exxos's Atari, Amiga & retro forum

PhilC wrote: 05 Jun 2025 10:24 Not sure if that means my card doesn't do interleaving either?

I'd effectively be redoing the layout of most of the card and layout from scratch, and I'm thinking of using two 1MB chips (reducing chip count by two), but 5v 1MB DRAMs seem hard to find. 256 x 16 chips seem much more common and easy to find (leaving the chip count the same).

To make use of one of the key features of the ET4000/W32i for high resolutions, the memory bank interleaving that is reflected in the "i" suffix, it is important to have two banks of 32 bits each, so your 1-megabyte DRAM chips would need to be 256K x 32.
Two 512Kx16 chips will not allow interleaving - if they are supported at all. I can find 256K x 16 5V chips a dime a dozen, and if I am really desperate to get some, I will buy a "for parts only" untested very early PCI graphics cards on ebay (be careful to not get EDO, see below), which usually contains 2 to 8 of these chips. On the other hand, I have no idea whether I have a single 5V FPM 256K x 32 at all.

For bank interleaving on the ET4000/W32i, it is of utmost importance to not use EDO, but FPM only, because the bank interleaving requires that the "inactive" bank stops sending data as soon as the /CAS signal gets de-asserted, otherwise, both banks will conflict. The key point of EDO is that it allows to pipeline two stages of RAM reading inside the RAM chip, allowing similar performance with a single bank to what the W32i achieves using two banks. As EDO RAM was not common when the ET4000/W32i was designed, Tseng used bank interleaving an incompatible way to achieve the same result - they pipeline the memory access by interleaving data transfer between two different chips. So this adds another constraint to your search: You would need 256K x 32, 5V, FPM RAM. While there definitely are x32 RAM chips, I tend to see them only at 3.3V, and with an EDO or SDRAM interface. That's technology that is way newer than the ET4000/W32i.

PhilC wrote: 05 Jun 2025 10:04 @mrbombermillzy I'll have a go with that later on. I've not tried joystick in the Raven yet though :lol:

PhilC wrote: 05 Jun 2025 10:24 @mrbombermillzy I tried it and I just get a busy mouse pointer as below, not crashed though as the mouse still moves

mrbombermillzy wrote: 05 Jun 2025 15:07

PhilC wrote: 05 Jun 2025 10:04 @mrbombermillzy I'll have a go with that later on. I've not tried joystick in the Raven yet though :lol:

I think I put keyboard arrow key support in there too. :)

PhilC wrote: 05 Jun 2025 10:24 @mrbombermillzy I tried it and I just get a busy mouse pointer as below, not crashed though as the mouse still moves

Sorry Phil.

I should have given you the later non hardwired screen address version.

mrbombermillzy wrote: 05 Jun 2025 16:35 Actually Phil, bit of a glaring oversight (on my part), but unless the Raven has a blitter it wont work. Sorry. :(

I can maybe code a non-blitter version at some point and send it over to you.