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The new Superfo cloneHi In the spanish forum speccy.org some guys and me have optimized the superfo clon to have less ICs. The actual design has 39 ICs versus the 45 ICs…
... the Z80 to access the upper ram without collision. But when the ... design improvement, if it were not for:
1. Cost ... be the better design choice, not knowing about the floating bus ... is coupled to the video ram through resistors, in this undecoded ... -
maximum addressable RAM for a Z80 using bank switching?What is the maximum addressable RAM for a Z80 using bank switching? The Enterprise64 home computer could address up to 4MB, is this the limit for a …
... 256 banks of 32K SRAM (upper RAM).
Never made more than ... software using it, it's not very useful.
It could ... as a removable storage interface, RAM with battery or ROM cartridges ... -
ZX8401 / PCF1306P / Amstrad 40058 for 48K and 128KZX8401 = PCF1306P = Amstrad 40058, let's get started with that. These chips are used as surrogates. Most of us might think those chips were only use…
... So that chip is for upper memory adressing, check out ... that because of the ram paging at the 128K, ... with paging, leaving the upper memory logic intact, like ... of the 4164/4532 upper ram chips, so Sinclair could ... all upper ram chips we order fully work, why not use ... -
Issue 3 board... How to resurrect?Dear Everyone, Now I have a working 48k Issue 3, a sort of working Speccy+ (still having problems with the keyboard, more of that in another post) a…
... quite common for a faulty upper RAM IC to interfere on the ... 16K model. Sometimes a failed RAM IC develops a short between ... rail. This can often be detected by making resistance measurements: With ... set of measurements. Remove any RAM IC that gives an usually ... -
Issue 3 board... How to resurrect?Dear Everyone, Now I have a working 48k Issue 3, a sort of working Speccy+ (still having problems with the keyboard, more of that in another post) a…
... with the lower RAM chips, and sometimes with the upper RAM chips. Occasionally ... I find a faulty ULA, but that is not ... ZTX650 transistor if it was not fitted with the necessary mods ... -
Cascading transistorsMiguel (mcleod_ideafix) alerted me on an aspect of a design I'm working on where I am cascading transistors, which may give problems. This is the par…
... stabilize, but it is not the only element that has ... the image. ROM and upper RAM are also available at this ... supply rails to feed lower RAM. The DC-DC converter ... from nowhere because lower RAM won't be ready ... rail, ULA and lower RAM are ready and working, the ... -
ZX Spectrum 48K working as 16K from factoryGood morning I Have a Zx Spectrum 48k working as 16K , it came like this from factory. What can i do to solve this , and put it to work as 48K? Wha…
... 48K Spectrum with faulty upper RAM, but the initial RAM test routine passes ... a few bytes) of the upper RAM. All sorts of strange things ... each time. The result might not always be the same.
ZX Spectrum 48K working as 16K from factoryGood morning I Have a Zx Spectrum 48k working as 16K , it came like this from factory. What can i do to solve this , and put it to work as 48K? Wha…
... the /RAS signals for the upper RAM and so the ROM code ... only the lower 16K of RAM. The output of the voltage ... obtain 5V. Take great care not to let your jumper wire ... touch anything else." The RAM test program would probably then ...Corrupt paper on zx spectrum 48kHi. When I power up my spectrum (issue 3) I get the light grey border, but the paper is black and it switches between thin red vertical lines and thi…
... of two groups of RAM chips.
The ... so called lower RAM (used for the screen ... sometimes called the screen RAM) is made from eight ...
The so called upper RAM also uses eight DRAM chips ...
The two types are not interchangeable.
The ...Barn find #4I think this is some sort of backup device. Its got "007" on the motherboard and the mice have chewed the buttons. Will do a little research later in…
... MC-routine must run in RAM. The paging circumstances (an address ... found by testing. That would not be too much of a ... copy content of ROM to upper RAM and then "emulate" NMI jump ...When is a 16k not a 16k ?Can anyone explain what this machine is supposed to be ? Speccy with a 16K sticker on the base. Doing a peek 23733 returns 255 so a 48K ? Opened …
... use OKI upper RAM (soldered in place), but I've not seen it ...When is a 16k not a 16k ?Can anyone explain what this machine is supposed to be ? Speccy with a 16K sticker on the base. Doing a peek 23733 returns 255 so a 48K ? Opened …
... -RAMT. This is not true. If the upper RAM is absent or completely ... 16K model and it is not possible to tell which from ... that faulty, but somewhat functioning RAM is present in the computer.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 …
... transistor inverter circuit. I would not have thought that this alone ... />
And anyway, /MREQ is not routed to the DRAM sockets ... is what the "ZX Spectrum Upper RAM Module" plugs into. The module ... then supplies /RAS to the RAM).
What chip is ...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 …
... inverter circuit. I would not have thought that this ... /> And anyway, /MREQ is not routed to the DRAM sockets ... what the "ZX Spectrum Upper RAM Module" plugs into. The ... then supplies /RAS to the RAM).
... for T3. The Z80 was not designed for that.
