ClausB Posted March 7, 2011 Author Share Posted March 7, 2011 - There can be up to three 64K Mosaic boards installed. This gives up to 144K (192K-48K) extended RAM. One card enables 4 banks, two have 20 banks, three have 36 banks. - Banks are 4K, visible at $C000-$CFFF. - RAM is enabled through an address latch (not data). Writes to $FFC0-$FFE3 enable the bank ($FFC0=bank 0, $FFC1=bank 1, etc), writes to $FFXX not in that range disable the memory. Thanks for the details. Do you know which signals (that are not already on the RAM slots) they take from the motherboard or OS board? I assume A15, A14, RD5, and RD4, but I'm not sure. Is there a signal cable between the three boards or are there config jumpers? Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 10, 2011 Share Posted March 10, 2011 Does anyone have a schematic of the Mosaic 64K Select board? Or the installation instructions with solder connections? Or a good photograph? I'm curious how those work. Ironically, i have been looking for a Mosaic 64K on eBay, so i pre-emptively purchased the installation manual. I'll scan it and post it shortly. Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 10, 2011 Share Posted March 10, 2011 (edited) There was a thread about an Atari 400 with a 64K memory module. 64K Atari 800 There is also a 48K Atari Memory Module from Best Electronics 48K Atari 800 What is the difference between the two boards? Also, why would a ram manufacturer make ram chips that aren't a power of two? There is 64K on that 48K board... Edited March 10, 2011 by A8 Hard Drive Quote Link to comment Share on other sites More sharing options...
sloopy Posted March 10, 2011 Share Posted March 10, 2011 both of those are Atari 48k upgrade boards... they have 64k chips as no one has made 48k chips, and its easier and cheaper (and space, power, etc...), to just use 48k of the 64k, then to have 24 16k chips, or 48 8k chips... sloopy. Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 10, 2011 Share Posted March 10, 2011 Turns out it was a Mosaic 32K board, but here are a few pics anyway. Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 10, 2011 Share Posted March 10, 2011 (edited) Are all Atari 48K boards stamped "64K RAM" on the center of the board? Edited March 10, 2011 by A8 Hard Drive Quote Link to comment Share on other sites More sharing options...
ClausB Posted March 10, 2011 Author Share Posted March 10, 2011 Turns out it was a Mosaic 32K board, but here are a few pics anyway. Is there anything in the instructions about which slot in the 800 the 32K board plugs into, and what boards go in the other slots? Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 11, 2011 Share Posted March 11, 2011 I wonder if the Atari 64K RAM modules can be used the same way an Axlon RAMDisk is used without any hardware modification. ClausB: I will post when I get home. Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 11, 2011 Share Posted March 11, 2011 here are the possible memory configurations for the Mosaic 32K Ram module Quote Link to comment Share on other sites More sharing options...
ClausB Posted March 11, 2011 Author Share Posted March 11, 2011 Thanks! Does the manual describe the "companion" board? I suspect it is a blank board that merely loops back the two select signals S2 and S3 as an 8K board would. Judging from the diagrams, it looks like they understood Atari's RAM selection system and connected pins M and T on their 32K board (as does the BASIC program in the first post). Quote Link to comment Share on other sites More sharing options...
ClausB Posted March 12, 2011 Author Share Posted March 12, 2011 I wonder if the Atari 64K RAM modules can be used the same way an Axlon RAMDisk is used without any hardware modification. No. There are not enough signals on any of the RAM slots to address the whole 64K. The Axlon gets 128K via bank selection and it cannot fill more than 16K of the Atari's address space. Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 12, 2011 Share Posted March 12, 2011 I dont suppose I could pull a chip and replace with a bank selector on the Atari 64K RAM board? So a 64K board would show up as 16k in any slot. 3 boards would be 48K bank selectable to 192K. Quote Link to comment Share on other sites More sharing options...
ClausB Posted March 12, 2011 Author Share Posted March 12, 2011 Bank selection requires a fair bit of circuitry to implement a selection register and to multiplex the additional address lines. I did something similar back in '83, converted an Axlon 32K board to a RAMdisk (see this post). Yes, you could modify a regular 64K board to act like a Mosaic 64K board with its 4K banks, if you had a Mosaic schematic, but it would take more effort than swapping a chip. BTW, what does your Mosaic 32K manual say about the "companion" board? Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 12, 2011 Share Posted March 12, 2011 What kind of RAM for the Atari is this? I've never heard of it. eBay Auction -- Item Number: 390284769754 ClausB: I'll post when I get home. Quote Link to comment Share on other sites More sharing options...
