some great info here from Mike. ---------- Forwarded message ---------- From: Mike Stein <[email protected]> Date: Thu, Feb 26, 2015 at 5:18 PM Subject: Re: The Rex Guy To: Steven Ranft <[email protected]> Cc: Stephen Adolph <[email protected]>
Hi Steve, You're absolutely right that a REX is the way to go. But since you asked, the adapter that Stephen mentioned has several (fixed at assembly time) options: 1 - Just convert non-standard pinout to standard JEDEC, to use a 256Kb (32KB) (E)EPROM in an old M100. 2 - Same as #1, but using a 512Kb (64KB) (E)EPROM with an option ROM image in the upper half. 3 - Same as #2, but without pinout conversion, for use in a 'new' M100. If you have a 'new' M100 with the standard socket you can accomplish #3 with a simple 'shim' socket that goes between the system ROM socket and the EPROM and breaks the chip select connection, replacing it with a diode-and connection (with pull-up) to both the original system and the option ROM select signals and a connection to the '512's uppermost address line. The only added connection to the board is a clip lead to the ROM select at M5 pin 5. Regarding enhancements to M100 vs. 102 or 200, check with Steve and/or Ken; most will work with all three models, and they are all intended to not require any mods to the system board or even opening up the case if at all possible.. The 200 is a somewhat different beast altogether; regarding the M100 vs. 102, they are functionally almost identical, but the 102 is thinner, lighter, and has a different system bus connector (like the 200). For that you give up some flexibility, since all the chips (including the system ROM) are soldered, many of them surface mounted. Why not move this to the mail list; others may be interested as well. m ----- Original Message ----- *From:* Steven Ranft <[email protected]> *To:* Mike Stein <[email protected]> *Cc:* [email protected] *Sent:* Thursday, February 26, 2015 4:14 PM *Subject:* RE: The Rex Guy Hi Mike, Will you please explain or can you direct me to more information on the: "replace system ROM with a larger one". I am fine with any performing any soldering mods but I would prefer to NOT change my hardware much. This machine looks very nice inside, and I would like to keep it mostly original. (Mostly ;-) ... ramblings... I repair medical Imaging equipment and have been soldering since I was 12 (1967). I work out of my home and don't have access to a prom burner. I looked on line to see if I could find one cheap, but nothing under $50 that I would want. I would be better of just getting a REX chip. and get much more capabilities. The product has changed so many times the documents for the REX are difficult to follow. I think a REX in my m100 would allow me to swap out several (3?) different "virtual" option ROMs. It also seems it will fix Y2K and allow me to swap out several "pages" of RAM space, and possibly copy between them? For $60, I should just buy one and then after playing a while I would know what it does. I like to explore my options and get the best one up front. I think I got really lucky with this free m100, but maybe I would be better off buying a 102 or 200 and buying toys for that? Also looked at the NEC PC-8300, I like the look of those cursor keys better. I really haven't DONE anything with the m100 yet except research it's possibilities. Ordered a printer or two... Bought a CMOS battery (but my current one charged up to 4 volts after having it plugged into an AC adapter for a while. Steve Ranft Savage, MN ------------------------------ From: [email protected] To: [email protected]; [email protected] Subject: Re: The Rex Guy Date: Thu, 26 Feb 2015 14:19:44 -0500 Hi Steve, You don't *need* TS-DOS, although it is convenient (especially in ROM); there are alternatives such as the self-installing TEENY which gives you the basic LOAD, SAVE and KILL functions. Re Stephen's "Note, if your M100 is a late model, it might just have a standard *option* rom," I think he meant 'standard *system* ROM'. Your mention of a 3256C07-3J1 suggests that you've already opened it up to look inside and that your M100 is new enough to have a JEDEC-standard socket, in which case a regular 28-pin (E)(EP)ROM will fit without any adapter. Hope you checked the NiCd battery while you had it open. If you are handy with a soldering pencil you can make (or if not, buy) a simple adapter that can replace the system ROM with a larger one and give you TS-DOS (or any option ROM) in ROM as well (no soldering to the M100 required). Which mods are you referring to that require soldering wires in/on the M100? I'm not sure why you think it's "vital" to autostart an option ROM instead of calling it, especially if it's your own; it could presumably insert a hook the first time it's called to do that, and there's also the IPL command which might do what you want. In any