Issue with SD card on SC131

Marc Kip

unread,

Dec 18, 2025, 2:19:01 PM12/18/25

to retro-comp

Hello all,

I'm a newbie on the SC131 but managed to get it to boot. It will perfectly load the build-in CP/M with option "C". Everything seems to run fine. Rom version is RomWBW HBIOS v3.5.1, 2025-05-21

The issue starts with the SD card. I have read the User Guide, especially the sections 3,4 and 5. I tried to partition the SD card with FDISK80:

B>fdisk80

FDISK80 for RomWBW, UNA, Mini-M68k, KISS-68030, SBC-188 ----

Version 1.1-23 created 3-June-2023

(Running under RomWBW HBIOS)

HBIOS unit number [0..2]: 2

Capacity of disk 2: ( 14G) 30367744 Geom cf601010

Nr ---Type- A -- Start End LBA start LBA count Size

1 FAT32 lba 0c 260:0:1 1023:15:16 66560 30301184 14G

2 00 *** empty ***

3 00 *** empty ***

4 00 *** empty ***

Reserved 4 x 8Mb CP/M slices

>>I

>>R

Reserve how many CP/M slices (256 max.) [8]: 4

4 CP/M slices have been reserved

>>N

New partition number: 1

Starting Cylinder (default 260):

Ending Cylinder (or Size= "+nnn"): +500M

>>t

Change type of partition number: 1

New type (in hex), "L" lists types: 0b

>>p

Nr ---Type- A -- Start End LBA start LBA count Size

1 FAT32 0b 260:0:1 1023:15:16 66560 30301184 14G

2 00 *** empty ***

3 00 *** empty ***

4 00 *** empty ***

Reserved 4 x 8Mb CP/M slices

>>W

Do you really want to write to disk? [N/y]: Y

Okay

FDISK exit.

After a reboot subsequently initializing CP/M drives C:, D:, E: and F: with CLRDIR C: -Y etc.

Unfortunately the issue begins with:

B>pip c:=b:stat.com[v]

VERIFY ERROR: =B:STAT.COM[V]

It looks like that slice/drive C: is pointing to somewhere undefined. Drives D: etc. procedure the same error. Omitting the verification results in an unusable file although the size information is correct.

Changing the SD card with an alternative one brings up the same problem.

As the documentation is quite clear and I didn't found any similar posts in this forum I'm obviously doing something wrong. But what?

Any help appreciated!

Thanks,

Marc

Doug Jackson

unread,

Dec 18, 2025, 2:39:17 PM12/18/25

to Marc Kip, retro-comp

You may need to do a CLRDIR C: to get the directory ready for files.

--
You received this message because you are subscribed to the Google Groups "retro-comp" group.
To unsubscribe from this group and stop receiving emails from it, send an email to retro-comp+...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/retro-comp/4661d203-71fa-454a-b44f-9f8732048b2fn%40googlegroups.com.

Wayne Warthen

unread,

Dec 18, 2025, 2:52:07 PM12/18/25

to retro-comp

Hi Marc,

I don't see anything wrong with the procedure you are using. I ran through the same steps and it seemed to work fine -- see below.

Since you have tried multiple SD Cards already, I am very surprised by this problem. It might be worth trying the approach of initializing the SD Card by writing it with one of the pre-built images such as "hd1k-combo.img". It you can boot to a disk OS this way, then try reading/writing files.

Thanks, Wayne

RomWBW HBIOS v3.5.1, 2025-05-21

Small Computer SC131 [SCZ180_sc131_std] Z8S180-N @ 18.432MHz IO=0xC0
0 MEM W/S, 2 I/O W/S, INT MODE 2, Z180 MMU
512KB ROM, 512KB RAM, HEAP=0x4E3F
ROM VERIFY: 00 00 00 00 PASS

ASCI0: IO=0xC0 ASCI W/BRG MODE=115200,8,N,1
ASCI1: IO=0xC1 ASCI W/BRG MODE=115200,8,N,1
INTRTC: Wed 2020-01-01 00:00:00
MD: UNITS=2 ROMDISK=384KB RAMDISK=256KB
SD: MODE=SC OPR=0x0C CNTR=0xCA TRDR=0xCB DEVICES=1
SD0: SDXC NAME=SL64G BLOCKS=0x076F5000 SIZE=60906MB

Unit Device Type Capacity/Mode
---------- ---------- ---------------- --------------------
Char 0 ASCI0: RS-232 115200,8,N,1
Char 1 ASCI1: RS-232 115200,8,N,1
Disk 0 MD0: RAM Disk 256KB,LBA
Disk 1 MD1: ROM Disk 384KB,LBA
Disk 2 SD0: SD Card 60906MB,LBA

Small Computer SC131 [SCZ180_sc131_std] Boot Loader

Boot [H=Help]: c

Loading CP/M 2.2...

