Recent content by -N2

Whee 64MB! https://www.ebay.com/itm/116328614196?

mostly latches or bus muxes I presume?

With 5-volt CPLD chips becoming harder to source, how many 74-series chips would it take to build this DRAM interface circuit?

This might be doable with a large bank switchable memory card,

Mixing legacy 5-volt systems with the newer low-voltage stuff is when hobby projects become less enjoyable.

With an additional latch, the A15 line might be used to toggle between two independent banks. Where one set of bits from RegB is used to control the lower 32K and another for the upper 32K. I am not aware of any existing code that could use all that, but it seems technically feasible. Who knows...

Yes that last bit about RegB on A8-A15. Thinking about it some more, A0-A7 + 4 LSB bits from RegB during Ras A8-A14 + 4 MSB bits from RegB with A15 placed as the MSB during CAS is a clean way to handle the different SIMM sizes in software. With anything less than a 16MB SIMM the A15 pin isn't a...

Would it be possible to cheat by asserting the high byte during an I/O write? Well perhaps I should first ask how you are converting the 15-bit linear address into the two-part Ras/Cas addressing for the SIMM30 memory. Is it as simple as using the first 12 Least significant bits for the first...

Heh I made an 80-pin carrier board for an Arduino Mega2560 if you'd like to try it. I'll have to dig up the design files; I think I included a SIP header for this uSD card adapter https://www.pololu.com/product/2587 I recall the purpose of this abomination was to have enough GPIO to monitor all...

I wonder if a super crude hack of flip/flopping the 8th bit clocked from the LSB would work to interleave the refresh cycles.

Can your board work with the Z80Ctrl board? The ctrl board has an AVR Microcontroller on it to act as a pony processor to load SRAM on a companion support board. Such a model enables a system with only RAM and no ROM. Is there enough space in the CPLD to fill the bottom 32KB of address space...

To be frank I trust the sellers on AliExpress more than any eBay vendor I have ever dealt with.

Not everyone can source the specified PLCC-packaged z80 CPU.

the 80 pin interface appears to have these signals, https://smallcomputercentral.com/wp-content/uploads/2023/03/rcbus-specification-v1.0-2023-03-17.pdf

I was unaware this specific version of the chip supports the PC ISA bus, who knows a PC AT bus CPU card might be nice.