorn April 2012 Hardware
  • ZX Spectrum upper RAM module (4532/4164 replacement)Following the [URL="http://zx.zigg.net/LRR/"]lower RAM replacement module[/URL], there have been quite a lot of requests for something similar for th…

    ... for something similar for the upper 32K RAM in a Spectrum.
    upper RAM module instead or one of ... of trailing wires, so the upper RAM module uses almost the same ... as the lower RAM replacement and emulates dynamic RAM.

    ...
    Zorn Zorn July 2013 Sales
  • Upper RAM replacement module issues with the DivideI got my new upper ram replacement module from Zorn yesterday and seem to be having some issues. When the machine is without the Divide it boots up …

    I got my new upper ram replacement module from Zorn ... . When I put the upper ram chips back in place, ... again.

    The upper ram are not on the "OKI ... that also has the upper ram module be so kind ... attempts DMA to the upper RAM and uses unusual timings ...
    gtsamour gtsamour September 2013 Hardware
  • Issue 2 Upper Ram, Loading & ResettingI have a 48k Issue 2 Speccy and for the life of me can't track down what the problem is with it. I initially thought that some of the uppe ram ic's w…

    ... some of the uppe ram ic's were faulty ... went on to desoldered the upper ram ic's, socketed the ... board and replaced the ram with known good chips. ... replaced all the upper ram with known good ram from another Issue ... cant now be the upper ram as I swapped and ...
    retrogamemart retrogamemart December 2014 Hardware
  • Spectrum 48+ 4S - Upper RAM issue, and now a self-created problem!I recently picked up a known-flaky spectrum off eBay, to have a bit of fun fixing it and reliving youth. It was labelled as 'keyboard duff, shows…

    ... diagnostics said the whole of upper RAM was faulty (check all ICs ... , I've removed all the upper RAM ICs, replaced with sockets and ... .

    Given the lower RAM used to be okay, and ...
    Paulcatchpole Paulcatchpole December 2016 Hardware
  • Lower & upper ram IC's for an issue 3 please.Would any of you great folks have 1 spare lower ram, and 1 spare upper ram IC's you would be willing to sell. I'm fixing up a poorly Spectrum that is…

    ... have 1 spare lower ram, and 1 spare upper ram IC's you ...
    Your Spec-chum Your Spec-chum September 2017 Wanted
  • upper ram tacks / TR4 socket...[url="https://photos.app.goo.gl/MkqzRCuNCV3EPr9E7"]https://photos.app.goo.gl/MkqzRCuNCV3EPr9E7[/url] you can only replace that pesky TR4 so many t…

    ... would just fry the lower ram again .. this is one board ... looks like somebody attacked the upper ram with a black and decker ... .. any sugestions for replacing the upper ram tracks ?
    mark8bit mark8bit September 2020 Hardware
  • Built a ZX Spectrum that works, but can't get the upper RAM to work?Like the title says I finished my Spectrum 3B board, and it boots, but it doesn't see the upper 32k of RAM. When it boots, the lower 16k works f…

    ... doesn't see the upper 32k of RAM.

    When it ... , tells me that lower RAM is good, all upper RAM bad. But the ... all the associated logic, and RAM chips, with no effect. I ... all direct connections between the upper RAM and associated logic, and I ...
    DistantStar001 DistantStar001 June 2022 Hardware
  • TKMEM - the 128K interface for 16K SpectrumsHello all! Here in Brazil, we have made a small production of an interface, totally based on Velesoft?s memory expansion ([url]http://velesoft.speccy…

    ... /> Some ZX Spectrum boards have upper ram chips in sockets then is ... ZX48 without sockets must be disable upper ram 32kB (for example via cut ...
    velesoft velesoft January 2013 Hardware
  • Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…

    ... needs an area in RAM to store return addresses ... will be in the "upper" RAM (if it is a 16k ... not need to use the "upper" RAM. So sometimes the ROM ... copyright display before the "upper" RAM fault causes the CPU to ... br /> Maybe easier to just disable upper RAM ?
    Brian Brian April 2014 Hardware
  • New user with a dead 48k issue 2Hello all I've found my way here from watching some excellent youtube videos by Joulesper Coulomb in an attempt to fix a issue 2 rubber key 48k I bo…

    ... of IC23, a 74LS32) should disable upper RAM, but I have a feeling ... IC in either lower or upper RAM is jamming one of the ...
    balford balford July 2014 Hardware
  • Looking for some 48k RAM (upper 32k bank)Greetings, I was wondering where I could find some upper RAM for a 48k (issue 4A). It's the Texas Instruments TMS4532-20NL4 P8419 (or any compatib…

    Greetings,
    I was wondering where I could find some upper RAM for a 48k (issue 4A).
    It's the Texas Instruments TMS4532-20NL4 P8419 (or any compatible RAM).

