RiscPC VRAM dies. But it's often just the PCB - it gets damaged with battery corrosion right at the edge connector and can be very tricky to fix.
"So I made a new one", as he says...
I've only built this as a 1MB module so far, as I'm still waiting for a batch of RAMs on the slow boat from China. And I mislaid the inductors (uses ickle 1206 ones, as from my A540 RAM project), so this is built with 0Rs in their place. But it works - using RAMs lifted from a dead original so far.
It's "just" a direct implementation of the official Acorn part - entering the schematic to Altium, then doing my own layout. And boy was the layout tricky - keeping it to 4 layers and in the available board outline was one of the trickier things I've routed.
As usual with my Acorn stuff, it's all opensource in GitHub : https://github.com/IJeffray/RiscPC_VRAM
This is the first step of a 3 step project - the next step is to create it using 4x16bit RAMs rather than 8x8bit - I have to do all that routing again!![:?]( "Confused")
I'll have a number of these for sale eventually, but if you do build your own (not fully tested yet!), remember to order a 1.2mm thick PCB. I also opted for the 2U gold finish at JLCPCB - for the connector fingers. And they'll also hit you for full 4-wire Kelvin test as I used 0.2mm drill on 0.4mm vias.
"So I made a new one", as he says...
I've only built this as a 1MB module so far, as I'm still waiting for a batch of RAMs on the slow boat from China. And I mislaid the inductors (uses ickle 1206 ones, as from my A540 RAM project), so this is built with 0Rs in their place. But it works - using RAMs lifted from a dead original so far.
It's "just" a direct implementation of the official Acorn part - entering the schematic to Altium, then doing my own layout. And boy was the layout tricky - keeping it to 4 layers and in the available board outline was one of the trickier things I've routed.
As usual with my Acorn stuff, it's all opensource in GitHub : https://github.com/IJeffray/RiscPC_VRAM
This is the first step of a 3 step project - the next step is to create it using 4x16bit RAMs rather than 8x8bit - I have to do all that routing again!
I'll have a number of these for sale eventually, but if you do build your own (not fully tested yet!), remember to order a 1.2mm thick PCB. I also opted for the 2U gold finish at JLCPCB - for the connector fingers. And they'll also hit you for full 4-wire Kelvin test as I used 0.2mm drill on 0.4mm vias.
Statistics: Posted by IanJeffray — Fri Dec 20, 2024 4:19 pm