fjkraan
Experienced Member
A project more than three years in the making, and finally something to show.
The Non-Intelligent RAN Disk is a 120k Byte battery back-upped RAM disk for the Epson PX-4 and PX-8.
Unlike the Intelligent RAM Disk, which is (Z80) CPU based and works via commands, the Non-Intelligent
RAM Disk is I/O-register based. The only complicating feature is that the lower address byte has a
auto-increment function, implemented in a custom Epson chip.
At one time, a 512k Byte RAM Disk was created, lacking the auto-increment feature
(https://electrickery.nl/comp/px8/512kByteRAMDisk.html). This meant the
OS-ROM had to be patched, both for the larger size and the increment feature.
The current implementation works with the standard OS-ROM, and uses two GALs for addressing,
timing and the auto-increment. The board is prepared to connect three additional 128k Byte RAM
chips to enlarge the RAM Disk size. This requires patching CP/M at startup and might be done with
some User-BIOS code.
The RAM-Disk is currently only tested for the PX-4, but should also work for the PX-8.
The project is still very incomplete, it will take some time to complete testing and sweeping some of the
more embarrassing mistakes under the carpet.
GALs are vintage, but still available cheap in small quantities. 128k Byte NVRAM could solve the
battery problem but those are still surprisingly expensive (for a few).
Greetings,
Fred Jan
The Non-Intelligent RAN Disk is a 120k Byte battery back-upped RAM disk for the Epson PX-4 and PX-8.
Unlike the Intelligent RAM Disk, which is (Z80) CPU based and works via commands, the Non-Intelligent
RAM Disk is I/O-register based. The only complicating feature is that the lower address byte has a
auto-increment function, implemented in a custom Epson chip.
At one time, a 512k Byte RAM Disk was created, lacking the auto-increment feature
(https://electrickery.nl/comp/px8/512kByteRAMDisk.html). This meant the
OS-ROM had to be patched, both for the larger size and the increment feature.
The current implementation works with the standard OS-ROM, and uses two GALs for addressing,
timing and the auto-increment. The board is prepared to connect three additional 128k Byte RAM
chips to enlarge the RAM Disk size. This requires patching CP/M at startup and might be done with
some User-BIOS code.
The RAM-Disk is currently only tested for the PX-4, but should also work for the PX-8.
The project is still very incomplete, it will take some time to complete testing and sweeping some of the
more embarrassing mistakes under the carpet.
GALs are vintage, but still available cheap in small quantities. 128k Byte NVRAM could solve the
battery problem but those are still surprisingly expensive (for a few).
Greetings,
Fred Jan
