Thinkpads Forum

Hi folks.

In order to clear things out and perhaps be able to install 768 MB RAM in the ThinkPads 770X and 770Z, I need some help to determine the memory matrice in these machines.
The is a slight chance, that a bit in a byte in the CMOS map perhaps could alter this limitation.

There's three slots, DIMM-0, DIMM-1 and DIMM-2 available.
DIMM-0 is reachable if the machine is disassembled.
DIMM-1 and -2 is the user upgradable slots.

DIMM-0 has two banks, 0 and 3
DIMM-1, has bank 1 and 4
DIMM-2, has bank 2 and 5.

Each bank can take 128 MB.
A 128 MB stick is a one-bank mamorystick.
A 256 MB 16-chip is a two-bank memorystick.

In DIMM-0 sits a 64 MB stick from the factory.
It uses one half of either bank 0 or 3.
It can be replaced with at least a 128 MB stick.

It's well known, that these machines can take 2 sticks of 256 MB RAM, giving a total of 512 MB usable RAM, but what truly happens ?

Using 256 MB in either DIMM-1 or DIMM-2 swaps out all the memory in DIMM-0.
I have 512 MB in mine, but using SiSoft's Sandra, it told me, that DIMM-0 was free, even though that there still were a 64 MB stick in it.

Which of the DIMM-1/-2 is it, that swaps out the access to DIMM-0 ?

What works, what doesn't ?

DIMM-0, DIMM-1, DIMM-2

64 MB 64 MB 64 MB = OK
64 MB 64 MB 128 MB = OK
64 MB 128 MB 128 MB = OK
64 MB 128 MB 256 MB = ?/OK
64 MB 256 MB 128 MB = ?/OK

128 MB 128 MB 256 MB = ?/OK
128 MB 256 MB 128 MB = ?/OK

256 MB 128 MB 128 MB = ?
256 MB 256 MB 128 MB = ?
256 MB 128 MB 256 MB = ?
256 MB 256 MB 256 MB = Not OK.

256 MB 0 MB 0 MB = ?
256 MB 128 MB 0 MB = ?

0 MB 256 MB 256 MB = OK.

It's important to clear out what the machine does, in order to narrow down the possibility of the one bit in CMOS, that points to the specific bank/banks and probably just needs another value.

In reverse it seems to be the case, that the CMOS in the very similar machine, 600E, has a bit in a byte, that can be changed, so the soldered onboard base-memory (66 MHz) in 600E can be ignored, in order to avoid trouble, when upgrading the 600E to 100 MHz FSB/P-III.

I hope I make myself understandable

Which combination of RAM worked for you in the 770X/Z ?
Which didn't ?
What happens when using a 256 MB stick in the basememory alone ?

Kindest regards
Brian

Brian,

I've put 256MB PC100 sticks in the 0 memory slot of the 770Z in an attempt to break the 512MB memory limit, but it didn't work. I've only been able to get a stable machine with 128MB sticks in slot 0 and slot 1 and a 256MB stick in slot 2 for 512MB total.

128MB in slot 0 and 256MB sticks in slot 1 and slot 2 still results in 512MB RAM, as does leaving the standard 64MB in slot 0 and adding 256MB sticks to slots 1 and 2, or removing the memory completely from slot 0 and adding 256MB sticks to slots 1 and 2.

In the past I have been told that slots 0 and 1 are shared and this is the reason that the slot 0 memory is mapped out when 256MB sticks are installed in slots 1 and 2.

Regards,

James

Thank you James.

My own working max-combination were until now:

DIMM-0 : 64 MB [Ignored]
DIMM-1 : 256 MB
DIMM-2 : 256 MB

Exchanging the P-II366 with the P-III850 gave me the opportunity to take out the 64 MB, so now it's:

DIMM-0 : 0 MB
DIMM-1 : 256 MB
DIMM-2 : 256 MB

It took me three hours to follow the HMM for the first time in 1½ year, so in the first place, it'll be fine if the used combinations among ThinkPad-users can be recalled from the hidden depths of the past.

Otherwise I'm forced to have my machine taken apart for research.
Perhaps I'll just do that.
I have the appropriate sticks laying around, 64/128 and 256 MB.

With these, a handful or two of reboots and SiSoft Sandra, the true use of banks/DIMMs can be recovered.
That'll have to wait until next week or at least until tonight

Thanks again James.

Kindest regards as usual
Brian

Okay....

