Re: Tempest memory

Comments inline Kevin...

On 10/10/2011 5:44 AM, Kevin Moore wrote:
> Ugh... Thanks. After seeing the memory map laid out, ie
> 0x2000 - 0x23FF --> M3 (D0-3) and M4 (D4-7)
> It make sense now.. Vram 0 M3 and M4.

M4 is the suspect since you were having issues with D7. If you have a
spare 2114 ram on hand, hold it on top of M4 with all of the pins making
contact and see if the new ram resolves your issue. This test is not
100% guaranteed but if the error is resolved then you KNOW which chip
needs to be replaced.

>
> So by doubling the ram like they do, you can now write an 8 bit word
> correct?
>
> So for example, an 8 bit word will get split between M3, and M4

Yes, two 4 bit nibbles is one 8 bit byte

On the 6502 a word is 16 bits or two 8 bit bytes

>
> I'm thinking I should have paid more attention in microprocessor class
> in college some 20 years ago.
>
> Thanks for the help.
>
> Kevin
>
>
>
>
> On Mon, Oct 10, 2011 at 12:00 AM, vectorlist-steve
> <vectorlist@arcadehacking.com <mailto:vectorlist@arcadehacking.com>>
> wrote:
>
> Check out page 5 of the Tempest Drawing Package (DP-190 2nd Printing)
>
> Decoding is grouped in the Vector-Generator Address Selector box.
>
>
> VRAM
> ---------------
> 0x2000 - 0x23FF --> M3 (D0-3) and M4 (D4-7)
> 0x2400 - 0x27FF --> L3 (D0-3) and L4 (D4-7)
> 0x2800 - 0x2BFF --> K3 (D0-3) and K4 (D4-7)
> 0x2C00 - 0x2FFF --> J3 (D0-3) and J4 (D4-7)
>
> VROM
> ---------------
> 0x3000 - 0x37FF --> N/P3 (D0-7)
> 0x3800 - 0x3FFF --> R3 (D0-7)
>
>
>
>
> On 10/9/2011 9:34 PM, Kevin Moore wrote:
>
>
> Ok, so I don't often come across a memory problem that the
> tempest self test doesn't point me to.
>
> But today my fluke is showing me a decode error at 2c00 bit 7
> . Which is affecting vectors in game.
>
> I'm trying to figure out which RAM chip is giving me problems
> short of pulling all the chips.
>
> Are there any documents out the explaining how memory is
> allocated and used on Atari boards?
>
> I would really like to learn how to find the correct chip or I
> assume narrow down to two chips
>
> Kevin
>

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Received on Mon Oct 10 21:34:26 2011