S) 2.0 Motherboards
PS/2 last a long time, but sometimes due to mother nature, the user or just age the motherboards (planar boards in IBM-speak) fail. These can be obtained in many places both new and used. Beware that the price of a new motherboard is steep from IBM. Some third-party dealers have them much cheaper than in the past. DakTech (800-325-3238) carries some either new or as good as new form with a warranty. Check first, their stock varies. True Blue Parts 508-833-2225 (firstname.lastname@example.org) formally Micro Mart has the Model 80-Axx board for only $60.
Speak of the Devil.. Genesis Technology makes a motherboard replacement for the 55SX/LS which includes a new slot assembly and the motherboard. Unfortunately, it's ISA.
Reply Technologies sold new PS/2-type motherboards much cheaper than the IBM versions. These were high priced compared to normal PC-Clone motherboards, but if you have cash in memory and PS/2 proprietary items it is cheaper than replacing everything with new ISA/VLB/PCI based equipment. Also they offered Pentium processors, the ability to use standard SIMMs, and even VLB. These are still available used and new on www.ebay.com . The types of motherboards available from IBM are the 486DX2/66 and 486BL2/66, and almost every 486 type from Reply Technologies. The IBM motherboards are only available from the Boulder Surplus Parts division and are limited as they are no longer being made. Also they were made only for the 60, 65SX, 70 and 80.
There is a model 50/50Z and 55SX/LS planar board upgrade to 486SLC2/50 available currently from IBM. Note: these were discontinued in Sept 94 so they are limited, if IBM Direct doesn't have them call Boulder.
There are two versions of Reply's motherboards: the TurboBoard (for models 30, 50/50Z, 55SX, and 70) and the PowerBoard (for models 25/25-286, 30-286, 50/50Z, 55SX, 56 and 57, and 70). Using the model 70 as the example, the TurboBoard offers a 486SLC2 25/50 CPU, 387SX FPU socket, 16MB max using 3 70ns parity SIMMs, on board 1MB DRAM video, and 3 16 bit slots (one with video extension). The PowerBoard offers 486DX2/66, 486DX4/100, or 586/100 with Intel Overdrive socket, 64MB max using 3 70ns parity SIMMs, on-board 1MB (2MB upgrade) 64 bit local bus video, two 32 bit and one 16 bit (with video extension) slots. This is not a bad way to go.
There are no more Reply motherboards at Neointeractive. 04/24/00
No...unless you are VERY lucky(and probably the only one in the world).
Most times the screw holes will not even come close, then the slots will
be way off. Even if you got it fastened into your case you would
need a new power supply (which you would have to screw in some how) and
then new floppy drives etc. You are better off selling the system
and starting from scratch.
The model 70 and 80s with a 25MHz processor (8570/8580-Axx) come with
a 64k L2 cache which is very helpful. Benchmarks on a 20MHz model
80 and 25MHz model 80 with the cache showed Dhrystones at 4k for the 20MHz
and at 7.7k for the 25MHz which is a bigger difference than the 5MHz should
give by itself. As a matter of fact a Cyrix DRx2-40 processor in
a 20MHz machine gave only 8k Dhrystones, a cache of some sort should always
be obtained when purchasing a motherboard.
The following list shows what memory can be added. The difference of the Max System and Max Mother is what must be installed in the form of an expansion card.
Factory Max Max
Max mother is what can be physically added to the motherboard.
Max system is what can be added in the form of memory cards. Max
system is also the maximum memory of the mother and expansion card combined.
You can alter standard 72 pin Fast Page Mode SIMMs by adding the Presence Detect to them. This involves soldering a little blob across a few pins. Go to Peter Wendt's site for details.
