32K expansion question

[AtariNostalgia]

When you add the 32K expansion, do you have a total of 32K available or 16+32, adding on top of the included memory?

Does that mean when calling the top RAM, is it changed?

[HOME AUTOMATION]

The 16k, I believe you are referring to, is connected to the video display processor's bus ...not the 9900's.

 

But all is available!

[AtariNostalgia]

So the total RAM would be 48K right?

[HOME AUTOMATION]

I'm not so good at the maths, but that sounds about right.

 

But they work differently, are for different purposes ...accessing the 16k, is somewhat slow and cumbersome.

 

...not one contiguous space.

 

... not recognized as 48k by most software.

 

XB can use both, ...conditionally.

Edited March 2, 2021 by HOME AUTOMATION

[+mizapf]

27 minutes ago, AtariNostalgia said:

So the total RAM would be 48K right?

This is one of the cases where you would expect a simple answer, but this is harder to give than it seems. The problem is that your question about "total RAM" implies that you can put two pieces together as one.

 

As said above, the 16 KiB of the console are video RAM and cannot be directly accessed by the CPU. Nevertheless, it serves as data memory or as memory for interpreted languages like BASIC.

 

The 32 KiB memory expansion is, however, addressable by the CPU, and can hold any kind of data or programs.

 

Hence, you have two different RAMTOPs.

[apersson850]

1 hour ago, mizapf said:

Hence, you have two different RAMTOPs.

It's even more complicated than that, since the 32 K RAM expansion shows up in two different areas in the TI 99/4A design. The CPU memory space is split in eight 8 K pages.

 

0: Monitor ROM and GPL interpreter.

1: 8 K RAM when the memory expansion is attached.

2: Space for device drivers.

3: Space for ROM in software modules plugged into the console.

4: Built in 256 bytes RAM and ports for access to VDP (and its 16 K RAM), sound, speech, GROM and such stuff.

5,6 and 7: 24 K RAM when the memory expansion is attached.

 

With the expansion attached there are three different RAM pools, for different purposes.

 

[AtariNostalgia]

Thanks. That is some seriously complicated stuff...

[Retrospect]

I remember seeing an advertisement for the TI99 some time ago, an it stated that with all the memory add-ons you had something like 48K (or was it 72K) of RAM.  They never said you couldn't use it all as one area of memory but to my understanding you can't have like one 72K game or whatever.

[Count9929A]

38 minutes ago, Retrospect said:

I remember seeing an advertisement for the TI99 some time ago, an it stated that with all the memory add-ons you had something like 48K (or was it 72K) of RAM.  They never said you couldn't use it all as one area of memory but to my understanding you can't have like one 72K game or whatever.

could it be 52K? It's the result of the console 16K + 32K expansion + 4K minimemory

[+Ksarul]

The most RAM you could have that would be CPU accessible without masking out the console ROMs would be 32K (expansion RAM) + 8K (Cartridge space) + 8K (DSR space) = 48K. Note that TI also made a card that did this, and that card also bank switched memory in most areas to get up to 128K. The card was never commercially produced, however. SAMS ended up being a much better solution for larger memory spaces, as there are a lot of the 1M boards in circulation now along with an ever-expanding software library that uses it.

[Retrospect]

This is grainy and low quality but this advert, states RAM upgradable to 52Kbytes.

 

I dunno there's just something I consider misleading about that statement.  I'm sure there was an advert that counted the Rom size into the total memory, been looking for that one but can't seem to find it again

[+adamantyr]

The 52k was I think if you had a mini memory cartridge installed. That was during TIs support phase the only cartridge that offered RAM in the cart space address.

 

Honestly, it just feels like if it weren't for expense (RAM chips didn't drop in price until 82-83), the 32k expansion should have been part of the base console. 

[RXB]

I think there is a confusion when people read this ad.

Extended Basic has 40K of GROM and 3 banks of ROM 4K for a total of 52K this is combined GROM/ROM in this statement.

Gramkracker and Gramulator ad was 72K was 40K GRAM cartridge space and GROMs 0, 1 and 2 of 8K for total of 72K GPL GRAM/GROM

and also 16K ROM so the ad would say 88K total.