ClausB Posted March 12, 2011 Author Share Posted March 12, 2011 What kind of RAM for the Atari is this? I've never heard of it. The picture shows it has the same ICs as a 32K Axlon Ram-Cram. That in slot 2 with a 16K board in slot 1 will make for a 48K 800. Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 12, 2011 Share Posted March 12, 2011 The instructions are broken into two sections, Atari 400 & Atari 800. The 800 section is first, and consists of two pages. The only other time that "Companion" is mentioned anywhere in the instruction manual is the page before the Memory Configurations page - it says "Installation of the Mosaic 32K ram card and companion board, see the memory configurations page" Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 21, 2011 Share Posted March 21, 2011 On a side note, i was looking at ebay items and found this: eBay Auction -- Item Number: 110656954313 If you have an Atari hardware manual, there is a schematic of the 8K & 16K boards. You could measure the resistance of the boards and make a continuity module. I'm sure it would work just jumpered across as well. Kind of like the continuity modules for RAMBUS, If you've ever seen a RAMBUS system. The older Dell Precision systems had them. Nothing special. Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 26, 2011 Share Posted March 26, 2011 So the EXSEL line is connected to all ram slots, yet it isn't used? Quote Link to comment Share on other sites More sharing options...
+warerat Posted March 26, 2011 Share Posted March 26, 2011 So the EXSEL line is connected to all ram slots, yet it isn't used? EXSEL is only present on the last slot and is used by the Bit-3 and AF80 boards. Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 26, 2011 Share Posted March 26, 2011 Could a memory controller card be created for slot 3 that could use slots 1 & 2 for larger ram modules? Quote Link to comment Share on other sites More sharing options...
ClausB Posted March 26, 2011 Author Share Posted March 26, 2011 Could a memory controller card be created for slot 3 that could use slots 1 & 2 for larger ram modules? Yes, I did that: And RAM slot 3 has a useful signal, -EXSEL, which can disable the OS ROMs and allow RAM above page D8. I modded my 800 to do just that: Posted here Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 26, 2011 Share Posted March 26, 2011 Sorry, I'm still wrapping my brain around this. Im transitioning from an Atari fanboy to actually understanding how this all works. This includes a simultaneous lobotomy involving a crash course in assembly for the 6502 AND learning how digital circuits function beyond logical operations (Vol 4 @ allaboutcircuits.com) Can I convince you to make a more legible schematic of your mod? My end goal is to make two 128k boards for slot one and two. Also how does using EXCEL impact other functions of the A800? Thanks! EDIT: Actually if i could figure out how to use the two Atari 64K ram modules with minimal modding would be great Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 26, 2011 Share Posted March 26, 2011 Here are some scans from the Hardware Manual Quote Link to comment Share on other sites More sharing options...
fibrewire Posted March 26, 2011 Share Posted March 26, 2011 ClausB: Never mind, I figured it out. Do any of you have Atari libraries / projects for use with Eagle Layout Editor? Quote Link to comment Share on other sites More sharing options...
OldAtarian Posted March 28, 2011 Share Posted March 28, 2011 Did the 32k cards (a al 400) work in the 800 as well? (ie have 32k with one card or 48k with 32k+16k) Depends who made it. The Axlon RAM-Cram 32K board could work in a 400 or in slot 2 of an 800, but not in slot 1 (because they did not follow Atari's scheme, as noted in the first post). The Intec 32K board could work in either slot 1 or 2 but not in a 400 (they didn't quite get it either). The Austin Franklin flyer claimed their 32K board worked in either slot 1 or 2 and in a 400 (maybe they got it, though I have never seen one to verify). I don't know about the Best 32K board. No 32K board could work by itself in the 800 because no slot has all the select lines S0, S1, S2, and S3 (without loopbacks or jumper wires). So, all the boards above required another RAM board in the other slot. So you're saying the RAM slot in the 400 is wired differently than the 1st RAM in the 800 since 32k boards will work in that without any other RAM board but not in the 800 without another one? That doesn't make much sense. Wouldn't they have used the same process for wiring up the RAM slots on both machines so as not to complicate production unnecessarily? Quote Link to comment Share on other sites More sharing options...
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