Most of the times unless labeled it will be hard. IBM's numbering
system changes all the time and many times the cross-reference can not
be made. I got a SIMM here that has a nice label stating IBM
2M 85NS P/N 68X6127 FRU 92F0104. Now if that label
were removed I would only have 89X8922 IBM9314 L46056PE on the 18 chips
that are attached to the SIMM, now if someone can make 2M or 85NS out of
those three numbers I would be impressed as a call to
In OS/2 WARP there is a program that tells what is installed and the speed of the SIMMs. This program is the system information utility. Although it would be impractical for a large amount of unlabeled SIMMs, a few can be ID'ed this way.
According to Louis Ohland <email@example.com>:
The 9595 Type 4 (possibly type 3) can report in setup on the speed and
architecture (parity or ECC) of each chip by slot...
Unlike buying clone motherboards, the speed of the SIMMs you should need will usually be easily found out. For standard IBM, call IBM and for all other motherboard makers they should include it in their motherboard docs. Most of the time the 80ns memory is the most common on the newer machines. 120ns was used on the older PS/2s (i.e. 50's and 60's) and most 386s at or less than 25MHz can get by with 85ns. If you upgrade to one of the new 486 replacement 386 CPUs you will probably need 80ns memory unless stated that it will work with normal system memory, 70ns and faster is probably a good idea and should be used as 80ns and slower memory is becoming obsolete.
From Louis Ohland <firstname.lastname@example.org>:
The 90 / 95 / 85 prefer 70nS, but will tolerate 80nS. If you use a mixed pair of 70 and 80, the memory controller will use both at 80nS. You can hack a 60nS SIMM to work (adding Presence Detect), but the 60nS speed is not supported by the BIOS (nor is it a valid value of Presence Detect!), and the SIMM will be accessed no faster than 70nS.
IBM is pushing the MCA bus again. It is possible to make it as
fast as VLB, it comes close now. The new 700 machines will offer
a dual bus, MCA/PCI which will give the best of both worlds. The
*BEST* thing about MCA is it usually offers the PLUG-and-PLAY everyone
wants, at least in most cases. You simply copy the .ADF files onto
your reference disk then plug the new card in
A problem faced by ISA was device addresses, and ISA bus is only capable of 1024 device addresses while MCA can address 65,280. Also, MCA has far more grounds along the bus preventing radio emission. Lastly, MCA can share interrupts while ISA can not.
The speed of MCA is something underestimated by non-PS/2 users. It is a very fast and quiet (as far as RF interference goes). Some specs are:
The maximum transfer rates on a 10 MHz MCA bus:
16 bit MCA 32 bit MCA
Short Burst and Long
(not available) 80 MBytes/sec
Matched Memory Cycle
Since there have been so many discussions about all of this, I'm posting the OFFICIAL MCA specs. These are direct from IBM. MCA, as you will notice, has the capability to be faster than even the local bus technologies with a transfer rate of up to 160MB/sec. Hope all of this helps.
The basic transfer cycle on the Micro Channel is a minimum of 200ns (100ns for the address and 100ns for the data which results in five million basic transfer cycles per second for a device running in burst mode. As shown in Figure "Basic Data Transfer Mode", a data transfer operation is done in two steps. First the address for the transfer (either I/O adapter or memory location) is selected, then up to four bytes of data is moved across the data buffer.
Depending of the width of the data path (8, 16, or 32 bits) the instantaneous data transfer rate on the channel would be 5, 10, or 20MB per second. The matched-memory extension is a modification to the basic data transfer mode, which can improve the data transfer capabilities between the system master and channel-attached memory. When supported, it allows the basic transfer cycle of 200ns to be reduced.
The DMA controller on the system board requires two basic transfer cycles
to move either 8 bits or 16 bits of data. It moves the data from
the originator to a buffer in the DMA controller and then to the target
device or memory location. Because two cycles are used per 8 or 16
bits of data, the data transfer rate for DMA controllers is 2.5MB or 5MB
per second. For blocks of
When the Micro Channel is running in streaming data mode, the 32 address lines are only used during the first cycle of the transfer. These address lines are therefore available for transfer of an additional four bytes during each following cycle. This mode is called multiplexed streaming data mode and gives an effective width of 64 bits (8 bytes) for each cycle. The resulting effective data rate is 80MB per second. This is shown in Figure "Multiplexed Streaming Data Mode".