I've been told by Sharedoc, that byte 2B in CMOS Base 128 controls the SDRAM banks..

I quote:
"in 600E byte 2B of CMOS controls the SDRAM banks. Bit b0 disables internal 32M memory. By changing the content from 80 -> 81 the 32M is disabled.

Bits b1 ... b7 control other memory banks.

Here is my trial log (I don't remember how much memory I had installed, propably 32 + 128 + 128)

Initial value 80
81 (disables internal 32M)
82 and 83 ?130M
84 228!
88
90 294
A0 228M!
C0
7F no post"

Now, two jobs

One: I would like everyone who read this, to tell what she or he see in CMOS, byte 2B.

Hold F1 down at cold boot, until EZ-setup appears.
Go into "Config" - hit CTRL-D

Look at the position marked with this **.
0 1 2 3 4 5 6 7 8 9 0 A B C D E F
00
10
20...............................**
30
40
50
60
70


What does it say ? 80 ?
In order to get out, hit ESC, EXIT and Restart.

Report also how much RAM you have installed, and in which DIMMs/slots they sit.
Ex. DIMM-0: 64 MB, DIMM-1: 128 MB, DIMM-2: 128 MB

This applies to the 600, 600E, 770X, 770Z
Report also which machine you have.

Job two:
I will try to avoid burning my hands, when I take my machine apart tonight and fiddle with different combinations of RAM and different settings in CMOS.
There just *have* to be a way
Anyone knows this feeling ?

I hope someone will report back.
Every piece of information is welcomed with a blessing and kind thoughts.

Thank you

Brian

Okay.
Here's the result.

ThinkPad 770, P-233MMX, TX-chipset.
Onboard-DIMM-0: 32 MB, Bank-0
DIMM-1: 128 MB, Bank 1-3
DIMM-2: 128 MB, Bank 0-2

Installed RAM: 294.912 KB
Maximum usable RAM: 228.800 KB

The 64 MB in DIMM-2/Bank-0 were ignored.
Bank-0 in DIMM-0 had highest priority.

Bit b0=1 disables Bank-0, but don't liberate Bank-0 in DIMM-2.
Result: 196.032 KB

Bit b1, b2, b3 =1 disables something on Bank 1,2,3 and leads to error.
Result: 163.264 KB

Bit b0+b1 or b2 or b3 disables 2 Banks in a row.
Result: app. 130.000 KB

Bit b4+b5+b6+b7 = 0 or 1 have no effect.

Byte 2B, initial value: 80, RAM 228.800 KB

81: 196.032 KB. Onboard RAM ignored.

82: 163.264 KB, Sandra couldn't launch. Error.

83: 130.000 KB.

84: 163.264 KB, Sandra couldn't launch. Error.

85: 130.000 KB.

88: 163.264 KB, Sandra couldn't launch. Error.

89: 130.000 KB.

90: 228.800 KB.

A0: 228.800 KB.

C0: 228.800 KB.

Odd combinations:

91: 196.032 KB. Onboard RAM ignored.

A1: 196.032 KB. Onboard RAM ignored.

C1: 196.032 KB. Onboard RAM ignored.

F1: 196.032 KB. Onboard RAM ignored.

F0: 228.800 KB

8F: ERROR. No boot.
I guess all banks are ignored, and not even BIOS can copy itself in order to boot.

8E: Didn't try, but I guess it'll show about 32.000 KB, since only Bank-0 is open.

Hmm...too bad. No luck in Byte 2B

I did try with my daugthers ThinkPad 600 with P-II 300 MHz, 440BX-chipset.
Same thing goes. No luck.
Same results.

Now......I'm dead tired and I'm off for tonight

Tomorrow is another day

[Crossposted in Wim's BIOS forum]
_________________________________
Post Scriptum:

Please notice, that SiSoft Sandra reports 4 banks in an old Thinkpad 770.

DIMM-0, bank 0
DIMM-1, bank 1-3
DIMM-2, bank 0-2

In an 770, the bank are shared.

But....in the 770Z....*all* DIMMs have seperate/individual banks.
DIMM-0, bank 0-3
DIMM-1, bank 1-4
DIMM-2, bank 2-5

Now...something just *gotta* determine, swapping out the DIMM-0 in the Thinkpad 770X/Z.....grrrrr.

Goodnight. See 'ya all later.
_________________________________

Kindest regards
Brian