Jump to content
Have You Played Atari Today?
2600|5200|7800|Lynx|Jaguar|Forums|Store  

Stuart

Members
 View Profile  See their activity

  • Content Count

    1,020

  • Joined

  • Last visited

  • Days Won

    1

Posts posted by Stuart

  3. Posted

    If it had a cache of the register contents, it could skip the load and write the value back to RAM when the memory bus isn't busy or you change the register file pointer.

     

     

    But that creates a problem that I think someone raised in speccery's thread: some programs manipulate register values by reading/writing direct to where the workspace is stored in RAM (it's a perfectly valid programming technique). So the contents of a cache would lose sync with the register values in the workspace in RAM. Unless you had some sort of system to detect when this happens.

    • Like 1

  4. Posted

     

    Called the Geneve 9640, it included a cartridge saver that would allow cartridges to be saved to disk, 640 K of 16 bit RAM, a 12 MHZ processor , 80 column display 512x424 graphics w/256 colour, an IBM XT keyboard, MDOS and "Advanced BASIC" and other niceties.

     

     

    [Pedantic mode on!]

     

    It's actually a 3 MHz processor, same speed (but more efficient) than the TMS9900. The 12 MHz crystal is internally divided to produce a 4-phase, 3 MHz clock.

     

    [Pedantic mode off!]

    • Like 2

  5. Posted

     

    So, I want to make sure I got this right. Set my MultiMeter to Ohms, turn on the peb, measure from both sides of the resistor. I get 0.025. So that would mean a 25k Ohm pull up resistor?

     

    No, you need to measure it out of circuit. Switch off the PEB, pull the resistor wires off those two pins you added, and measure across the resistor with it not connected to anything.

  7. Posted

     

    Hmmm... interesting! I think I might be able to figure it out. Do the darker lines on the drawing represent new wires installed?

     

    Yep, they grey lines are existing circuit, and the black lines the new stuff, with the connections being made either by piggybacking or by separate wires. There's one pin on one of the original ICs to cut as well and a wire soldered to it - look for the red 'X'.

  8. Posted

    The 16-bit 32K mod I have (http://www.stuartconner.me.uk/ti/ti.htm#32k_memory_expansion) is similar to that on the Mainbyte site but needs fewer chips, already incorporates the wait state defeat, and includes a switch (mount it on the back panel) to disable it so it doesn't affect any 32K on the sideport. The instructions aren't as comprehensive as the Mainbyte site though so you'll need to be experienced enough to be able to identify the ICs and connection points on the PCB.

    • Like 1

  11. Posted

     

    I mention I2C as the Arduina/raspberry crowd are being feted with hundreds of cheap add-ons that we are missing out on.

     

    I2C you can do through the joystick port - http://www.stuartconner.me.uk/ti/ti.htm#i2c_interface. The issue though is that pretty much every type of device will need a software driver to send/receive data specific to that device. Straightforward enough for the Arduino/Raspberry crowd where the population is in the millions, and the computers have got a gig or so of RAM.

  13. Posted

    BJGuillot, on 15 Apr 2017 - 4:46 PM, said:

    How does the speed of Cortex BASIC compare to TI BASIC? I believe Cortex runs from a ROM cartridge (so no GROM and GPL bottlenecks), but not sure if it runs just off VDP RAM or uses 32KB expanded memory. Also, not sure if it uses floating point for all variables or if it has integer specific variable support.

     

    I don't really know much about it and might have details wrong, but it could be a useful data point to understand what is really causing TI BASIC to be so slow.

     

    Cortex BASIC uses CPU RAM/ROM and needs 32K extended memory. Integer values in the range -32768 to +32767 are stored internally in an integer format, otherwise floating point format is used (you can't specifically define a variable as an integer).

     

    Cortex BASIC is **very roughly** 1.5 times the speed of XB. There's a little bit of benchmarking in this thread: http://atariage.com/forums/topic/245962-cortex-basic-in-80-column/?p=3376857. There's a bit about benchmarks using the 'top hat graph' here as well: http://atariage.com/forums/topic/215138-bitmap-mode/?p=3183359. All very non scientific as two BASICs can't run the exact same BASIC program ...

    • Like 1

  15. Posted

     

    Thanks Stuart, but why does the code start at >2A00?