[+arcadeshopper]

http://www.mainbyte.com/ti99/hardware/ti_specs_2.html

 

has a nice picture and description.. basically if you add 4k from minimemory, 32k expansion and 16kvdp ram=52k

 

Later we had the 8k superspace module making it 56k..  

[AtariNostalgia]

So now one knows precisely how much RAM is available to BASIC once the 32K expansion is placed on?

[+Ksarul]

27 minutes ago, RXB said:

I think there is a confusion when people read this ad.

Extended Basic has 40K of GROM and 3 banks of ROM 4K for a total of 52K this is combined GROM/ROM in this statement.

Gramkracker and Gramulator ad was 72K was 40K GRAM cartridge space and GROMs 0, 1 and 2 of 8K for total of 72K GPL GRAM/GROM

and also 16K ROM so the ad would say 88K total.

Rich, there is one caveat to your statement here: 5 GROMs in the XB cartridge only provide 30K of addressable space (6K per GROM), not 40K (8K per GROM). Yes, later solutions were able to use the full 8K per GROM space (GRAMulator and GRAM Kracker), but that capability only became available long after this advertisement was made.

 

Based on what was available from TI at the time, the largest cartridge could only have 42K (30K GROM and 12K ROM), although the ad ignores the bank-switched portion of the cartridge memory space. The box counts all of the available memory spaces with one exception: Speech Memory, which is also in a memory space of its own, like VDP and GROM memory are. Some TI ads reflected this additional space, others didn't.

[jstimson]

29 minutes ago, AtariNostalgia said:

So now one knows precisely how much RAM is available to BASIC once the 32K expansion is placed on?

Regular console BASIC could not access the extra memory.  So with that all you have is the 16k that is really the memory native to the video chip.

 

Extended BASIC gives you access to the 32k.  Under that setup you have about 24K of space for actual program code, and almost 14k of space for things like variables.  That 14k is within the memory native to the video chip.  So out of the 32k, you get 24k for program code.

 

Edited March 2, 2021 by jstimson

[+mizapf]

56 minutes ago, AtariNostalgia said:

So now one knows precisely how much RAM is available to BASIC once the 32K expansion is placed on?

It is in fact an issue with the console (video) RAM for the installed TI BASIC, as there is no command for checking the available RAM. Extended BASIC adds the SIZE command (which is not available in programs, only on the command line).

[GDMike]

But thankfully I've got 1meg of SAM's..mmmmmm. isn't it just nice

[Ed in SoDak]

In console BASIC, I entered...

 

10 DIM A(1811)

20 GOTO 20

 

...and it ran sucessfully. Adding 1 to the DIM statement to make it 1812, it stopped with "Memory full in 10". Adding more program lines would require reducing DIM A further. Somewhere is listed the bytes used for each command. Knowing this, with a little math you could determine your program's size and free memory left. The SIZE command of EXB is so much handier!

 

 

[AtariNostalgia]

I love my TIs, but this is convoluted. So If the first 16K is shared with the video ram, the longer the BASIC program it is, the less video RAM is available, which in theory, would make colors and sprites to start disappearing.

The above example isn't a true representation of the maximum allowed lines in BASIC. You are using an array, which uses much less memory than an actual line of BASIC could. You are counting how many 'A's can be created dynamically until memory is full.

Anyhow, this has left me with a splitting headache, and finds me wondering how such a system exists without it being made more of a deal about back in the day.

[HOME AUTOMATION]

actually, I think  TI BASIC programs are limited to just over 12k! the other VDP TABLES are reserved(mostly).

 

IIRC ...each array element's default length is 10 chars. 

 

Ah, an un-dimensioned array's default is a set of 10 elements.

Edited March 3, 2021 by HOME AUTOMATION

[AtariNostalgia]

TI Extended BASIC is so underrated outside the TI community that it angers me. I think it's one of the best and most complete BASIC's out there.

[HOME AUTOMATION]

I used TI BASIC until about 1996, and managed to accomplish most of the same tasks I now do in ASSEMBLY ...albeit much slower.

[GDMike]

I'm thinking multiplication and division are easier to accomplish in basic than assembly. I need to brush up on those two items in my assembly knowledge.