    Thanks,
    Thomas
    thomas3120 thomas3120 February 2010 Hardware
  • Replacing Upper RAM in 48KHi Folks Well, my fun continues :) After sorting the display issues with this machine I found I couldn't load software meant for 48K machines. Havin…

    ... here it looks like an upper memory fault.

    Before ...
    spookt spookt July 2012 Hardware
  • POKEs on 128K "upper RAM"?I've been working lately with some 128k games, and I've got this question about RAM in games. I guess most games use RAM pages 5 and 2 to store the …

    ... 've got this question about RAM in games.

    I ... guess most games use RAM pages 5 and 2 to ... the main program, and other RAM pages are used to store ... that needs POKEs placed in RAM pages 1, 3, 4, 6 ...
    Zup Zup October 2013 Games
  • Seriously weird Issue 2 issue... (RAM-related)Hi guys; I have been trying to fix up my Issue 2 and have run across a bizarre issue that I haven't seen elsewhere in the forums. Hopefully one of …

    ... .
    2. MEMCHK returned 32767, upper RAM fault. UPRAM85 returned 93, so ... "black screen and red bars" RAM test appears, after which the ...
    Trafferth Trafferth August 2014 Hardware
  • Upper Memory LinksI've got an 1982 Issue Two Spectrum 48k with an upper RAM fault. I've narrowed down the faulty IC and I'm in the process of removing the 8 IC's, sock…

    ... Two Spectrum 48k with an upper RAM fault. I've narrowed down ...
    retrogamemart retrogamemart September 2014 Hardware
  • ZX81 internal RAM board?Just a quick question to Zorn (amongst others). What would the issues be with fitting one of Zorn's RAM boards into an unexpanded ZX81? Seems to me…

    ... fitting one of Zorn's RAM boards into an unexpanded ZX81 ... a lot of the official RAM pack's internal circuitry is ... fit one - preferably the 32K upper RAM board, 'cos I never had ...
    DEATH DEATH October 2014 Hardware
  • 128K RAM tester as .TAP?I was sure that I've seen a RAM tester that can be loaded with e.g. DivIDE or DivMMC EnJOY! as .TAP. But I can't find it (been searching through the …

    ... that I've seen a RAM tester that can be loaded ... only a small error in upper RAM.

    I have a ...
    bverstee bverstee January 2015 Hardware
  • Upper memory issueZX Spectrum 48K, issue 2, boots fine. Lower RAM OK. When tested with the new test ROM in the Diagboard, for all upper RAM tests "FAIL" is shown. I…

    ... 2, boots fine.
    Lower RAM OK.
    When tested with ... in the Diagboard, for all upper RAM tests "FAIL" is shown.
    RAM, are the voltages:
    4116 ...
    georgedb georgedb September 2016 Hardware
  • Spectrum 48k won't start any software but passes all RAM testsI have a rubber key 48k which will not start any software - it appears to work perfectly right up until the end of the tape and the program would sta…

    ... was a problem with the upper RAM however on running the soak ... minutes. I also performed the RAM test detailed here http://www ... longer or look for non-RAM related issues?
    britain4 britain4 October 2016 Hardware
  • 48K Issue 2 RAM issuesI have 48K issue 2 board (I've checked, the upper memory is present!). It's not very well. I've not attempted to diagnose one before, so please bear …

    ... board (I've checked, the upper memory is present!). It's ... issues are only in the upper RAM as it will actually boot ...
    kurbeco kurbeco August 2019 Hardware
  • zx spectrum display corruption .. with lower ram module installed[img]https://photos.app.goo.gl/Gu6rjC5v21sZxwTX9[/img] [img]https://photos.app.goo.gl/FznVw8SkbbhWn5mh7[/img] another specie question : i have …

    ... video corruption, it has lower ram module fitted.. can get it ... and it shows lower ram as good and upper ram not detected although ... i start digging at the upper ram, or the 4 logic chips ... that drive the upper ram.. i am presuming that one ...
    mark8bit mark8bit January 2021 Hardware
  • Spectrum RAM Paks...This jogged my memory (excuse the pun!!) : [url]http://cgi.ebay.co.uk/CURRAH-32K-RAM-PACK-BOXED-SINCLAIR-ZX-SPECTRUM_W0QQitemZ150057889352QQihZ005QQ…

    ... put one of these 32K Ram packs on a 48K Spectrum ... /> both the internal upper 32k and the RAM pack will be mapped ... the Spectrums edge connector to disable internal RAM (unlike the ZX81), they ...
    MikeW MikeW November 2006 Sinclair Miscellaneous
  • Black paper, white border. Ram fault?We have a speccy that wont work properly. When we power it up, we get white border around a black screen. We swapped the rom and ula with a working o…

    ... could be the Z80, lower RAM or upper RAM.

