CF-M32 IRQ Fix and Right BIOS Settings
by Dr. Xin Feng, 4/8/01
Many CF-M32 users asked: "why the USB port is disabled in BIOS by default, while it actually works?" I think I've finally got the answer. This answer also leads to the solution of IRQ (interupt) conflicts between PCMCIA cards.
As you all know, there are totally 15 IRQs in a PC. Here is a list of IRQs and their usages in CF-M32 after you loaded the non-PnP default settings in BIOS and enabled USB.
As you see, there is only one IRQ, IRQ9, left for PCMCIA cards. As a result, you can only use one PCMCIA card even there are two slots there. To be more accurate, you can use two cardbus cards, or one cardbus and one non-cardbus, because cardbus cards can share the IRQs with PCMCIA controllers. If your PCMCIA card is non-cardbus type (most PC cards are) and refuses to use IRQ9, then you are out of luck.
Fortunately, Windows 2000 comes with a nice feature. By default, it filters out IRQ7 and makes it available for add-on cards. Therefore, you do can use non-cardbus cards while the USB port is enabled if the card welcomes IRQ7 and 9. I'm not sure if Win98 has this feature too.
Unfortunately, all my PCMCIA cards (SCSI, MODEM, Ethernet, Wireless, CompactFlash...) refuse to take IRQ9, 10 and 11 -- IRQ5 and 7 only. Therefore, I have never been able to use two cards simultaneously. I finally got too tire of card swapping and forced myself to look into the problem. Fortunately, after playing around with different BIOS settings, now I can use any two of my cards at the same time. Here's how.
Press F1 to get into BIOS and load non-PnP default (never load PnP default as it never worked). Make the settings like this (Note: Latterly I have been using bidirectional mode intead of EPP).
The key point here is to free IRQ5 and 7 for PCMCIA cards and force USB to use IRQ10. I found that IRQ10 could be used only by USB port and nobody else could use that IRQ. Let sound port use IRQ11 to free IRQ5. Also make sure that the parallel port uses IRQ7 (Windows 2000 will later free up this IRQ). If you boot your CF-M32 with one (only one) PCMCIA card inserted, assign manually IRQ7 to it, see picture below.
Why? If a PC card automatically chooses IRQ5, then the USB port thinks IRQ10 not available (there must be a design flaw here) and will take IRQ7 instead if IRQ7 is free. If IRQ7 is not free, then USB port will still take IRQ10, unhappily though. If you boot your CF-M32 with two cards inserted, then you don't need to manually assign IRQ7 to one of them, because the two cards will mostly take up both IRQ5 and 7 automatically. Although Win2000 later reports a problem with IRQ10, everything will be just fine as most USB devices actually never use IRQ.
1) CF-M32 does not have a PnP (Plug-and-Play) friendly BIOS and it allows PC cards use IRQ5 and 7 ONLY. Let the sound port use IRQ11 instead of 5. Never load the PnP default settings or choose any PnP options.
2) There is a bug between IRQ5 and 10. If IRQ5 is used, IRQ10 is then unusable and the USB port intends to use IRQ7 instead of 10. Therefore, if you always boot your CF-M32 with only one PC card inserted, manually assign IRQ7 to it. This way USB will always use IRQ10 no matter it is available or not.
3) Only the USB port can use IRQ10 and you'd better force it to do so. If USB uses a IRQ other than 10, you cannot use two non-cardbus cards simultaneously due to the shortage of available IRQs.
This is why the USB port is disabled by default and Panasonic has never claimed a USB port in CF-M32. This was why CF-M32 was discontinued soon after its release -- it's BIOS had a serious design flaw in its IRQ-assign algorithm. So sad, Panasonic may have had a much better result with CF-M32, if it had honestly told consumers what I have just told you in this article. Other than that, it is still the best laptop man ever made.
[04/12/01] Even I force the PCMCIA card to use IRQ7, the card still cannot function well if it is the only one present at booting. Therefore, the safest booting is to have either two cards inserted without manual IRQ assigning or no cards at all. Booting with one card inserted seems troublesome. And, some network cards do not work well while inserted into the lower slot.
Click here for my original tip for this great mini laptop.
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Xin Feng Company