Stuart

May 17

Aren't some parts of XB written in assembly?

May 17

4 hours ago, apersson850 said:

If you only look at the crystal, connected to the TIM 9904 clock generator for the TMS 9900, that was a 48 MHz one.

But of course changed to a 12 MHz crystal with the 9904A clock generator.

May 17

16 minutes ago, RXB said:

That would be a insane amount of Assembly and where would you put it?

Most 64K home computers of the period had BASIC written in assembly - usually around 16K - 24K. But they didn't have huge chunks of the memory map dedicated to the peripheral cards, cartridges and memory-mapped devices.

May 12

I got the impression that the two sockets on the video card itself were for user programs - so the sockets are empty when you bought the card. Support for the video card is built into University BASIC. As MAME emulates that, MAME must include the ROM dumps? See lines 440 onwards of https://github.com/MisterTea/MAMEHub/blob/master/Sources/Emulator/src/mess/drivers/tm990189.c.

May 1

"So do all the '|li' symbols refer to a virtual ground ..."

Those symbols are the common ground on the PCB. The common pin on each regulator is connected to it to give a common ground point, as is one side of the bridge rectifier.

April 30

38 minutes ago, OLD CS1 said:

Is it too late or too much of a wish to have the activity LED illuminate when the SID's *CS line is active rather than the TI address space? Real bugaboo of mine is that the LED stays lit most of the time even when not in use.

I think the SID's *CS is tied permanently low - the SID is continually processing the data in the data latch that feeds it.

April 25

(And further to Lee's explanation) the access time is significant for your (Vol's) previous argument that the 9995 is only faster if executing from internal memory. I couldn't find a copy of the Intel application note referenced but we could be fairly certain that the instructions are being executed from EPROM (otherwise why mention them?). We don't know though whether the data is processed in internal or external RAM on the 9995 - although it must of course be external RAM with the 9900.

April 24

Extract from the TI Microsystems Designers Handbook, showing that the TMS9995 gives around twice the performance of the TMS9900, with the 9995 clocked from a 12 MHz crystal, and the 9900 with a 4-phase 3 MHz clock derived from a 12 MHz crystal.

April 22

3 hours ago, mizapf said:

Just to be very clear about this. The left thing is a current M.2 SSD (1 TiB) which I just bought, the right one is a HD floppy disk (1.4 MiB).

Hence, the floppy disk fits almost 750'000 times into the M.2. The floppy disk is 3 mm high, 93 mm long, and 89 mm wide, which means 28.831 cm³. 750000 of them take up 20.7 m³, which means they could easily fill your bath room from floor to ceiling. (OK, I'll convert it: 731 cubic feet).

You still need to relate the measurements to Olympic-sized swimming pools and double-decker buses. ;-)

April 22

Vol, have you read post #20 of

April 21

I think you're getting confused with the clocks. With the TMS9900, you have a 12 MHz crystal feeding a TIM9904A which generates a 4-phase, 3 MHz clock for the processor. With the TMS9995, what they have done is incorporate the clock generator into the processor IC - internally the 9995 is still using the same 4-phase 3 MHz clock as the 9900. So you can't compare a [email protected] with a [email protected] - they're both internally using a 4-phase, 3 MHz clock from a 12 MHz timing source.

April 19

"This is a very unusual processor. The external data bus is 8-bit." Not very unusual I think. The TMS9980/81 had the same - 16 bit internally, 8-bit external data bus. Intel done the same on some processors.

"Instructions on the TMS9995 became much faster to execute, but only if they are located in the internal memory, or at least use data from the internal memory. But if an instruction and its operands are located in external memory, then it is executed, as a rule, even slightly slower. In addition, if we take an external clock frequency as the base, then even with the internal memory, the TMS9995 is slower than the TMS9900 at the same frequency." Only partially correct I think. The 9995 introduced instruction prefetch - it fetched the next instruction while processing the current instruction, and decoded the next instruction while storing the results of the current instruction. Much more efficient. Plus it didn't need the read-before-write cycle of the 9900. I'd be surprised if anything that the 9995 done was slower than the 9900, in internal memory or external.

April 15

The poor little processor is rather dwarfed by the other chips on the board. ;-(

I happened to notice a TMP9900 processor in this little lot: [https://www.ebay.co.uk/itm/402789789320]. It doesn't really have the look of a Chinese remarked chip, but then a date code of 1987 doesn't make much sense either.

April 10

45 minutes ago, xahmol said:

You could of course also let the user select PAL or NTSC.

Unfortunately those terms will be meaningless to many users ... ;-(

April 3

Have you checked for activity on the ROM and RAM chip select pins?

April 2

29 minutes ago, rkrenicki said:

I am trying to find a datasheet for the non-A version of the TIM9904, but I have not yet found one...

Look at page 249 onwards of http://ftp.whtech.com/datasheets and manuals/Datasheets - TI/9900-FamilySystemsDesign-1stEdition/9900-FamilySystemsDesign-08-Product Data Book.pdf.

