The required values were taken from here (CRC-24/OS-9). It allows you to define custom CRC settings. Now the freeware hex editor HxD comes in handy. Value of any “patched” or modified module, or OS-9 cannot load the module from disk or find it in ROM.” (see The CRC Value on page 1-8 of the OS-9 2.4 Technical Manual.) However, there seems to be a catch: “OS-9 does not recognize a module with an incorrect CRC value.
After all, if the CDI220/60 with the same nvdrv device driver has both 32 KB NVRAM and a working RTC, why wouldn’t the CDI470/20, right?
Let’s see if we can patch the nvr device descriptor. Patching the ROMsĪdditionally, I prepared some patched ROM files:
Luckily, the service manual gave me a hint for which EPROM to use: 27C400. Last, I needed a couple of CD-i player ROMs, but I really didn’t want to open up all my CD-i players and swap the chips during the tests. For the 32 KB, I used a combination of M5M5256DP and DS1216C, as described here. For the 8 KB NVRAM, I chose DS1643 over the original M48T08 TimeKeeper. Then, I attached a DPDT (double pole, double throw) toggle switch to the points shown below to keep the setup as flexible as possible. Having a good theoretical basis, I chose a player (CDI470/20 – Mono IV) that had nothing left to loose and repaired it. There are at least two more 774 Byte nvdrv modules and some more nvr modules with different content, but none of these are relevant for the experiment at the moment. Interesting: both 8 KB and 32 KB device descriptors use the same device driver.
The modules with the same checksum are marked in the table above. The nvdrv modules are either 774 or 878 Bytes in size. The last three bytes contain the CRC-24 checksum, E9B44E in this case. Following to offset $50, there is the name of the driver: nvdrv. For example, at offset $3A is M$PDEV, the offset of the device driver name: $0050.
With the information in Device Descriptor Modules on page 1-8 of the OS-9 2.4 Technical I/O Manual, we can dissect the module even further. $1FF8 = 8 KB (8192-8, reserving 8 Bytes for the RTC registers). If you have recently installed or moved your computer, verify that the CD-ROM cables are connected correctly.PD_RSIZ field in the nvr device descriptorĮven though there are many different nvr modules, all of them use one of these values:ġ.
If you are using Windows 98 or Windows 95, verify the computer is running in 32-bit mode by clicking Start, Settings, Control Panel, double-click System, and click the Performance tab. Additional information on bootable disks is on our boot disk page. However, if the CD-ROM does not work, refer to the next and final possibility. If the CD-ROM does work from MS-DOS, this indicates there is a Windows corruption issue.
If you attempted the recommendations above, try booting from a Windows 98 diskette or another bootable diskette with CD-ROM drivers to see if the CD-ROM works from MS-DOS. If the computer can boot from the disc, you are encountering a Windows driver related issue. If you attempted the recommendations above, boot from the Windows disc to see if the computer can detect and boot from the disc. Try booting a CD or bootable diskette Windows 2000, XP, Vista, 7, and later users It's also possible that the drive is bad and needs to be replaced. If the CD-ROM drive is not in the Device Manager, the drive's cables may not be connected properly. Reboot the computer to reinstall the CD-ROM drive. If listed with a yellow exclamation mark or red X, remove the CD-ROM by highlighting the drive and pressing the delete key. Within Device Manager, verify the CD-ROM has no exclamation marks or red X's. In Windows Vista and later, click the Device Manager link on the left side of the System window. In Windows XP and earlier, click the Hardware tab and then the Device Manager button.If, after cleaning the drive and CDs, you still get errors, it's likely the disc drive is bad. For instructions on cleaning your CDs and disc drive, see the computer cleaning page. If all but one or two discs fail, the disc drive is bad or dirty. Make sure you have tested more than one CD in the disc drive, as it may be one CD that is bad or dirty. If a CD-ROM or DVD-ROM disc drive in your computer is not reading discs correctly, the following tips and information may help you fix the problem.