Hello! Okay that answers all of the questions I had then. Now you are asking a good one. Now how do you want me to get it to you? I'll certainly be present at VCF East on Saturday of course,is one way. The other is by mail, but that way takes a week to a month and has no support methods. I'll even provide two of them. ----- Gregg C Levine gregg.drwho8@gmail.com "This signature fought the Time Wars, time and again." On Sat, Mar 9, 2024 at 11:37 AM Neil Cherry <ncherry@linuxha.com> wrote:
On 3/9/24 02:19, Gregg Levine via vcf-midatlantic wrote:
Hello! A long since closed shop in Manhattan sold me a collection of items wearing legends for the Atari families of hardware. One such was the MMU for the computers that company made. Running the part number of CO61618 through Google sent me off to a website that presented me with the information regarding what it did. I sent them back a note that the part was in fact a HAL16L8 part, and started off as 99 PAL16L8, (I found out years earlier that after the first 100 part numbers ordered, the company could commision a mask for making them up that way.), any this site, https://www.atarimax.com/jindroush.atari.org/achip.html
provided all of the other information needed to ID the other parts. Except they did not help me to elucidate what the terms on the MMU meant. One of them was the use of PB0 and PB1. Now I know of those from the SY6522 IO chip for the SY6502 CPU.
Would one of you who is more familiar with the way the Atari computers work know if they were using an SY6522 that way?
6522 might work but the Atari's use 6520 (usually). I think I have an 800 with a 6820.
The Atari 800xl/600xl has the ability to map in the Atari BASIC, 64K or RAM and Cartridge. PB0 & PB1 are part of that switching. The memory switching is a bit more complicated than I've described but we have the ability to copy the OS ROM into RAM and modify it. Atari used that to modify the OS to play nice with some older games that expected the older 800 (not XL) OS.
We also take advantage of this for the 256L (and further) RAM upgrade.
BTW, one of my Atari 600xl just blew up that chip. I need to get another or the correct PAL or GAL.
-- Linux Home Automation Neil Cherry kd2zrq@linuxha.com http://www.linuxha.com/ Main site http://linuxha.blogspot.com/ My HA Blog Author of: Linux Smart Homes For Dummies KD2ZRQ