SoftPLAY: Use the PLAY command from 48 BASICNow you don't need 128 BASIC to use the [B]PLAY[/B] command. Just use [B]PRINT #8;[/B] instead. [url]https://dl.dropboxusercontent.com/u/15659782/So…
... can compile code to ZX ram. Final version can be from ... #C000. If UDG "U" is not detected then jump to address #000E ... . If UDG "U" is detected then jump to your play ...SoftPLAY: Use the PLAY command from 48 BASICNow you don't need 128 BASIC to use the [B]PLAY[/B] command. Just use [B]PRINT #8;[/B] instead. [url]https://dl.dropboxusercontent.com/u/15659782/So…
... can compile code to ZX ram. Final version can be ... #C000. If UDG "U" is not detected then jump to address #000E ... . If UDG "U" is detected then jump to your play ... you need to call in RAM is 0xF740. CH-ADD ... handler though as I'm not familiar with the divIDE ...First time capacitor replacementHi, I have an Issue 2 board, that i wish to start with recapping as advised on here, as they look to be all original. (Same with V3 board, but going…
... typical pattern of a lower RAM failure any more.
upper RAM area.
You could ... as an alternative if its not throwing out the right volts ...First time capacitor replacementHi, I have an Issue 2 board, that i wish to start with recapping as advised on here, as they look to be all original. (Same with V3 board, but going…
... another board, although again not socketed and also not working, so wont ... /> How do I disable the upper ram? Cut tracks? Ill take a ...Issue 3 board with strange piggy-back boardIn case you are interested. I?ve never seen something like this before. I have an Issue 3 board here. When I opened the case and found a strange pig…
... . It has on bank 0 not the diagnostic rom code but ... lower Ram is broken or the 12V and -5V are not available ... recognized that there is no Ram test using this Rom. Is ... price which works and has upper ram and may be address logic ...Video failureHi i cant find the failure of my spectrum 48k issue 4a, i thought it was ic6 or ic13 but the memory seem to have the right values. When i turn it on…
... I'll go for faulty upper RAM disrupting the initialisation.
... /RAS signals for the upper RAM and so the ROM code ... the lower 16K of RAM. The output of the ... 5V. Take great care not to let your jumper wire ... , I'd try removing the upper RAM ICs.
...Issue 3 board with strange piggy-back boardIn case you are interested. I?ve never seen something like this before. I have an Issue 3 board here. When I opened the case and found a strange pig…
... times) to indicate the lower ram failure
- After that all ... me this means that all RAM chips are faulty which is ... - 26 and all upper Ram chips
128K Ram test ROM
Or do I totally not understand the output from test ...Black Screen Spectrum 48kWas working ok, it came to me in a Fuller FDS keyboard, I had a nose inside and found a floating power lead connected to the keyboard, I removed that…
... but I'd suspect faulty upper RAM. Try the following to ... a 16K Spectrum. If not and in the absence of ... necessary to remove all the upper RAM ICs.
" ... /RAS signals for the upper RAM and so the ROM code ... 5V. Take great care not to let your jumper wire ...Black Screen Spectrum 48kWas working ok, it came to me in a Fuller FDS keyboard, I had a nose inside and found a floating power lead connected to the keyboard, I removed that…
... but I'd suspect faulty upper RAM. Try the following to ... a 16K Spectrum. If not and in the absence of ... necessary to remove all the upper RAM ICs.
" ... /RAS signals for the upper RAM and so the ROM code ... 5V. Take great care not to let your jumper wire ...Black Screen Spectrum 48kWas working ok, it came to me in a Fuller FDS keyboard, I had a nose inside and found a floating power lead connected to the keyboard, I removed that…
... but I'd suspect faulty upper RAM. Try the following to ... a 16K Spectrum. If not and in the absence of ... necessary to remove all the upper RAM ICs.
" ... /RAS signals for the upper RAM and so the ROM code ... 5V. Take great care not to let your jumper wire ...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 …
... several Spectrums, all with the upper RAM module installed. I haven't ... the potential problem, even if not much can be done about ... can be used with the upper RAM module.Born again Speccy user with problemsHello all, Firstly I'd like to say a big hello - this is my first post! When I was 8 or 9 or so my dad bought a ZX Spectrum 48K and a whole bunch o…
... very first byte of upper RAM and sometimes that is ... if it detects all upper RAM is faulty). However, ... the cause of you not being able to load ... failure to load is not supplying a strong enough ... .
Other not altogether uncommon problems that can ...Another "untested" dead spectrum...Hi, I'm looking for some suggestions on a faulty Spectrum I have picked up. I'll need to wait until tomorrow before posting pics, but the screen is …
... power supply would be an upper RAM IC interfering on the data ... fault. Sometimes it can be detected by examining the waveforms on ...Spectrum Not Responding to Keyboard InputHello, sorry if this thread is not in the correct place, This is my first post and I'm not sure where to post this type of thread. :lol: Anyway, I r…
... would indicate a possible lower RAM failure (8 chips at the ... CPU, or in the lower/upper RAM that is holding a data ... behaviour like the above when upper RAM is not behaving itself (machine boots ...Spectrum Not Responding to Keyboard InputHello, sorry if this thread is not in the correct place, This is my first post and I'm not sure where to post this type of thread. :lol: Anyway, I r…
... a way you can isolate upper RAM from the system to ... problem to one of 8 upper memory chips.
... the CAS signal from the upper memory bank. Mcleod_ideafix suggested ... this, except the "upper" RAM chips are disabled, not isolated. They will still ...Plea for new hardwareI'm posting this as a poll as I want to judge if I'm a solo loon going on about this, or if people really are interested in either of the following S…
... lower to the upper 8K half of the contended RAM then that ... listening for writes to the upper RAM and replicating them in the ... 'd have to sacrifice your upper memory to exploit it.
not to at least try!
