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Here are the 5 most recent blog posts…

Replacement IDE BIOS [PC-98]

PC-98 A-Mate series (Ae, Ap, An) all have a limited BIOS which supports IDE drives up to 540MB, some later machines support up to 4.3GB. SCSI controllers and disks can go bigger, up to 30GB-ish in some cases.

However, support for anything bigger is just not possible on the stock system, such as my PC-9821AN. Fortunately someone has developed a custom ROM overlay that replaces the standard BIOS routines that interface with the IDE drive to support up to 120GB (the limit of LBA28 or CHS addressing).

It is technically possible to write this ROM to an unused card on the PC-98 C-Bus and have it initialised at boot time. The most common method would be something like a SCSI card, where the SCSI functions are not needed.


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2019/06/30 19:30 · john

Using 1.44MB Floppies as 1.2MB Floppies [PC-98]

The PC-98 uses a weird 1.2MB 3.5“ disk format, that is almost, but not-quite compatible with traditional IBM PC 3.5” 1.44MB floppies (it can use the disks themselves, but cannot read the contents).

On Linux, to prepare a standard 3.5“ high density floppy as a PC-98 1.2MB floppy you need to install the tool ufiformat:

First install it from your standard package repo (it's in the Ubuntu/Mint repositories):

$ apt-get install ufiformat

Then insert a blank floppy in your internal/external/USB floppy drive and reformat it (where sdm is the device name of your floppy drive of course):

$ ufiformat /dev/sdm -f 1232

If you look at the output of dmesg now, you'll see that it has turned the format of the floppy itself into a 1.2MB disk:

[3034644.733661] sd 15:0:0:0: [sdm] 2880 512-byte logical blocks: (1.47 MB/1.41 MiB)
[3034714.697763] usb 1-1.5: reset full-speed USB device number 51 using ehci-pci
[3034715.039175] sd 15:0:0:0: Power-on or device reset occurred
[3034715.679181] sd 15:0:0:0: [sdm] Spinning up disk...
[3034716.841769] .
[3034718.249766] .
[3034718.495158] ready
[3034719.007182] sd 15:0:0:0: [sdm] 1232 1024-byte logical blocks: (1.26 MB/1.20 MiB)
[3034719.775155] sdm: detected capacity change from 0 to 1261568

You can now happily dd a PC-98 floppy image to the disk:

sudo dd if=MS-DOS\ 6.20\ \(System\ disk\ #1\).hdm of=/dev/sdm bs=64k status=progress
19+1 records in
19+1 records out
1261568 bytes (1.3 MB, 1.2 MiB) copied, 41.8561 s, 30.1 kB/s
2019/06/30 13:03 · john

Hydra Scart Switcher (and OSSC tests)

I have lots of systems to connect via RGB scart, at least 15 at the last count. I wanted a single display format (HDMI), so I have everything going through an OSSC Scaler; I needed a multi-way scart switch in front of it in order to handle all of the systems I wanted to connect up.

I chose to go with the Wide Hydra from Lotharek, which at first glance looks to be an excellent solution.

However, I've since found that it is extremely sensitive to both the type of scart cable you use, as well as the type of signal being sent over the cable; specifically the voltage of the video sync line (scart pin 20).

The device is designed closely to the scart specification which lists a voltage of 0-1v for most of the lines… however lots of systems don't appear to be anywhere near this specification unless you make some modifications to the video signal they're outputting.

As a result, virtually none of my systems work as-is with the Hydra, when they used to work perfectly directly to a Sony PVM monitor, or work perfectly when connected directly to an OSSC scaler.

I'm going to try and summarise my findings here, I'll also include the findings of other kit connected through the OSSC, but not dependent on the Hydra - VGA and Component inputs, for example:

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2019/06/14 09:24 · john

Home Office Move

On moving to our new house in 2014 I made the third of our four bedrooms into a small office space for my computing and video game collection. It worked quite well (though became increasing cluttered) over the years, but by 2019 I was forced to downsize and move to the fourth bedroom to make space for a another bedroom for the second of our mini-people.

As such, a lot of effort was put in to designing the new, smaller space to accomodate the bulk of the computing/gaming equipment, with the advantage of new technology (including HDMI adapters for almost everything, to do away with the CRT monitor) and a need to box up almost all games for those systems where they could be pre-loaded to HDD or flash cards… as a result it's a much busier room, but actually works much better.

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2019/06/10 09:34 · john

Personal Projects

2019/06/10 09:32 · john
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  • Last modified: 2019/06/10 09:31
  • by john