April 2

I think the schematic is actually correct ... it specifies the clock IC as a 74LS362, also known as the TIM9904. This uses a 48 MHz crystal, and the values of L602 and C603 are calculated using an equation to relate to a frequency of 48 MHz. The values in the schematic of 0.33uH and 22pF satisfy that equation (the capacitance of the PCB also has to be taken into account). TI then switched to a TIM9904A, which uses a 12 MHz crystal. The values of L602 and C603 are calculated to relate to a frequency of 12 MHz. Values of 3.3uH and 50pF (or thereabouts) satisfy that equation.

So the L602 and C603 will be different values depending on whether you have an older motherboard with the TIM9904 or a later board with the TIM9904A. So you'll see different values in the original schematics and the QI schematics for example.

@rkrenicki - if you use the clock IC, crystal, L602 and C603 from your donor board, then they should be matched. You're using a 4-layer board though with a ground layer which will affect the board capacitance, and I don't know if that will be significant enough to affect things.

March 31

You're using a 48MHz crystal with the TIM9904? (As opposed to the 12MHz crystal (and associated timing components) for a TIM9904A?)

I see you're using quite a few 74HCT ICs. You might want to try 74LS. Although the HCTs are supposed to be compatible, I've found circuits where an HCT doesn't work but an LS does.

February 17

10 hours ago, Toucan said:

Out of curiosity, what is the difference between a TM and a TMS? What does TM/TMS stand for? I never see anyone asking about this, so it probably is common knowledge, but have been curious. Also, is a TMS better than a TM since there's an "S" added?

TMS is the prefix for their processors and support chips. TMS9900, TMS9995, TMS9901, TMS9902, ...

TIM is the prefix for related chips that are also available as part of the standard 74LS logic family. TIM9904 = 74LS362, TIM9905 = 74LS151, ...

TMP and TMX prefixes are also used for prototype and preproduction/validation(?) versions of the chips.

Some processors also available as "SBP" versions, which use a different type of logic (I²L). SBP9900, SBP9989.

TM990 is their range of microcomputer building block modules. http://www.stuartconner.me.uk/tm990/tm990.htm

TI990 is their range of minicomputers. https://en.wikipedia.org/wiki/TI-990

Have never seen what TM/TMS actually stand for!

February 2

1 hour ago, GDMike said:

The PEB transformer allows 110-240 vac in and makes sure 110 vac is out to the pcb power supply, so can't I just connect 110vac line in and bypass the transformer?

No! Not unless you want a big bang, puffs of smoke, and possibly an extended visit to your favourite deity. The PEB transformer output to the power supply PCB is at most around 20 Vac. You can use different connections on the transformer for 110 or 240 Vac input, but the output voltage is far lower.

January 30

Unfortunately the processor is still driving the address bus, and driving or reading the data bus, while waiting for GREADY.

January 29

1 hour ago, acme said:

Supplemental to my previous post:

I had an older BIOS version on my UDS10 (something 5.0.x) and "Autoincrement" wasn't available there. I had to perform a BIOS update.

Just clicked on a link in my test site. Instead of not being able to resolve the hostname, it gave me "Downloading webpage failed ..." So, resolving is sort of working, but not in the address-bar. And my guess is, the downloading failed because of my older v9.2 version - so normal behavior there - i think.

If you download the cartridge image now on my website and reprogram the cartridge, you should find it now resolves host names (let me know if not!). It calls a script on my website to do this using a hard-coded IP address, and that IP address changed a while ago ...

January 29

13 hours ago, acme said:

Yesterday I've got my first NanoPEB v1.1 (yay!) and set it up together with my the UDS10. Terminal Emulation II is working. So cable, UDS10 and TI seams to be operational. I could successfully log in into my linux-box.

Now I wanted to try Stuarts Internet Browser, but am totally lost. All ROM-links at his page are down.

The only version I've found for download, was one in this thread (v9.1), but it's not working. I guess I need the appropriate settings for my UDS10.

The only settings I can find are for >=v9.2, but these are settings for TIPI, as far as I understand, and are not working for me.

Can anybody tell me the UDS10-settings for v9.1? Or does any newer version of Stuart's browser exist for the NanoPEB? If so, could anybody point into the right direction?

Or did I miss something much bigger, and Stuart 's internet browser isn't developed any longer?

Any help is highly appreciated.

I'll put the v9.2 files back up this evening - seems they got deleted from the server somehow. But I need to tweak a hard-coded IP address in them first. I'll confirm when they're good-to-go.

Stuart

January 21

The +5V goes through a few ferrite inductors between the power supply and pin 1. You might well find it works fine by connecting pin 1 direct to the power supply, but you might run into problems if you were to, for example, try to get the console through the FCC emission regulations again. ;-)

January 21

My NanoPEB runs quite happily from a short +5V power cable I've run direct from the TI internal PSU board and out through the case by the expansion socket. So I still need to plug the NanoPEB in, but I don't need an external mains adaptor.

My NanoPEB consumes about 80mA at +5V, and the console itself about 950mA.

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