CBIOS v3.5.1 [WBW]

Configuring Drives...

A:=MD0:0
B:=MD1:0
C:=SD0:0
D:=SD0:1
E:=SD0:2
F:=SD0:3
G:=SD0:4
H:=SD0:5
I:=SD0:6
J:=SD0:7

1859 Disk Buffer Bytes Free

CP/M-80 v2.2, 54.0K TPA

B>fdisk80

FDISK80 for RomWBW, UNA, Mini-M68k, KISS-68030, SBC-188 ----
Version 1.1-23 created 3-June-2023
(Running under RomWBW HBIOS)

HBIOS unit number [0..2]: 2

Capacity of disk 2: ( 59G) 124735488 Geom 6f501010

Nr ---Type- A -- Start End LBA start LBA count Size

1 FAT32 0b 260:0:1 1023:15:16 66560 124668928 59G

2 00 *** empty ***
3 00 *** empty ***
4 00 *** empty ***
Reserved 4 x 8Mb CP/M slices

>>i
>>r

Reserve how many CP/M slices (256 max.) [8]: 4
4 CP/M slices have been reserved

>>n

New partition number: 1
Starting Cylinder (default 260):
Ending Cylinder (or Size= "+nnn"): +500M
>>t
Change type of partition number: 1
New type (in hex), "L" lists types: 0b
>>p
Nr ---Type- A -- Start End LBA start LBA count Size

1 FAT32 0b 260:0:1 1023:15:16 66560 124668928 59G

2 00 *** empty ***
3 00 *** empty ***
4 00 *** empty ***
Reserved 4 x 8Mb CP/M slices

>>w
Do you really want to write to disk? [N/y]: y
Okay
FDISK exit.

B>^C
B>clrdir c: -y
CLRDIR Version 1.2b May 2024 by Max Scane

Directory cleared.
B>clrdir d: -y
CLRDIR Version 1.2b May 2024 by Max Scane

Directory cleared.
B>clrdir e: -y
CLRDIR Version 1.2b May 2024 by Max Scane

Directory cleared.
B>clrdir f: -y
CLRDIR Version 1.2b May 2024 by Max Scane

Directory cleared.

B>pip c:=b:stat.com[v]

B>dir c:
C: STAT COM
B>c:stat
A: R/W, Space: 248k
B: R/W, Space: 22k
C: R/W, Space: 8168k

B>

MarcK

unread,

Dec 19, 2025, 3:10:57 PM12/19/25

to retro-comp

Hello Wayne,

Thank you for your response!

As building the SC131 requires bending and cutting the pins of the SD card module I guess this is a likely source of error. I have ordered a replacement and will report back my findings.

Thanks,

Marc

Op donderdag 18 december 2025 om 20:52:07 UTC+1 schreef Wayne Warthen:

Mark Pruden

unread,

Dec 19, 2025, 11:12:38 PM12/19/25

to retro-comp

Hi Marc

Since you are new to this, you might want to consider using the Modern hd1k hard disk layout, it has several advantages over the classic layout, and is generally considered the better, unless you have a specific reason of course.

Also is there a reason for reserving only 4 slices (32mb), this is not very many and quite limiting. Also anything less than 8 is problematic as (by default) RomWBW will assign the first 8 slices at startup. The combo images reserve 512mb (64 slices) that is considered a good amount for a 1gb card.

It would be useful for you to post the complete startup messages including the boot of CPM, this might help understand any issues. Another useful command is `assign` for listing the drive mappings, which potentially could be part of the issue.

Mark.

MarcK

unread,

Dec 23, 2025, 2:48:39 PM12/23/25

to retro-comp

Hello Wayne,

thanks for your help. Unfortunately replacing the SD card adaptor with a brand new one didn't solve the problem.

A pip b:=c:stat.com[v] aborts whereas omitting the [v] option gives an unusable stat.com executable.

Executing and comparing the B-drive (ramdisk) with the C-drive (slice on the SD-card) shows:

B>stat b:dsk:

B: Drive Characteristics

3072: 128 Byte Record Capacity

384: Kilobyte Drive Capacity

256: 32 Byte Directory Entries

0: Checked Directory Entries

256: Records/ Extent

16: Records/ Block

64: Sectors/ Track

0: Reserved Tracks

B>stat c:dsk:

C: Drive Characteristics

65408: 128 Byte Record Capacity

8176: Kilobyte Drive Capacity

1024: 32 Byte Directory Entries

0: Checked Directory Entries

256: Records/ Extent

32: Records/ Block

64: Sectors/ Track

2: Reserved Tracks

For me the differences completely correct.

