Allison wrote: Ahh, not had experience of that one before (I don't think anyway). 177x was pretty common in machines over here, and the 8271 gets used in a lot of Acorn hardware which is why I'm used to it... I'm not hugely worried about GCR formats (I gather the ACT Sirius uses GCR too) at this stage, although I suppose if it's just reasonably simple logic then I can keep in mind - ability to add the relevant daughtercard to this planned board at a later date, say. I've not given thought to hard sectored disks at the moment - I'd expect that the common FDC chips don't support them at all, so it's a different project entirely... Well part of the plan is to raid the junk pile and at least put some of it to use, which would likely mean a 2732 EPROM for on-board ROM and 6116 SRAM chips for memory - latter subject to power requirements and board space though. I know I've got quite a few of them kicking around, but they're physically large chips and not *that* big a capacity (8kbit or 16kbit I think, going from my hazy memory...) Of course I've got a boatload of various DRAM chips though, so if the Z80 does provide pretty much all the refresh needed then maybe that's a better bet. Ahh, thanks for that list. We've got a truckload of S100 hardware at the museum, so there's definitely a possibility there - I'm just not sure without checking what FDC cards we have. I don't know what spare ROM boards we'll have either (my programmer won't do three-rail devices, so I'd need a board that'd take slightly newer EPROMs...) Agreed :) I can't see parallel being complex though; I guess there's just handshaking protocol to design on top of hooking the chip itself up (unless I got for individual ICs to do the parallel interface), but it doesn't need to be anything complicated. I've got a few weeks until I'm back in the UK, so it gives me something to ponder over in the meantime though :) cheers Jules