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IBM ps2 P70 portable repair thread

Sorry for trying to warn everyone that at least one of those caps is known to be poorly manufactured and very close to a bunch of tiny tracks that will destroy your board. I mean why bother taking anyone's advice ever? Why not learn that the motorway isn't suitable for yoga practice without trying it first?

It probably takes 20 minutes to pull the card, replace the cap. But hey, one less working P70 in the world raises the value of mine, so go right ahead!

Oh and I left the other caps as they are because they were a different make and not leaking.
 
I just find blanket recapping a shotgun approach. Especially on 1980s through hole electrolytics.
 
VERAULT said:
The Texelec OPL3 Resound 2 board came in so I popped it in and coppied the file from the website to the reference disk.

View attachment 1276293
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Uh, the image shows "Parallel Port" as "PARALLEL_1" 03BC-03BF (old... IBM parallel 1]
You need to set it to "PARALLEL_2" 0378-037B (clone LPT1)

Parallel Port Address Assignments is one place.

"Note: 03BCh was used by the parallel port on the (old) Monochrome Display Adapter (MDA). I suspect that in certain video modes, placing Extended Mode registers on 03BCh would interfere with video memory."
 
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Torch said:
I wonder if MCA ports can simply be daisy chained like the I/O port of my Model III or the ISA adapters on my 1000EX?
If so, I can simply buy a female MCA connector and parallel it off the back of the riser by soldering on a short section of ribbon cable, then mount the sound card wherever.
I'm leaning more towards no as BIOS recognizes ports with nothing plugged into them.
Click to expand...
EDIT: I re-read your post. It isn't totally hopeless, as I think you want to simply relocate a slot and are not adding one [say, four slots, not three]. The stock planar ADF should support the relocated slot.

You most likely cannot use both slots at once because the MCA uses A01 to setup each card. The setup line is unique to each slot.

I'm not sure if the extra length of conductors will affect the circuit properties enough to keep the relocated card from meeting the timing window.

The empty slot is for a DBA-ESDI device that is supposed to go there. It is possumble to use the DBA-ESDI slot for other things, but you only have IRQ14, which might not be so bad with a PIO card.

Foundt it. Direct Bus Attachment Pinout has the details

16 Address lines
16 Data lines
DMA support [ARB/GNT]
Streaming capable
PREEMPT
BURST
 
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ardent-blue said:
Uh, the image shows "Parallel Port" as "PARALLEL_1" 03BC-03BF (clone LPT1)
You need to set it to "PARALLEL_2" 0378-037B

Parallel Port Address Assignments is one place.

"Note: 03BCh was used by the parallel port on the (old) Monochrome Display Adapter (MDA). I suspect that in certain video modes, placing Extended Mode registers on 03BCh would interfere with video memory."
Click to expand...
its bewn working fine the way it is on every program i threw at it. I will only change it if I need to use my Sdlpt or something changes.
 
VERAULT said:
its been working fine the way it is on every program i threw at it. I will only change it if I need to use my Sdlpt or something changes.
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As long as programs use the BIOS defined Parallel address, seems to be happy. OR it could actually support 03BCh. We're all in this together...
 
ardent-blue said:
Uh, the image shows "Parallel Port" as "PARALLEL_1" 03BC-03BF (old... IBM parallel 1]
You need to set it to "PARALLEL_2" 0378-037B (clone LPT1)

Parallel Port Address Assignments is one place.

"Note: 03BCh was used by the parallel port on the (old) Monochrome Display Adapter (MDA). I suspect that in certain video modes, placing Extended Mode registers on 03BCh would interfere with video memory."
Click to expand...
ardent-blue said:
As long as programs use the BIOS defined Parallel address, seems to be happy. OR it could actually support 03BCh. We're all in this together...
Click to expand...
Not sure I understand the potential conflict, what would be at 0x3BC-0x3BF other than a parallel port, if the MDA's parallel port was there as well?

As far as video (are these correct?):
  • CGA: 3D0-3DF (decodes)
  • EGA: 3C0-3DF (decodes)
  • VGA: 3B4, 3B5, 3BA (and more in 0x3C0-0x3DA)
Here's is my config, seems to work fine.
55SX_config.jpg
 
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VERAULT said:
Its now back together and the first thing I noticed when trying to run things is how SLOOOOOOOOW it is. I dont know what this cyrix 486 is doing but it barely feels like a 486. It must be an extremely slow or early 386 bus on this board.

View attachment 1275153
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I don't see in the thread if you ever figured this part out, but the reason your Cyrix 486DRx2 is so slow is because you don't have the Cyrix utility installed to enable clock doubling and the internal 1 Kb L1 cache.

You have a 40 MHz oscillator installed, which runs the CPU at 20 MHz, with clock doubling, it will run at 40 MHz. The 387 will stay at 20 MHz, unless you also get a clock doubling 387.

There's some info over at Vogons on how to get these features working, and the requisite utilities. https://www.vogons.org/viewtopic.php?f=46&t=45756

It's unfortunate that IBM didn't include cache on the motherboard, that leaves a lot of potential performance behind. If you need more performance, you can try and find the TI version of the same chip, which has 8 KB of cache. IBM also made a clock doubled 386/486 hybrid of their own design, as well as a clock tripled version with 16 KB of L1 cache. These are harder to find and can be expensive. I have a clock doubled 66 MHz version, and with the 16 KB of L1 cache and 128 KB of L2 cache, it performs about as well as a 486SX 40. I don't have a FPU on mine.
 
