N Type 4 Complex
Rf90954a.exe Reference disk for Type 4 Complexes
Rd9095a.exe Common Diagnostics for all 859x / 959x Systems

"N" / Upgrade 486DX2 66/33 MHz 61G2343
   ECA0002 01291500 Errors
Memory supported, cache, features 
Support for Convenience Partition on >3.94GB Drives
BIOS releases
    Flash BIOS 05 from BIOS 03 or less
    BIOS Level Revison Features
Diagnostic LEDs
    Possible -xNx Overclock????
    -xNx Upgrades?
    Synchrostream on -xNx?

"N" / Upgrade 486DX2 66/33 MHz 61G2343
CR1,2 Diagnostic LEDs
J3 Serial Diagnostics Link to operator panel
J5 Artifact
J6 Unknown
JMP5 FLASH ROM Bank Switch
U3 BIOS Odd 61G2347
U10 BIOS Even 61G2350
U19,20,26,38,42 KU82490DX cache
U29 A82495DX Cache Controller
U31 40.0000 MHz OSC- MCA Bus Clock
U33 33.3300 MHz OSC- CPU Bus Clock
U47 50G8192  Not a clue. DMA Controller?
U85 LT1085CT VRM
Supports 041xh and 043xh CPUIDs HERE  David Beem put some thought into steppings.

   If you get Intermittent 01291500 errors and intermittent hangs, or SYS000915 errors under OS/2 using an N complex, FRU 61G2343, then this ECA probably applies. NOTE: the upgrade Type 1 DX2-66 FRU 92F0145 is NOT affected.
   To check if your complex is affected, note the manufacturing P/N on a sticker just below the CPU. If the manufacturing number is 82G3513, 06H3368, or 61G4072 with no patch wire on the back [described below], it is affected. NOTE: I have a 61G4072 with a patch wire on the front. It seems to work. But the U69 and U60 ICs do not match.
Complexi 06H7263, 06H7264, and 06H7265 with the wire patch are not affected.
Complexi with FRU 06H7266 are not affected. [ed. New level production?]

Wire Patch on Back
  There are two ICs, U60 and U69. U60 is 74F04D, 14 pin and U69 is 74ABT374D, 20 pin. The patch wire runs from the top left of U69 across to the right, then down to R1, then from the bottom of R1 to the left, where it connects to the bottom right of U60. If your 61G2343 does not match the U69 (74ABT374D) and U60 (74F04D), then this ECA does not apply.

-xNx Overclock?
From  Tatsuo Sunagawa
   The board accepts  40.00M oscillator instead of 33.33M without any changes of BIOS.  But with 45.00M, it doesn't  work. I don't have same type oscillator, so I 'm using  square metal  package oscillator with socket.
   (Ed. Does this mean an AMD/Cyrix 486DX-80 might work? The 486DX-80 was for systems with a 40MHz clock.... Watch the voltage! The DX-80 was a 3.45v chip, FAIK...)

-xNx Upgrades?
From Tim Clarke
Type-4 DX2-66 will take:
Intel/IBM DX2-66 (5v parts, x2 clocking)
Intel DX2-66ODPR (5v parts, x2 clocking)
All others *fail* to reach 'logo' screen (presumed BIOS 'sensitivity')

But with this possible overclocking,
Hi Louis,
    Yes, the 'sensitivity' I remarked upon was in relation to x3 clocking ratios and above, *not* increasing the 'base clock' and staying with x2 clocking.  My initial reaction is that a 40Mhz x2 (i.e. 80Mhz) chip would work very well, especially those with the 'bigger' 16KB L1 on-chip cache.

Ed. Please report experiences... Also, do be careful- the parts may be able to take the overclock... Make sure the side fan works. Keep the complex clean.

Current N Upgrade Attempts
   I tried a Socket 3 transplant onto an N (proceedure performed by Jim Shorney). At the same time, a 40MHz oscillator was tried. The 40MHz oscillator wasn't cooperation. At present, the Socket 3 modified complex will not respond on a 9590. Possibly too crude of a planar??
   Complex refuses to run on a model 90, but came up on an M class 95 planar. Still refused to complete booting with anything other than a DX2-66. Interposer failed to enable booting with a POD. Possible timing or cache related problems.

Is there a Synchrostream controller on an N?
> Praytell where is the Synchrostream controller on the N? I   thought that it was the metal cased chip 50G8192, but it's used on  the N and the P. And the P has the yellow or blue SSC....

From Peter-
   I'm afraid it hasn't got one. The SSC is a feature of the last releases for MCA IBM made before they dropped it. The Lacunas have it - and the Pentium T4 have it. I think the -N- hasn't got it. It "only" has the normal 40 / 80MB/s MCA interface. (32/64 bit burst mode).

9595 Server 95 (AKA "Server 95 466") (Type 4 ref. disk)
1NG - 486DX2-66, 16/256MB (ECC), 540MB SCSI-2, 2.88, 101 KB
1NT - 486DX2-66, 16/256MB (ECC), 1GB SCSI-2, 2.88, 101 KB
1NV - 486DX2-66, 16/256MB (ECC), 2GB SCSI-2, 2.88, 101 KB
9595 Server 95 Array (called 95A) (9 drive bays - Type 4 ref. disk)
3NG - 486DX2-66, 16/256MB (ECC), 3 x 540MB SCSI-2, 2.88, 101 KB
3NT - 486DX2-66, 16/256MB (ECC), 3 x 1GB SCSI-2, 2.88, 101 KB

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