Unless you write your own operating system, *expanding* RAM linearly without bank switching is not "rare", it's not possible; the CPU can only address 64K, of which the lower 32K is occupied by the system ROM (OS, BASIC,other built-in apps) and a few K of RAM at the top are reserved for system variables.
On Wed, Nov 20, 2024 at 9:36 PM Chris Kmiec <[email protected]> wrote: > Thanks everyone, looks like the LCD is what it is, and anything beyond 32k > RAM is very rare and not really worth it since REX can just switch out the > whole 32k. Time to dive in and start playing with what I have! > > Chris > > On Wed, Nov 20, 2024 at 4:18 PM Brian K. White <[email protected]> > wrote: > >> On 11/20/24 08:19, Chris Kmiec wrote: >> > >> > Hmm, I don’t see that feature in the specs for REX#. It has 1mb of >> Flash >> > memory for storing ROM images and can backup and restore the ram, but I >> > don’t see and RAM on REX that would allow me to max out Tandy’s onboard >> RAM. >> >> There's a few different things to explain here... >> >> The machine can only address up to 32k at a time, so in one sense there >> is no ram expansion beyond filling all 4 possible 8k sockets inside. You >> have a few different options for that. GGLabs sells a module called >> M10-RAM that you can buy. They have a site for the info but the actual >> buy link is on ebay or tindie etc. Otherwise you can build your own by >> following https://github.com/bkw777/Model_T_RAM >> >> (Apologies but this mail will end up having a few links to things from >> me on github since I've been playing with several forms of ram & rom >> addons for the 100-200 the last few years) >> >> There have been several forms of ram expansion that connect to the >> system bus and work by containing multiple banks of 32k and you have a >> software method to switch from one bank to another. You can only access >> the contents of a single bank at any one time. It's like unplugging all >> your chips and putting other chips in. I think the PG Design ones driver >> software might have some feature to be able to move a file from one bank >> to another, so there was some just barely form of access to the other >> banks. No one makes those currently but years ago Steve Adolf made >> something called QUAD which replicated the PG Design, and more recently >> I replicated & updated QUAD to make reQUAD >> https://github.com/bkw777/reQUAD >> No one makes it for sale but you can buy all the parts and build one >> yourself or find someone to do it for you. >> >> >> All 3 types of REX, (REX Classic, REX#, REXCPM) include a feature to do >> full backups & restore of the 32k internal ram. It's not quite the >> one-button instant swap like with the ram expansions, but just about. >> It's only a few presses to go into REXMGR and do a backup & then a >> restore. In fact I think he might have even streamlined that operation >> in the latest version for REX#. I know he did add some overwrite >> protection to avoid accidental deletes or overwrites. So in the end, >> it's functionally almost the same as having a ram expansion. It's just >> that underneath what's really happening is you are dumping the current >> ram out to a chunk of flash and then restoring some other chunk of flash >> over the ram. The actual ram expansions only gave you essentially the >> same outward functionality, just a little faster. >> >> REXCPM is a special case in that it also actually replaces your internal >> ram with it's own 32k. So if you have less than 32k, a REXCPM would give >> you 32k. >> >> If Steve can't sell you a REX# or REXCPM at the moment, there is an >> option to build your own REX Classic. >> https://github.com/bkw777/REX_Classic >> >> Not ram but probably the more practical way to have more room to work is >> disk space. The most practical answer for that is a Backpack. >> https://www.soigeneris.com/universal-backpack-drive >> >> I have something you can build called PDDuino which actually predates >> backpack, but backpack is far more feature rich and polished. (From what >> I can tell. I have not used one because since I want to work on the >> fully open source option that does the same thing, I don't want to ever >> be accused of even seeing the firmware in the backpack.) >> https://github.com/bkw777/PDDuino >> >> Basically the idea is 99% of the hardware is just an off-the-shelf >> Adafruit Feather or Teensy dev board and you just plug it in to a little >> serial port adapter board. It has a rechargeable lithium cell you >> recharge by usb, or you can just run on usb alone, or you can even run >> on power tapped from the BCR port. >> >> I've also made a version of a kind of ram disk that seems like at one >> time a few different people all made versions of essentially the same >> thing. It's a very neat little circuit where basically it's nothing but >> an address latch, a binary counter, and some ram, and that ends up >> emulating a spinning disk. The device only supports 2 functions, select >> a block address, and read/write a byte. Each time you select a block >> address, the binary counter is also reset to 0. Each time your read or >> write a byte, the binary counter is also advanced by 1. A block has 1024 >> bytes. So You select say block 40, then just read 1024 times to read the >> entire block. Like picking a track number and reading the track. >> >> https://github.com/bkw777/NODE_DATAPAC?tab=readme-ov-file#minindp >> >> But this needs to connect to the system bus and that's inconvenient on a >> Model 100 because it would need to be on a cable extending out to the >> back of the machine. You can actually use the Model 100 adapter portion >> of a DVI (Disk/Video Interface) cable for this. >> But really it's only good on a 102 or 200 where it just plugs directly >> onto the back of the machine. >> >> And what you get is disk space not ram. You could get disk space in a >> generally more convenient and flexible form from Backpack or PDDuino >> because those use the TPDD protocol, for which there are several bits of >> compatible software and hardware. IE, you have a choice of a few >> different kinds of TPDD driver software to run on the 100, and then the >> drive can also be used by other machines. the TANDY WP-2 has built-in >> tpdd support in it's firmware. You can connect a real TPDD drive or a >> backpack/pdduino to a PC and there are several softwares to access the >> drive or emulate a drive in any os, since the connection is just rs-232 >> and the protocol is known. >> >> While the RAMPAC-alikes there is no pc software to access the drive, and >> no hardware adapter to somehow connect it to a pc anyway. There are a >> few utils that made it a little more convenient to move files between >> the rampac and a tpdd, so to move files between rampac and pc you would >> use a 102/200 in the middle with the pc running a tpdd emulator. >> >> Still it has some little advantages. Small and simple. The driver >> software is smaller than most TPDD dos's, much smaller than TS-DOS but >> larger than Teeny. And it holds 512k. >> >> And the low level hardware interface is so simple and easy to operate >> directly even from basic, that you can actually use the raw space almost >> like ram if you are writing your own program. >> >> I have a 1 Meg version that actually has the entire hardware interface >> described right on the silkscreen on the back. because it's basically >> just 3 instructions with a tiny bit of explanation for the possible >> values for each. The normal RAMDSK software doesn't know how to access >> the extra space beyond banks 0 & 1, so the only way to use that is to >> write your own program that accesses banks 2 & 3 directly and uses it as >> raw space. >> >> TPDD is not convenient to access at the low level. It's only convenient >> at the user level using TS-DOS. Although TS-DOS does provide some hooks >> to provide high level file access functions in basic or from machine >> language. >> >> -- >> bkw >> >> >> >> >> >> >> >> > >> > Chris >> > >> > On Tue, Nov 19, 2024 at 7:44 PM Bert Put <[email protected] >> > <mailto:[email protected]>> wrote: >> > >> > Hi Chris, >> > >> > Not the screen so much, but your REX will already give you oodles of >> > RAM >> > in banks of 32K. So you can swap out and in, as many RAM banks as >> your >> > REX has space for. >> > >> > I just discovered that recently while playing with my (original) >> REX, >> > M-100 and T-102. >> > >> > Cheers, Bert >> > >> > >> > On 11/19/24 17:59, Chris Kmiec wrote: >> > > I have to admit, I have not been following the latest >> > developments for >> > > the 100/102. I have the backpack, REX# and REXCPM, but they have >> > been >> > > sitting lonely as for the past year or so my hobby time has been >> > taken >> > > over by the HP 71b. >> > > >> > > Anyway, I want to start playing with the 100-series again, but >> > have a >> > > question - are there any modern upgrades for the LCD screen and >> > increase >> > > in RAM beyond the 32Kb? >> > >> >> -- >> bkw >> >>
