Hi Guys,
I'm currently working on a clone of this card as a hobby project. My goal is to make a card with a boot capability on an PC XT clone computers.
The card I have as a reference is exactly the same as
SomeGuy's.
First, I tested it with x286 PC - it works with 5.55 BIOS only. SCSI HDD detected and bootable.
With 6.3U - no go. SCSI HDD was not detected. Tried with different SCSI devices(two types of HDD, blueSCSI, SCSI2SD) - no difference.
With XT PC 6.3U-086 - SCSI devices not detected. With 5.55/5.53 - drops some garbage on screen when detecting devices. Which is expected as the BIOS is designed for higher CPUs.
Does anybody have an idea what could be wrong with my card? I wonder why 6.xU BIOS doesn't detect any SCSI device.
This is my PC XT mainboard:
8088-TXM-8-10
Krille, could you please if possible share the 5.55 BIOS source code. It would save me a lot of time digging in the current one. Or compile it for 8086 CPU, I would expect it will work on my XT machine.
The project's location for reference:
SCSI-ISA-5380
Regards
Oleg
Hi Oleg,
By coincidence, I have also made a SCSI adapter design based on the 53C80, mine contains a Zilog clone of this chip, the Z53C8003.
Simply because this chip is available to me at the moment, and it's a very basic chip which in my feeling seems to suit an XT PC.
I didn't have any card available for study/reference so I based my design on the Zilog SCSI chip datasheet.
I chose port 320 as the base port, and made jumpers for IRQ5/7, and DMA3.
I also added the /SCSI_EOP signal with a jumper to optionally connect it to the SCSI controller chip if I found it's supported.
This design is integrated on my Rev 2 XT mainboard and I have also made the design on a 8-bit adapter card with Realtek LAN, COM1 and boot ROM socket fixed at C800 as well. I am waiting for the 8-bit adapter PCBs which are delayed by DHL, so I can only test on the mainboard PCB for the moment.
So far I have done testing and debugging and my mainboard is working correctly. So I have now moved on to do some testing of the SCSI controller with various drivers and while searching I came across this thread.
My mainboard contains a V20 and I have tested the 5.55 bios, 6.3U-186.BIN as well. I simply included the 4k of these BIOS codes after enlarging them from 4k to 8k with empty space, then copied the BIOS with my other XT BIOS code and put the ROM in the F0000 space in the next available space block. My BIOS is like this:
8k blank - 8k blank - 8k blank - 8k blank - SCSI BIOS (8k) - HDFloppy22 - XT-IDE BIOS - PC-XT BIOS by Phatcode
What I found in my tests is that indeed the SCSI bios is loading, and it seems to attempt to write in the space which is after it's initial 4k, which is probably expected to be occupied by the 2k scratchpad RAM. Which of course corrupted my EEPROM.
So I proceeded to test with a normal EPROM which prevents corruption, just to be able to test and see what this BIOS will do.
I didn't expect things to work of course, but I am getting the option ROM message, and it reports to be "SEARCHING ..."
I can see the HDD activity light come on briefly once which seems to indicate that some communication to the HDD happened.
But the BIOS doesn't get past the "SEARCHING ..." message.
I have tested with IRQ5 and with and without DMA channel 3 connected to the chip
Actually, I am not looking for an option to boot from a SCSI drive, I just want SCSI available for file transfers and backups of my XT PC, and I use XT-IDE integrated for booting the XT itself. Since I am using a combined BIOS in the F0000 segment space, trying to boot using a SCSI BIOS will probably mess up the cooperation of the other BIOS images anyway on my configuration, which is what I found with other 8-bit SCSI cards so I used those without a BIOS with a driver only.
In my testing efforts on the 53C80 clone chip, I can report that the Mediavision PAS16 integrated SCSI driver which I found in the SCSI! bundle has the most response so far.
The options I used are:
DEVICE=C:\TSCSI\ASPIMED.SYS /P0320,05 /RW
Which selects port 320, IRQ5 and resets the SCSI chip, then sets a short wait period of a few seconds.
When I don't attach a drive, this aspi driver loads into memory successfully, reports the card to be present and I can use SCSITEST.EXE which finds the ASPI driver and adapter correctly.
When I attach a harddisk however, the driver doesn't complete loading, it stops at the polling phase of the driver load.
When I try to power up a harddisk, and use SCSITEST.EXE to poll the harddisk, it's not completing the detection properly either.
A SCSI CDROM seems to time out on detection/polling and then "no devices connected" is reported.
I believe I connected the SCSI bus correctly which seems pretty straightforward and I did apply termination on the adapter and at the drive, termination diode and fuse etc as usual.
I also tried with and without the parity bit option enabled on the drive but got the same results of not completing the device polling phase.
For reference, you can see some info on my project here:
I need to update this page soon since the prototype mainboard is currenly fully working and replaced revision 1 in the ATX case now.
Except for the SCSI of course.
I know I am taking a chance and skipped a few steps in my process, but I expected to need to revise the prototype PCB anyway and simply wanted to see if any current drivers would support this SCSI chip directly.
My goal is to have full integration and only needing to add a video card and a soundcard to complete the XT system.
As you can see on my web page, I did manage to get a simple 53C400 card(memory mapped connection) working fine already, and I have tested a Future Domain TMC-950 based card as well, though those drivers are not optimal on an XT and take rather long to load.
I just want to include SCSI because it's ideal for swapping an external harddisk for backup and file transfer purposes on an XT system.
I wanted to share my findings since I saw your post was recent and I am doing something relatively similar
I haven't completed all my testing yet, so I am still searching for more existing drivers and testing everything I can find.
I could opt to make a 4k ROM/2k RAM design as well to more closely match the card in this thread, but I am not there yet to have chosen to go this path, and still hoping to get the current design to work. I just want something very basic that is sufficient to use a SCSI harddisk externally and perhaps an internal SCSI CDROM as well. I am not too focused on high performance since the 8-bit bus speed is limited anyway.
I may also go the route to switch to a 53C400 chip design which I know to be working already in my system.
But from the historical viewpoint I like the 53C80 more because it's more original since it was the first chip type developed by NCR and feels more straightforward to me than the 53C400. I just want to gain an "essential" SCSI function with as little as possible components. I had some free space on the mainboard which suited this kind of design exactly.
I still hope I can get this very basic chip to function, and would appreciate any tips or ideas.
Of course if I get it to work, I will share the findings here as well
Kind regards,
Rodney