Sinclair ZX80 / ZX81 / Z88 Forums

But this can only be done for internal modifications, as the ULA has no access to any external RAM. The loss of this feature will affect any 128k game that makes use of it. Mark Ok, this makes it clear, altough it's unfortunate and makes the ram expansion project a whole lot more challenging :/ Tha...

Before I explain further, a bit of history and a time line. Sinclair’s engineering staff developed the ZX Spectrum 16k and 48k machine’s based on what they had learned in creating the ZX80 and ZX81. The ZX Spectrum+ is just a 48k board (or a 16k board) in a new case with a slightly better keyboard....

Paul wrote: ↑Wed Jan 09, 2019 3:52 pm Can you please post a photo of YOUR pcb? We would like to see if your upper 32k are socketed or not.

Is this good enough? Took that before the s-video mod in October. If it's not good, I'll pop the Speccy open for a better picture

Careful. Only CPUs, microprocessors and microcontrollers execute assembly code. In programmable logic devices, be they PAL, GAL, CPLD or FPGA devices, what you are actually see is device configuration information. This tells the programmer how to configure the logic gates in the device so that it w...

Hi Mark, While this was true for several years microchip technologies is now producing chips starting with ATF. ATF16V8 for example in DIP, PLCC, SOP... Thanks for that, it seems this is pin compatible with the GALs used in the designs: https://www.mouser.fi/datasheet/2/268/doc0407-1180745.pdf But ...

I presume you mean the original rubber key model? Actually fitting larger capacity DRAM chips is not too much of a problem. The problem is adding the circuitry to provide the bank switching capability, especially if you want it to be configured to be the same as in a ZX Spectrum 128k (Toastrack)/+2...

Thanks for accepting me here. Been tinkering with my zx48k (issue 2) and done the following repairs/upgrades: -caps replaced (also inside psu) -regulator replaced -s-video mod done (replaced rf modulator internals) -new keyboard membrane Now the only thing I want is to expand the ram to (at least) 1...