Re: Tempest memory

BIT = 1 Bit
NYBBLE = 4 Bits
BYTE = 8 Bits
WORD = 16 Bits
DOUBLE WORD = 32 Bits
 On Oct 10, 2011 11:59 PM, "Mark Shostak" <shostakmark@gmail.com> wrote:

> One small correction.
>
> > On the 6502 a word is 16 bits or two 8 bit bytes
>
> On the 6502, a word is 8 bits.
>
>
>
> On Mon, Oct 10, 2011 at 8:34 PM, vectorlist-steve <
> vectorlist@arcadehacking.com> wrote:
>
>> **
>> 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> 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 Tue Oct 11 03:23:14 2011