Jump to content


  • Content Count

  • Joined

  • Last visited

Community Reputation

961 Excellent

1 Follower

About apersson850

  • Rank

Recent Profile Visitors

7,528 profile views
  1. Such features usually require that the design includes the necessary feedback routes. Which adds cost, and that's nothing you want in a home product like the TI 99/4A. Memory is easy enough to test, as you can both write to it and read from it. But a computer like the 99/4A usually can't test the sound, because it can only generate it. It has no way to "listen" to what comes out, so it can't determine if the sequence used to generate the sound really was successful. The same is true for the image on the screen. In production, it's common to include a number of test points on the PCB. Then a testing device is probing these test points, while the computer runs some specific software. Then the computer may emit sound, and the test device will probe sound output line to see if the desired tone is actually emitted.
  2. I have a floppy disk with the game. I got it pre-release, since I knew people who worked for TI in Sweden back then.
  3. We happened to stop in Pepin, just randomly. There was some historical landmark, a sign claimed. Turned out to be due to Laura Ingalls Wilder. We decided to go see the replica of her first home, then ended up in Stockholm.
  4. The attraction is the roller coaster. Nog riding it, but seeing it. It's the only place I've been where a mall has such a thing. Apart from that, I found nothing to buy.
  5. That's the advantage. When running programs where both the code and the workspace is in expansion RAM, the speed increase with 16-bit access is roughly 110%. I found that signifcant enough to do the job with installing the 16-bit memory. And then some, since I actually added 64 K RAM to the existing 32 K RAM upgrade, not just replaced the standard memory expansion.
  6. Well, I'm heading home on Friday (10th). But the remaining days of this week I have work to do. Due to the holiday, I had Saturday - Monday off. I was in Minneapolis two days ago (Thursday). I have a colleague here too, and he had never visited Mall of America. Kind of a must when you are here.
  7. OK. Spent the day looking at the surroundings of Missisippi river. Found a place called Stockholm in Wisconsin. Almost like home.
  8. But with a single chip like that, you don't get 16 bit wide access, right? You get the memory but not the speed upgrade, as far as I understand.
  9. Anybody here who lives near Rochester, Minnesota? I happen to be there right now...
  10. I got the basic idea to my design from somebody who installed 64 K RAM, but only used half of it. The reason for installing 64 K was simply that the memory chips were 8 bit wide. So that design used 16 K from each 32 K chip, to get a 16 bit wide memory data bus. Seeing that, I thought I could improve on the design by adding the logic which would allow the use of all of the memory in the chips.
  11. The one I have adds 64 K RAM in the console. It's all at 16 bit wide bus. Thus you can have your workspace anywhere. It's as fast as console RAM pad anyway. The 32 K covering the area for the normal memory expansion is on by default. If switched off, any external memory expansion (in the PEB) will be visible instead. So by switching off the internal memory, you go back to 8-bit speed, but also has a second page of 32 K RAM. The remaining 32 K RAM in the console can be switched on in 8 K banks. Thus you can overlay all other areas in the console with RAM. This includes console ROM, DSR space etc. Of course, you can't return to a normally operating machine with memory and all VDP ports and stuff at >8000 - >9FFF replaced with RAM. You'll crash immediately. But inside your own program, your can turn on that bank and use it as some buffer memory, or whatever, as long as you disable it before returning to the console. Another options is to transfer a part of your program to that area. Then, when your assembly program is called, you can enable that area, run your program there, jump back to your program elsewhere and disable the memory before you return. This means you can have space for up to 32 K of software, in your own assembly program, which is all loaded and can be accessed by just a toggling of some CRU bits. You can also copy all console ROM to RAM, then switch in the RAM. Now you can modify all interrupt vectors and such stuff. You can for example use the timer in the TMS 9901 to create an interrupt to a scheduler, if you want to run a multitasking assembly program with pre-emptive task switching. Another possibility is to have a contiguous 64 K RAM area in the machine, if you temporarily need to manage a lot of data. These different banks are all switched in and out by CRU bits at >0400, so all this can be done under software control. This is my own design. I never made any PCB, though, so it's all soldered in piggy-back on existing circuits in the console. I've also never used a Commodore 64 in any depth, but I do know it had a similar capability. It could be 64 K RAM, but not at the same time as having access to all system services.
  12. If you by Pascal refers to the UCSD p-system, then that's a totally different animal. It doesn't use the native file system at all. It just does disk access by sectors, then implement the p-system's traditional file handling on top of that. It sets its own rules completely. This is why storage devices that don't have the concept of disk sectors don't work with the p-system. A RAMdisk can work, but the access to the disk is not the same as the standard system either. The p-system has its own implementation of DSRLNK, so you have to be careful not to make assumptions about how the standard DSRLNK behaves, or your device driver will not work correctly with the p-system.
  13. Don't remember. Can check when I'm back home.
  14. No, it isn't. Since it's my own clock design, nobody else had any use for it. I do have some wiring diagrams and software myself, though. If I remember correctly now, I had the problem that a couple of disks got ruined, so some of my source code is missing, I think. I only have the executables left.
  15. I still have one. But I've never had any of the rainbow colored ink ribbons required to use the color function.
  • Create New...