8x ramdisk

A project log for vector-06c mini

A 50% size replica of my favourite 8-bit computer

svofskisvofski 04/19/2024 at 20:080 Comments

One expansion that's a must for every Vector-06c is a 256K ramdisk, colloquially known as kvaz (quasi-disk). It's in fact a ram expansion which presents itself as 4 64K pages of stack-addressable ram. Part of each 64K page can also be mapped as a 16K window in screen space area. A common improvement to this disk is a so-called Barkar Extension, which allows opening extra 2x 8K windows into 64K address space, thus making 128K of 256K directly addressable.

A common v06c would have one such attachment. However with some craftsmanship, two kvazas can be used with one machine. They would map to the same address space and be configured via separate I/O ports. However, there exists one test program that can simultaneously probe 8x kvaz, making up a total of 2MB of RAM. Unfortunately I don't know of any software that would make use of such a vast amount of memory, except for the test itself. Take note that even just zeroing 2M is a pretty serious undertaking for a 8080-based computer.

With 32x2Mbit PSRAM available on the FPGA chip it would be a crime not to support this feature (and with a lot of room to spare), so here we go.