case, welcome! Sounds like you're going to have lots of fun. See you on the list, m ----- Original Message ----- *From:* Stephen Adolph <[email protected]> *To:* Steven Ranft <[email protected]> *Cc:* Mike Stein <[email protected]> *Sent:* Thursday, February 26, 2015 12:39 PM *Subject:* Re: The Rex Guy Steve thanks for the great note- first some easy stuff- Mike Stein has developed the thing you want - which is an M100 ROM adapter card. copying Mike here. It will make it easy for you to use an eeprom on your M100. Note, if your M100 is a late model, it might just have a standard option rom. There is a file in my personal folder at club100 to help you understand based on motherboard code which style of rom you have. Second, Main rom replacement is useful here as well. If you were inclined to do the soldering , great. O/W an eeprom is cleaner. Third, To do that sort of a patch to the main rom, you will need some code space. The M100 rom has no real space in it. I developed a reworked set of routines in the main rom to drive the LCD. Basically I reduced some table sizes and freed up 150 bytes or so. That could be where you drop your custom code. * since you are thinking about mods like that, main rom replacement is actually superior, because you can flash upgrade your M100 main rom...no need to burn repeat eeproms. REX won't ever plug into the main rom socket - it is really only for option rom socket. SuperREX (if I ever do it!) will only have the benefit of being a larger flash. I will first make a "flashdrive" function from 1/2 of the 1MB flash chip. Then, for Superrom, I simply expand the size of the flash drive. Don't hold your breath; my pace of innovation is not the quickest. If we ever get in that situation, I'm sure I can work something out as an upgrade price. But I would want the old REX back.. those parts are getting expensive! LAst comment - now that I have implemented the Y2K fix as part of REX Manager, for the typical user there is no real motivation to rework the main rom. cheers, Steve On Thu, Feb 26, 2015 at 11:57 AM, Steven Ranft <[email protected]> wrote: Hi Steve, I want to thank you for all the great work you do for the Model-T community. My brother got a free TRS-80 model 100 a while back and never did anything with it. He gave it to me and I have kind of been bitten by the bug. I wanted to figure out how to put this little wonder through it's paces. I was startled at how big a following this tiny 8 bit laptop had. I found Club 100 first and saw the NADS-BOX, but discovered I would also need TS-DOS. I looked for a work around but decided the easiest way to go was to buy the *REX 100 *ROM. I am going to build a Model-T null modem cable an use that, until I decide I use it enough to make the NADS box upgrade worth it to me. I started checking out the REX 100 and found your site. Your work seems great. I saw the section on MAIN ROM Management and why would you want this? (Who wouldn't) I got to the section on the Hardware Mod and thought no sweat, but that's me, 80% of the users out there DON'T want to open their cases, much less solder wires in there machines. It occurred to me you it might be possible to burn a new 3256C07-3J1 with a good set of improvements. Like the fixes to the M100 ROM and the Y2K fix, but most importantly to add a vital piece of code. Code that checks for the presence of an Option ROM, and a small file in RAM. If there is no Option ROM it would just boot to itself. If there is an Option ROM it check the small file to see what to do. It would also pause just long enough for you to interrupt and let you change the default, in case the Option ROM selected is not booting as it should. Changing the Main ROM to this ROM would make the REX 100 and it's successors a much more appealing option to those that can't solder, or are fearful of opening cases. I am sure there are many technical hurdles to this simple idea (or you would have already done it?) Further research on my part revealed the incompatibility of ROM socket layouts of many of the early M 100s. I saw a picture of a ROM on a socket with many of it's pins bent out and not inserted an a whole bunch of wire-wrap jumpers connecting them to different pins. I am not sure how many you could sell (so it might not be cost effective), but an adapter board that has female connectors to plug the ROM into and traces to reroute the connections to the male pins that plug into the ROM socket would be sweet. A later version of REX could plug right into the Main ROM socket. I have been trying to understand the capabilities the REX will give me on my model 100. The documentation is confusing to me. You have so many "irons in the fire"! I am wondering if I should wait until the Super REX is released? If I purchase the REX now, will there be a discount upgrade price for REX owners? Thanks again, Steve Steve Ranft Savage, MN