     

    Shouldn't the ROM start at >6000, and the RAM with LBLA and LINES at >7000, with an additional GROM?

     

    An excellent point! I done the disassembly quite a few years ago so memory is a bit vague. The disassembler I used runs under XB, so what I think I done was a partial dump of the MiniMem RAM, swapped to the XB cartridge and reloaded that dump at >2A00. So the addresses in the listing have an offset of >4600 from the actual RAM addresses in the MiniMem. So for example address >2B8E in the listing + offset >4600 = actual address >718E in the MiniMem.

  16. Posted · Edited by Stuart

    Two files attached which may be of help/interest.

     

    "MiniMem LBLA Listing.doc" is a disassembly of the MiniMem with the LBLA loaded. Most of the code is the LBLA, but there is also some LINES and other stuff in there. It's a 'raw' listing - some data is interpreted as instructions, and this sometimes makes later instructions be misinterpreted, and so on. The first column in the listing is the memory address, the second column is the data at that address, and the third column is the disassembled instructions. The first and second columns are correct even where the disassembled instructions are out of sync.

     

    "MiniMem LBLA & Utilities Cartridge.a99" is a text file for my LBLA + TIBUG + Disassembler cartridge. It contains commented LBLA source, but has a number of changes from the original plus a bit of code shuffling so it can run from cartridge. All labels in the code in the form "Axxxx" relate to memory addresses in the first doc. The first bit of the LBLA, starting at >2B18, is workspaces and data. The main entry points are >2BA6 for "NEW" (label LBLANEW in my code) and >2BAC for "OLD" (label LBLAOLD in my code). There's then some shuffled code at A2BB0, but my code re-syncs with the listing at A2C3A.

     

    I've got various handwritten notes on how it works as well. Give me a shout if confused. ;-)

     

    MiniMem LBLA Listing.doc

    MiniMem LBLA & Utilities Cartridge.a99

    • Like 2

  18. Posted

    Shift838, on 25 Feb 2017 - 03:25 AM, said:

    I never had a problem either, but I was ordering a cable from IEC today and talking with a guy named Joe Miller and he said he used to work for TI and on the 99/4A project and said the whole reason they put the shielding around the 4A's was because without it it would get RF interference.

     

     

    I would have thought it was the other way round - the shielding is there so it passed the stringent FCC tests for emissions coming *from* the TI. If you can use it and you don't get interference on your radio or TV, I don't think you'll have any problems.

  20. Posted

    Shift838, on 24 Feb 2017 - 10:30 PM, said:

    I was told today that me taking the 99/4A mainboard out of the shielding may cause RF issues.from interference. Any experience from other tiers on this? Should I keep the shielding around the mainboard and mount it that way in my ATX tower case?

     

    There no top (component side) shield on the QI motherboard ...

  21. Posted

    Shift838, on 23 Feb 2017 - 1:19 PM, said:

     

    so are you saying a seperage 5v and ground line then to the cable? I think it's pin 19 for 5v and pin 2 for ground..

     

    Yep. If you go from handy +5V and 0V points on the motherboard to the pins on the connector on the end of your ribbon cable, which plugs into the cartridge. Might make no different at all but probably worth a go.

  22. Posted

    i have shortened the extension cable all the way down to 8 inches. XB 2.7 does work at 13 inches with no problem. But the Flashrom99 cartridge even with an 8 inch cable it seems to go to the menu and you get the wait circle at the bottom right, but it never gets past that.

     

    Might be worth trying to add some separate, thicker power and ground cables to supplement the connections you've already got through the ribbon cable. Should be easy enough to remove again if they make no difference.

  23. Posted

    Hmm. I reckon there's got to be a switch or sensor associated with that small board. In the first two photos above there are some silver pins coming out the opposite side to where the wires come in - can you see where they go to?

     

    With the photo of the removed motor, there are two bits of black plastic on the motor shaft. Are they both free to rotate on the shaft, or locked to the shaft? The piece nearest to the motor - is that completely round or does it have anything projecting from it? Is there anything set into the plastic, like a small magnet?

AtariAge
Forums
Store
General
Follow AtariAge

Copyright ©1998-2021 AtariAge

×
×
  • Create New...