Sinclair ZX80 / ZX81 / Z88 Forums

McKlaud wrote: ↑Fri Mar 09, 2018 11:54 pm Andy, I am glad reading your post. You are Master Yoda of ZX81 ULA, I am just newbie in this world. BTW Could you correct pictures, I can't see them.

see if it images show now

regards

Images now showing for me

Mark

Andy Rea wrote: ↑Sat Mar 10, 2018 12:13 am

McKlaud wrote: ↑Fri Mar 09, 2018 11:54 pm Andy, I am glad reading your post. You are Master Yoda of ZX81 ULA, I am just newbie in this world. BTW Could you correct pictures, I can't see them.

see if it images show now

regards

Thanks a lot, now they are perfectly visible

Estimated power usage...really low?

In my case the CPLD is not even warm. The hottest part in my testing board is the ROM chip now. The power consumption is roughly 250mA, but I have also got a 16KB SRAM chip on this board. I think I could go even lower if the 7805 were replaced with any decent DC-DC converter.

First "K" seen on the screen, but some issues with stability and timings.

@McKlaud and Andy: NICE!!! Especially Andy's 45-degree placement of the CPLD is likely how I'd have done it myself.

McKlaud wrote:The power consumption is roughly 250mA, but I have also got a 16KB SRAM chip on this board. I think I could go even lower if the 7805 were replaced with any decent DC-DC converter.

Indeed. My ZX81 pulls around 800 mW, that is DC-DC converter included. Some 600 mW (120 mA @5V) if powered with 5V directly. CMOS Z80 and CPLD macrocells in low-power mode are the biggest quick/easy savings afaik.

Top job Claudius, it's a very rewarding feeling when you get an image for the first time.

@retrotechie, cheers man, the driving factors for that kind of placement was size wanted it basically the same size as the socket and i really wanted all 40 pins through hole instead of the central ones been smd It does mean that i lose 4 pins as the corner ones are so close to the through holes that they are doubled up. But plenty of pins anyway.

Regards Andy

Well done to all concerned.

Look forward to seeing these on Sell My Retro.