Subject: Re: USR quad modems... (ontopic - really!) From: ard at p850ug1.demon.co.uk (Tony Duell) Date: Wed, 16 Aug 2006 23:35:41 +0100 (BST) To: cctalk at classiccmp.org Unless either (a) the USB part number is just their code for a standard device (HP were fond of doing this...), or (b) you can disable the internal mask ROM and run it from external program store, say by changing the state of a pin. Without knowing more about the device I can't possibly know if either of these is the case. The CoCo 3 is designed round a custom chip called GIME (Graphics, Interrupts, Memroy Enhancement). It handles all the video side, the memory mamangement (remmber the 6809 can only directly address 64K), etc. Said chip outputs a 9 bit multiplexed address (designed to link to the 9 addres pins on 256K bit DRAMs), and the DRAM timing signals. It also expects 16 bit wide memory IIRC. It's probably possible to add external circuitry to turn that back into a normal 18 bit address and hang SRAM off it, but I think it's more work than finding some 41256s...

As I commented last night, citric acid is ideal for cleaning up battery corrosion from calles with alkaline electrolyte (NiCds, alkaline primary cells, etc).