Type N Complex
Refdisk and Diags
   Memory supported, cache, features 
BIOS releases
    Flash BIOS 05 from BIOS 03 or less
    BIOS Level Revison Features
Diagnostic LEDs
"N" / Upgrade 486DX2 66/33 MHz 61G2343
    Possible -xNx Overclock????
    -xNx Upgrades?
    Synchrostream on -xNx?

Refdisk and Diags

Reference Disk for Type 4-
Diagnostics for Type 4- (Common to all complexes)


Min/Max on system board: 8/64MB Parity, 8/256MB ECC
RAM: DRAM (PS/2 72-pin SIMM, ECC or Parity) 70ns
ROM: 128kb 
Cache: 8kb L1, 128kb L2 (DX2-66)
* 40 MB per second streaming data transfer.
* Error Checking and Correcting (ECC) memory controller
* 228KB L2 cache (write-through) on DX2-66 complexes
* 20 MHz DMA; 32 bit DMA can directly address all memory
* DMA supports Subsystem Control Block.
* Faster bus arbitration (than Base 1) for busmaster performance.
* Enhanced Dual Path Memory
* Subsystem Control Block enabled
* Vital Product Data support.
* Synchronous Channel Check support
* Data bus parity support
* A logging facility is provided (for ECC or system errors)..

BIOS Releases
BIOS revision 10 is for systems with the 859x system board that have been upgraded to a type 4 processor complex ( 486DX/2 33/66Mhz, Pentium 60Mhz, Pentium 66Mhz, or Pentium 90Mhz). Servers with the 959x system boards (e.g. 9595 and PC Server 500) with a type 4 processor should continue to use BIOS revision 8; BIOS revision 9 will provide NO enhancements for these systems. 

Flash Bios 10   Resolves an ABIOS time/date defect for OS/2 ONLY.
  10 Readme.txt
Flash BIOS 09 Seems to have an OS/2 bug. Not on PCBBS anymore...
Flash Bios 08
   08 Readme
   08 READOS2.ME
Flash BIOS 05
Flash BIOS 02

Got a 8595-OKD that came with a Type 4 (P60) complex. Every time I start it up, Win 95 comes up with the 1980 date. I can take the ref disk and use "Set Time and Date" and it will show the correct day and month, but the year will be 2799. Is that Y2K complient or what? You can change the date and exit back to the Main Menu, then go right back in Set Date and Time and it is back to the "2799" thing. It has revsion 08 bios. Any ideas?

The Revsion Level 10 cured the problem. It seems Win 95, at least SR2, has the same date problem as OS2 when upgrading a 8595 Type 1 or 2 complex to a Type 4 (P60/66).

Trying to flash BIOS 5 and up from 03 or Lower
  I ran into a problem with an N on a 9590. The BIOS was either 01 or 03, and it refused to configure with the new BIOS until I had used the old refdisk on Peter's IMMASTER. Booted and configured with the downlevel refdisk, flashedto 10, then reconfigured with the latest refisk.

Do you need the oldest refdisk? Ask ME

Complex BIOS Levels

Diagnostic LEDs (Extrapolated from the Type 3 information)
   The Type 4 processor board  has two LEDs; one in position CR1, and one in CR2. 

"N" / Upgrade 486DX2 66/33 MHz 61G2343

Artifact- Serial Link J5 on Type 4 complexes  (-xNx, -xPx, -xQx, -xYx)
     The serial link was (as far as I know) intended for the use with an earlier system management adapter, which didn't made it to the salesroom. The idea was to supply a sort of status-link to the processorboard and the SCSI- adapter(s) and the (possible) backplanes on the later servers. 
J3- Serial port connector to operator panel board.
J5- The "Flash ROM bank" switch -by the way- was originally planned for a sort of "emergency mode". Once you screwed up the Flash-BIOS you could toggle the bank, insert any working flash update in the FDD A: and restart the  machine, which takes the flash-image from the floppy drive and recovers (as it can be done on the 704 in the "Bios recovery mode"). However: the base boot-BIOS did not have the required routines to delete the loused up bank of the Flash-ROM ... and as far as I know the loading of an image from Floppy  does not work. Another useless feature. 
J6- Unknown Guessing at this- It wasn't marked on my board. 
CR1 and 2 - Diagnostic LEDs. Actual value open to debate. If the complex runs, who cares if they stay on or off?

40MHz OSC- MCA Bus Clock
33MHz OSC- CPU Bus Clock
50G8192  Not a clue. DMA Controller?
A82495DX Cache Controller

-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

9595 Main Page