Even initialisation with a Windows 11 diskutil didn't solve the issue.

Looking at the quality of my soldering (compared what I saw on the internet) that might be an alternative error source. I will redouble check again and again ...

Thanks anyway!

Regards,

Marc

Op donderdag 18 december 2025 om 20:52:07 UTC+1 schreef Wayne Warthen:

Hi Marc,

MarcK

unread,

Dec 23, 2025, 3:01:28 PM12/23/25

to retro-comp

Hello Mark,

I followed your advice and went on for the modern partitioning approach. The end result was identical. Here is a screenshot of the initial start-up:

RomWBW HBIOS v3.5.1, 2025-05-21

Small Computer SC131 [SCZ180_sc131_std] Z8S180-N @ 18.432MHz IO=0xC0

0 MEM W/S, 2 I/O W/S, INT MODE 2, Z180 MMU

512KB ROM, 512KB RAM, HEAP=0x4E3F

ROM VERIFY: 00 00 00 00 PASS

ASCI0: IO=0xC0 ASCI W/BRG MODE=115200,8,N,1

ASCI1: IO=0xC1 ASCI W/BRG MODE=115200,8,N,1

INTRTC: Wed 2020-01-01 00:00:00

MD: UNITS=2 ROMDISK=384KB RAMDISK=256KB

SD: MODE=SC OPR=0x0C CNTR=0xCA TRDR=0xCB DEVICES=1

SD0: SDHC NAME=SD16G BLOCKS=0x01CF6000 SIZE=14828MB

Unit Device Type Capacity/Mode

---------- ---------- ---------------- --------------------

Char 0 ASCI0: RS-232 115200,8,N,1

Char 1 ASCI1: RS-232 115200,8,N,1

Disk 0 MD0: RAM Disk 256KB,LBA

Disk 1 MD1: ROM Disk 384KB,LBA

Disk 2 SD0: SD Card 14828MB,LBA

Small Computer SC131 [SCZ180_sc131_std] Boot Loader

Boot [H=Help]: C

Loading CP/M 2.2...

CBIOS v3.5.1 [WBW]

Configuring Drives...

A:=MD0:0

B:=MD1:0

C:=SD0:0

D:=SD0:1

E:=SD0:2

F:=SD0:3

G:=SD0:4

H:=SD0:5

I:=SD0:6

J:=SD0:7

1859 Disk Buffer Bytes Free

CP/M-80 v2.2, 54.0K TPA

Here I do not see any issue. Rom check-sum is ok. Wait-states are as expected.

One strange observation, after the reboot the partitioning info was gone! See

Small Computer SC131 [SCZ180_sc131_std] Boot Loader

Boot [H=Help]: C

Loading CP/M 2.2...

CBIOS v3.5.1 [WBW]

Configuring Drives...

A:=MD0:0

B:=MD1:0

C:=SD0:0

D:=SD0:1

E:=SD0:2

F:=SD0:3

G:=SD0:4

H:=SD0:5

I:=SD0:6

J:=SD0:7

1859 Disk Buffer Bytes Free

CP/M-80 v2.2, 54.0K TPA

B>fdisk80

FDISK80 for RomWBW, UNA, Mini-M68k, KISS-68030, SBC-188 ----

Version 1.1-23 created 3-June-2023

(Running under RomWBW HBIOS)

HBIOS unit number [0..2]: 2

Capacity of disk 2: ( 14G) 30367744 Geom cf601010

Nr ---Type- A -- Start End LBA start LBA count Size

1 ?? * ff1023:255:63 1023:255:63 4294967295 4294967295 2T

2 ?? * ff1023:255:63 1023:255:63 4294967295 4294967295 2T

3 ?? * ff1023:255:63 1023:255:63 4294967295 4294967295 2T

4 ?? * ff1023:255:63 1023:255:63 4294967295 4294967295 2T

Any thoughts?

Thanks,

Marc

Op zaterdag 20 december 2025 om 05:12:38 UTC+1 schreef mark....@gmail.com:

MarcK

unread,

Dec 23, 2025, 3:06:50 PM12/23/25

to retro-comp

Oh ... I just had a thought that the SD card reader might have an issue with its power. But I measure a 5,16V between GND and VCC on the SD card board. That looks like a very acceptable value to me.

Op dinsdag 23 december 2025 om 21:01:28 UTC+1 schreef MarcK:

Reply all

Reply to author

Forward