If you're going to write your own (or heavily modify the) operating system, i wonder if getting the filesystem out of RAM and onto a different device would make more sense than expanding RAM without more address space.
-Alex On Wed, Nov 20, 2024, 22:43 Mike Stein <[email protected]> wrote: > 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 >>> >>>