GiGaBiTe said:
I don't see in the thread if you ever figured this part out, but the reason your Cyrix 486DRx2 is so slow is because you don't have the Cyrix utility installed to enable clock doubling and the internal 1 Kb L1 cache.

You have a 40 MHz oscillator installed, which runs the CPU at 20 MHz, with clock doubling, it will run at 40 MHz. The 387 will stay at 20 MHz, unless you also get a clock doubling 387.

There's some info over at Vogons on how to get these features working, and the requisite utilities. https://www.vogons.org/viewtopic.php?f=46&t=45756

It's unfortunate that IBM didn't include cache on the motherboard, that leaves a lot of potential performance behind. If you need more performance, you can try and find the TI version of the same chip, which has 8 KB of cache. IBM also made a clock doubled 386/486 hybrid of their own design, as well as a clock tripled version with 16 KB of L1 cache. These are harder to find and can be expensive. I have a clock doubled 66 MHz version, and with the 16 KB of L1 cache and 128 KB of L2 cache, it performs about as well as a 486SX 40. I don't have a FPU on mine.
Click to expand...
Wow, thats an eye opener. I had no idea there was software necessary for this cpu!

So that vogons link is a bit vague as far as my exact cpu, it seems to list them in general and I find no explicit instructions for pdf for my exact cpu and which utilities it requires. The closest match for the utilities it mentions is CyrixDLC_SXL so I suppose I can try that out.
 
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Ok. So I got the Cyrix.exe program and copied it to the P70. For a baseline these are the default settings on the cpu if you do a query (cyrix.exe -q) and these are the benchmarks with checkit for the stock settings:
IMG_20240820_134616.jpg
IMG_20240820_132900.jpg

Here are all the switches for the Cyrix.exe program off the vogons site
The options are:

Option Action
------ ------
-a[-] Enable [disable] A20M input.
-b[-] Enable [disable] BARB input.
-c[d] Two way assoc. [direct-mapped] cache. -cd for SXL 2x mode
-d Raw dump of control registers and exit.
-e[-] Enable [disable] 1k cache via CR0.
-f[-] Enable [disable] FLUSH input.
-h Print this help screen and exit.
-i<n> Inhibit non-cachable region <n>, where n={1,2,3,4}.
-k[-] Enable [disable] KEN input.
-m[-] Enable [disable] cache of 1st 64k of each Mb.
-o Override check for existence of Cyrix DLC chip.
-p Disable all power saving modes.
-q Query DLC configuration status and exit.
-r[-] Disable [enable] cache of 640k -> 1M ROM shadow area.
-s[-] Enable [disable] SUSP i/o.
-v Print version number and exit.
-x<hex>,<size> Don't cache <size>kb from segment <hex>.



So I ran Cyrix.exe -cd -f -i1 which resulted in the following screen changes and benchmarks:

IMG_20240820_134711.jpg
IMG_20240820_134826.jpg


So what do you guys thing? Obvious improvement. Any ideas on more switches I can try which would be practical in the P70?


Thanks @GiGaBiTe for the heads up of the Cyrix utility. I had no idea it was software controlled.
 
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Every system is different, so you really have to experiment to get the maximum performance out of yours. Or if you're just happy with just about double the performance, you can leave it where it is. You could also try swapping out the 40 MHz oscillator with say a 50 MHz oscillator for a slight overclock and see if the system is stable.

It looks like you have both FLUSH and BARB disabled, I think you need at least one to do cache invalidation, else the cache gets stale and causes the system to crash or become unstable.
 
GiGaBiTe said:
Every system is different, so you really have to experiment to get the maximum performance out of yours. Or if you're just happy with just about double the performance, you can leave it where it is. You could also try swapping out the 40 MHz oscillator with say a 50 MHz oscillator for a slight overclock and see if the system is stable.

It looks like you have both FLUSH and BARB disabled, I think you need at least one to do cache invalidation, else the cache gets stale and causes the system to crash or become unstable.
Click to expand...
Flush is enabled.

Guess im just curious about the cache settings. What the p70 can work with
 
Hello i'm completly new to these type of PC's. I'm a system engineer of 22 years old and managed to get one IBM ps/2 P70 model. I have an IBM ps/2 p70 and when I plug it in and turn it on, you can hear it start up. The green light of power is on and the 3 lights of numlock capslock and one more blink and then go out. The power light stays on and you can hear the PC running. However, the screen remains completely black and no output is given or program is loaded on the screen. Now you should know that there is a hard disk in this PC that may be empty or formatted (this is not certain) and that there is no reference diskette inserted in the PC at startup. Do these problems indicate the absence of the reference floppy disk and would the device give an output on the screen as soon as I insert a reference floppy disk at startup? Please know that I will make this reference floppy disk myself using a floppy disk and with the correct file of IBMfiles.com. Or do you think the screen is broken or something hardware?
 

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