PS/2 Model 9595 (and possibly the 8595) can support the 100ns basic transfer cycle with the SCSI Fast/Wide adapterrather than the current 200ns. With the current cycle the Micro Channel is able to transfer sequential blocks of data with transfer rates of 20, 40, and 80MB per second.
Systems implementing the faster transfer cycle would be able to reach
transfer speeds of up to 160MB per second. These rates are essential
for advanced function bus masters, which must move large blocks of sequential
[From: email@example.com (Ralph Valentino)]
Here is a quick overview of the various bus architectures available for the PC and some of the strengths and weaknesses of each. Some terms are described in more detail at the bottom.
XT bus: Bus originally used in the IBM XT.
Comments: Obsolete, very similar to ISA bus, many XT cards will work in ISA slots.
ISA bus: Industry Standard Architecture bus (a.k.a. AT bus)
Comments: Ideal for low to mid bandwidth cards, though
lack of IRQs can
MCA bus: Micro Channel Architecture bus
Comments: Since MCA was proprietary, EISA was formed to
compete with it.
EISA bus: Enhanced Industry Standard Architecture bus
Comments: EISA is great for high bandwidth bus mastering
cards such as
VLB: VESA Local Bus
Comments: VLB is great for video cards, but its lack of
a good bus arbiter
PCI: Peripheral Component Interconnect
Comments: Combines the speed of VLB with the advanced arbitration
VL 2.0: Video Local Bus version 2.0
Auto configurable: Allows software to identify the board's requirements and resolve any potential resource conflicts (IRQ/DMA/address/BIOS/etc).
Bus master support: Capable of First Party DMA transfers.
Full bus master capability: Can support any First Party cycle from any device, including another CPU.
Good bus arbitration: Fair bus access during conflicts, no need to back off unless another device needs the bus. This prevents CPU starvation while allowing a single device to use 100% of the available bandwidth. Other buses let a card hold the bus until it decides to release it and attempts to prevent starvation by having an active card voluntarily release the bus periodically ("bus on time") and remain off the bus for a period of time ("bus off time") to give other devices, including the CPU, a chance even if they don't want it.
16Meg addressable: This limits first party DMA transfers to the lower 16 Meg of address space. There are various software methods to overcome this problem when more than 16 Megs of main memory are available. This has no effect on the ability of the processor to reach all of main memory.
Backward compatible with ISA: Allows you to place an ISA card in the slot of a more advanced bus. Note, however, that the ISA card does not get any benefit from being In an advanced slot, instead, the slot reverts To an ISA slot. Other slots are unaffected.
The MCA specs at 10MHz show sustained throughput very close to VLB and 20MHz MCA specs should be equal or superior to VLB, however, usually MCA cards do not operate at these faster speeds of 20MHz.
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No, they will not. MCA, unlike EISA and VLB, is not backward compatible with ISA.Some dual bus cards exist (DCA network card, ATI Ultra 8514/A) but these cards are specially designed to flip over and use the correct edge connector. There WAS an ISA to MCA module for the 286 based Gearbox. Chances are, most 286 Gearboxes were scrapped. So much for hope...
If it is possible on your machine it is Ctrl-Alt-Ins after Ctrl-Alt-Del. If nothing happens when you hit Ctrl-Alt-Ins at the prompt then you must use the reference disk to change CMOS values.
On the flash BIOS based systems, when the Surepath BIOS
splash screen pops up, press F1.
Bus mastering is the ability of the MCA card to directly read and write
to main memory. This allows the CPU do delegate I/O work out to the
cards, freeing it to do other things. If you want a bus mastering
card, you should specifically request it and expect to pay more.
Also not all cards are available in bus mastering form due to the fact
that they do not have to be independent to the rest of the system, and
some because they can't be independent.