From: "Andreas Magenheimer" Subject: additional ramdisk info (part 2) Date: יום שישי 17 מאי 2002 20:40 Hello Folks, yet another ramdisk info text, for those that are interested or for the collectors. -Andreas. -------------------------------------------------------------------------------- NEWELL 256k to RAMBO XL Switch By Craig Goranson Version 1.0 October 17,1990 Version 1.1 May 7,1991 This is instructions on how to install a switch, with some hardware, to give your Newell Industries memory expansion board 100% RAMBO XL compatibility. I. Why I built it. (this is just some background) When I decided to upgrade my 800XL to 256k I chose the Newell Industries upgrade. It is a very well thought out upgrade and I have been happy with it and its performance. Unfortunately the Newell upgrade and the popular Rambo XL/CLaus Bucholz upgrades are incompatible. They use different bank selection technics and locations that means software written for the Rambo XL will not run on the Newell upgrade. The two main differences between the upgrades is the fact that the Newell does not allow you to bank select the main memory while the Rambo does, and the fact that they went with different memory maps of the banks. Because of this I could not run such fine programs as SNAPSHOT and MTOS3. There has been a modification out for some time that added a switch that rectified the bank switching incompatibilities so the Newell could use the same bank select sequence as the rambo XL, but it did not fix the problem that the Newell does not allow you to select the main banks. So I decided to sit down and fix it so the Newell could be switched to 100% Rambo compatible mode. The next section is how the upgrade works. You can skip it if you just want to get down to the nitty gritty. II. How it works The problem arises with how the two upgrades handles bits 5 and 6 of PORTB. Bits 5 & 6 can equal from 0 to 3 and select one of the 4, 64k segments of the 256k chips. Bits 2 & 3 of PORTB then select 1 of the 4, 16k banks of the 64K subdivision. (4*16k=64K,64K*4=256k) The following is a table of the values for bits 5 & 6 on the Newell and Rambo boards and which 64k bank they select. |-----------------------------------------| |B|B| Newell Board | Rambo Board | |5|6| 64k bank | 64k bank | |-|-|-------------------|-----------------| |0|0| enhanced bank | main 64k bank | * |1|0| protected | enhanced bank | |0|1| enhanced bank | enhanced bank | * |1|1| enhanced bank | enhanced bank | |-----------------------------------------| In the above table you will notice the "protected" bank in the Newell table. This is the number that would select the main banks of memory if they were not blocked out. Instead of the Newell switching in the main banks of memory it just switches in the same banks as if bits 5 & 6 were both 1's. If you ran a program that expected to be using a machine with a RamboXL upgrade, it will seem to work but the mirror effect of the one bank being switched in as two different banks will destroy data. (The RD.COM file from Sparta Dos takes advantage of this fact to tell if you have a RAMBO or not.) A simple fix to this problem is to invert the BIT 5 before it reaches the Newell board. This is the fix that was given to us by Wess Newell. This fixes the mirror bank problem, and RD.COM and other software will run, the bit inversion juggles the banks so they are in the right place. But the Newell upgrade still protects the main bank of memory. SO software written for the Rambo that needs to access the main banks through the $4000- $8000 window still will not work. (Major Crash!!) My solution is fairly simple to build it you are good will a soldering iron and are fairly patient. What my modification basically does is invert bit 5, bypass a NOR gate, and invert a bit that was going through the NOR gate. It to lengthy to explain the nitty gritty so I will leave it up to you to figure it out if you really want to. You don't need to understand how it works to install it, the main thing is that it works. Anyway after this modification is installed you will have a switch to change between 100% Rambo mode and 100% Newell mode. The best of both worlds. III. Building the Newell/RAMBO switch Parts list. 1 74ls14 inverter (or 7414,7404,74ls04, doesn't matter.) 1 DPDT switch for mounting on case a fairly good amount of wire You will also need a soldering iron, solder, a small awl or screw driver to pry up a pin, and a steady hand. (and prayer if you are religious.) And a desoldering device such as a suction device or de-soldering braid. Assembling it: 1. remove the top, and shielding from you computer to you are looking down at the Newell board. ( I hope you know how to do that.) 2. Locate the 7402 or 74ls02 chip on you Newell Board. It should be on the left side, second from the bottom. It is labeled U5 on my board. 3. Locate pin 1 of the U5 chip and desolder it. 4. Carefully bend up pin one and clip it off leaving enough room to solder a wire on to it. 5. Clean up the solder pad that pin one was pried out of, then solder one end of a wire to it. 6. Orient the DPDT switch so you are looking at the back of it. I will refer to the pins by the letters as follows in the diagram below. The "*" sign designates a pin on the back of the switch. a* d* b* e* c* f* 7. Solder the other end of the wire, that is attached to the solder pad, to pin "b" of the switch. 8. Now desolder the wire that goes from the Newell board to pin 15 of the PIA chip, from the PIA. (the pia chip is labeled U23 on the computer board) Then attach the end of the wire to pin "e" of the switch. (This allows the re-routing of the BIT 5 of PORTB) 9. Now solder a wire from pin 1 of the U5 chip to pin "a" of the switch. (pin one is the one you bent up earlier.) 10. Now get you 74ls14 (or equivalent) and trim all the pins except 3,8,16. Leaving enough room to tack solder wires on to the trimmed pins. 11. Next solder a wire from pin 4 of the 74ls14 to pin "c" of the switch. 12. Solder a wire from pin 1 of the 74ls14 to pin"d" of the switch 13. Now carefully place the 74ls14 chip over U5 (74ls02) on your newell board. Then solder pins 3,8,16 to the corresponding pins on U5. The chip should piggy back nicely on the U5 chip and the only pins of the 74ls14 chip that should touch pins on the 74ls02(U5) is 3,8,16. 14. Desolder the wires (from the pia) that go from the Newell upgrade board to pins 12 & 13 of the PIA chip. Then solder the wire that went to pin 12 to pin 13. And solder the wire that went to pin 13 to pin 12. (you are just swapping the wires to put the banks in the right order) 15. Last but not least solder a wire from pin 15 of the PIA to pin"d" on the switch. (there should now be two connections on pin "d" of the switch) 16. Congrats!!! You made it. You now have a switch that can be mounted were you want, that gives you full RamboXL compatibility at a flip of the switch and allows you to switch back to Newell mode. I also recommend that you install the switch described in you newell instalation manual that allows the Antic chip to follow bank selecting. This will give full compatibility with about every program. Any input is welcome, as I can be reached on by BBS or genie. This is the first revision of this modifications so I would appreciate any notifications of errors in this document. (except grammar and spelling) --- Revisions: v. 1.0 The document as I originally wrote in back when I made the modifications to my computer. v. 1.1 revised on may 6, 1991. I had left out step #14 in which you swap the wires going to pins 12 & 13. - Craig Goranson - ------------------------------------------------------------------------------- EoE or EoF.