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<1234567…34>
  • 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. …

    ... section named RAM-FILL loops over all possible RAM addresses, from high ... passed from testing lower RAM to upper RAM. Here is an ... first read from the upper RAM location retrieved the decimal ... the RAM-FILL routine passing from lower RAM to upper RAM, but ...
    Zorn Zorn April 2012 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.

    RAM is good, all upper RAM bad. But ... the associated logic, and RAM chips, with no effect ... direct connections between the upper RAM and associated logic, ... PEEKed at the 8 addresses above 23733 (from ...
    DistantStar001 DistantStar001 June 2022 Hardware
  • 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
  • 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
  • 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
  • It's a trap!So I got a CPLD (not the eventual one I want to use for the ethernet project - rather, one I actually have here and now, an XC9536 in a PLCC44). And…

    ... instruction fetches at the following addresses

    - 0x0000 - only when ... , by fooling it into thinking upper RAM is being accessed. (This will ...
    Winston Winston December 2007 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
  • Interesting 48K failureI thought I'd recount a failure I've not seen mentioned before that I saw tonight while fixing a 48K issue 6 board. The background: The initial fail…

    ... :
    1. A fault in upper RAM causing incorrect instructions to get ... odd numbered I/O port addresses. This was never fixed inside ...
    Winston Winston December 2013 Hardware
  • 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
  • Method to read byte as binary string rather than dec?Hi all Am fiddling around with the screen buffer and have written a routine to scan the screenbuffer into upper ram and then write it back in upside…

    ... to scan the screenbuffer into upper ram and then write it back ... and write all the start addresses...

    Hope this helps ...
    miskox miskox February 2006 Sinclair Basic
  • Noob to Z80 needing +3 helpI'm quite new to z80 programming, but i'm attempting to write some kind of windowing system that will run alongside BASIC on my +3 with Kempston mous…

    ... if DOS is active, RAM Page 7 is here instead ... and copy it into the upper RAM bank, and go back ... to dos (repeat until upper bank is 'full' / my ... dos routines from the upper bank (as ram page 7 is ... (almost) real time which addresses my symbols are at, that ...
    rbsfou rbsfou August 2009 Development
  • Requesting a little help to identify the purpose of this 'add-on' to my Issue 2Hi everyone First of all it's my first post here so please go easy on me! I'm grateful to be accepted into your fine little club :smile: I probabl…

    ... the 8 lower RAM chips and the 8 upper ones. The -5v ... it, thereby doing a rudimentary ram test. I assembled it to ... leads me to believe that upper ram is definitely suspect. Unfortunately I ... or whether it gives random addresses. If it gives the same ...
    cmonkey cmonkey October 2011 Hardware
  • Rubber 48k troublesHi. I've just got a 48k to add my collection, but it seems doesn't working well. The computer starts ups finely, but it doesn't load the games. So fa…

    One of your upper RAM chips almost certainly has a ... , but you must set all addresses in one go and then ...
    Spirantho Spirantho January 2012 Hardware
  • Rubber 48k troublesHi. I've just got a 48k to add my collection, but it seems doesn't working well. The computer starts ups finely, but it doesn't load the games. So fa…

    ... =Spirantho;597771]One of your upper RAM chips almost certainly has a ... , but you must set all addresses in one go and then ...
    Spectrum Spectrum January 2012 Hardware
  • Spectrum 48K - upper memory MIAI have recently acquired a ZX Spectrum which, according to the sticker on the bottom, should be a 48K model. It's an Issue 3 board, with upper memory…

    ... value to all possible RAM addresses. Then, from the ... be set-up accordingly at addresses below this.
    < ... first address in the upper RAM during this test it ... that go to the upper RAM or one of ... control and addresses lines connected to the upper RAM, to see ...
    Zorn Zorn February 2012 Hardware
  • Issue 2 headache!Ive got an issue 2 here that firstly had a blown regulator (fixed), now its reading as a 16k machine (its fully populated), ive replaced and socketed…

    ... problem was, as suspected, faulty upper RAM.

    Note that the ... working address found by the RAM test routine. So, for what ... you should be testing at addresses *above* the highest good one ... try to identify the faulty RAM IC.
    Zorn Zorn August 2012 Hardware
  • Spectrum 16K Issue 3Hi! I just received a Spectrum 16K, which turns out to be an Issue 3. Is it really that rare? If not, I?d like to upgrade it to 48K. There are 12 em…

    ... a random value in the upper 32K (say 60000) and PEEK ... 0 to 255) to upper RAM in consecutive addresses, then read the values ... ? :) ) - modify values in upper RAM and see if other RAM addresses change when you ...
    Spirantho Spirantho November 2012 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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