    The best ... the voltages on the 4116 RAM first because you can immediately ... of the 74LS157 multiplexers to disable the upper 32K (I can't ...
    Winston Winston December 2006 Hardware
  • Dead Spectrum +Hi all, I've recently dug out my old Spectrum + with the idea of repairing it. When I last looked at it, when I was much younger, I was soldering a …

    ... chip enable logic for the upper RAM (I think it's ... ) first for testing upper RAM, since this will disable it. This will ... in the cases where upper RAM is merely returning bad ... common failure mode of RAM is to just return ... least test all of RAM and the ULA in ...
    Winston Winston March 2007 Hardware
  • Someone can help me to fix my Zx Spectrum?I did a video about the startup: [url]http://dl.dropbox.com/u/1566495/ZXSPECTRUM03.mp4[/url] I have replaced the ULA with a working one (same proble…

    ... ;431155]
    If the ram is faulty and if I ... upper RAM bank (the 32K bank).
    This method will disable the upper ... still be in the lower RAM bank (the 16K bank ... ).
    Lower RAM cannot be disabled, as the ... if any of the RAM chips in the lower ...
    Pilsener Pilsener March 2010 Hardware
  • ZX Spectrum + Issue 6A Repair attemptHello everybody! I got ZX Spectrum + which doesnt work properly. On power up I can see color mosaic, then paper goes black and i can see thin red ba…

    ... upper RAM chips aren't socketed? In that case, easiest way to disable ... always a prime suspect (especially RAM, sometimes ROM), but could also ... . Let's hope disabling the upper RAM provides some clues...
    RetroTechie RetroTechie July 2010 Hardware
  • TKMEM - the 128K interface for 16K SpectrumsHello all! Here in Brazil, we have made a small production of an interface, totally based on Velesoft?s memory expansion ([url]http://velesoft.speccy…

    [QUOTE=Crisis;672363]so now there is beside the 48k upgrade kit a 128k upgrade interface, wow ![/QUOTE]

    It's not perfect, but works very well.
    And you must disable the 32k upper ram. :D
    Turrican Turrican December 2012 Hardware
  • TKMEM - the 128K interface for 16K SpectrumsHello all! Here in Brazil, we have made a small production of an interface, totally based on Velesoft?s memory expansion ([url]http://velesoft.speccy…

    You can disable the 32k of upper RAM by a wire or jumper ...
    flopping flopping January 2013 Hardware
<1234567…34>

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Related Threads

  • Alternative chips for upper RAM blockDoes anybody know of a way to use 4464 chips instead of 4164 for the upper RAM block in a 48K machine? If not 4464 then something a little more avai…
  • Looking for some 48k RAM (upper 32k bank)Greetings,<br /> I was wondering where I could find some upper RAM for a 48k (issue 4A).<br /> It's the Texas Instruments TMS4532-20NL4 P8419 (or …
  • Difficult to find upper RAM fault.I've recently repaired an issue 3B 48K Spectrum that had a tricky to diagnose upper RAM fault, so I thought I'd post a report of what I found here.<b…
  • Inefficient code in ROM, from ram-check to RAM-DONEHere is the inefficient code:<br /> <br /> [CODE]<br /> ;; ram-check<br /> L11DA: LD H,D ; Transfer the top value to the HL registe…
  • Replacing Upper RAM in 48KHi Folks<br /> <br /> Well, my fun continues :) After sorting the display issues with this machine I found I couldn't load software meant for 48K mac…
  • ZX Spectrum upper RAM module (4532/4164 replacement)Following the [URL="http://zx.zigg.net/LRR/"]lower RAM replacement module[/URL], there have been quite a lot of requests for something similar for th…
  • Upper RAM replacement module issues with the DivideI got my new upper ram replacement module from Zorn yesterday and seem to be having some issues.<br /> <br /> When the machine is without the Divide …
  • POKEs on 128K "upper RAM"?I've been working lately with some 128k games, and I've got this question about RAM in games.<br /> <br /> I guess most games use RAM pages 5 and 2 t…
  • Issue 2 Upper Ram, Loading & ResettingI have a 48k Issue 2 Speccy and for the life of me can't track down what the problem is with it. I initially thought that some of the uppe ram ic's w…
  • Spectrum 48+ 4S - Upper RAM issue, and now a self-created problem!I recently picked up a known-flaky spectrum off eBay, to have a bit of fun fixing it and reliving youth. <br /> <br /> It was labelled as 'keyboard…

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