Hi folks, I'm cross-posting this from the CSIPH FB group, as I'm not a huge fan of Facebook for long-form discussion.

I recently picked up _eight_ of these iomega PC4B50 MCA cards. They're in excellent condition, but very poorly documented in the modern era. Has anyone personally ever used one of these, back in the day? They're circa-1989, and I'd like to offer anybody who wants one a crack at getting these to work with a modern SCSI emulation adapter, such as ZuluSCSI, SCSI2SD, or other such SCSI-2 compliant SCSI emulator.

Since these SCSI emulators have user-configurable device, manufacturer, and version ID strings, it should be possible to lie to the HBA about it being one or more of the supported model types.

According to the available documentation at ardent-tool, "The PC4B controller supports the following Iomega drive subsystems: Bernoulli 230, MultiDisk 150, Bernoulli 90, Bernoulli 44, Bernoulli, Floptical 21, LaserSafe, and LaserSafe PRO"

The only device on the list above that I have currently is the MultiDisk 150, so that's where I'll start. Short of removing the MultiDisk 150 from its external enclosure, however, I can't easily attach it to the rear-facing DB37 connector, without fashioning my own cable, which is a PITA.

As there are seemingly no high-quality photos of the card, I took a couple, one of the top of the PCB, and another of the bottom, which you can see here:

Top - https://i.imgur.com/YSSciNw.jpg
Bottom - https://i.imgur.com/v976U07.jpg

I'm guessing that the NCR IC at U7, which is labeled 0114800, is a custom variant of a standard NCR SCSI controller, such as the 53C400, but that's just an educated guess.

Regards,
Alex Perez

Looks to be J6 / CR1 provides TERMPWR.

Anyone got the BIOS? 27C64A-25, nothing special.

On 6/4/2022 15:07, ape...@alexperez.com wrote:
> Top -https://i.imgur.com/YSSciNw.jpg

On Saturday, June 4, 2022 at 2:07:27 PM UTC-7, Louis Ohland wrote:
> Looks to be J6 / CR1 provides TERMPWR.
>
> Anyone got the BIOS? 27C64A-25, nothing special.

I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.

Huh, what? EEPROMs or OTPs, that would be sordid understandable.

Can you provide the dump to MAJ Tom or "The Beem[er]"

On 6/5/2022 12:09, ape...@alexperez.com wrote:
> I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.

https://datasheet.datasheetarchive.com/originals/scans/Scans-006/Scans-00139417.pdf

Not seeing security, fuse, or encryption.

On 6/5/2022 12:40, Louis Ohland wrote:
> https://datasheet.datasheetarchive.com/originals/scans/Scans-006/Scans-00139417.pdf
>

On Sunday, June 5, 2022 at 10:35:07 AM UTC-7, Louis Ohland wrote:
> Huh, what? EEPROMs or OTPs, that would be sordid understandable.
>
> Can you provide the dump to MAJ Tom or "The Beem[er]"
> On 6/5/2022 12:09, Alex Perez wrote:
> > I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.

I stuck it at http://scsi2sd.com/iomega-pc4b50-v6.21-rom.bin

> > > I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.
> I stuck it at http://scsi2sd.com/iomega-pc4b50-v6.21-rom.bin

Looks fine to me - I'll compare the version to what I have.

Dave, how could Iomega restrict the PC4B to [I assume] removable drives?
FUD, or just missing SCSI commands?

On 6/6/2022 19:25, IBMMuseum wrote:
>>>> I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.
>> I stuck it at http://scsi2sd.com/iomega-pc4b50-v6.21-rom.bin
>
> Looks fine to me - I'll compare the version to what I have.

On Monday, June 6, 2022 at 5:55:53 PM UTC-7, Louis Ohland wrote:
> Dave, how could Iomega restrict the PC4B to [I assume] removable drives?
> FUD, or just missing SCSI commands?
> On 6/6/2022 19:25, IBMMuseum wrote:
> >>>> I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.
> >> I stuck it at http://scsi2sd.com/iomega-pc4b50-v6.21-rom.bin
> >
> > Looks fine to me - I'll compare the version to what I have.

The easiest place to do this would probably be in the driver, but given that it appears they're using a custom ASIC, possibly just a customized PLCC 53C400 (It's NCR-branded, after all) the controller itself could easily limit it to working with a whitelist of SCSI devices, which only return approved SCSI device/vendor/versions strings, and possibly also a custom SCSI Mode Page.

I've got an earlier 'PC4' (no 'B') as well - with no ROM.

There seems to be PC4, PC4A, PC4B. My attempts to dig up ad copy failed.
IA picks up www.iomega.com late '96 [IIRC], by then the PC4n was no
longer active? can't see it in the Products section...

On 6/6/2022 22:38, IBMMuseum wrote:
> I've got an earlier 'PC4' (no 'B') as well - with no ROM.

PC3B XT / AT
PC4B 50 / 60 / 80

On 6/7/2022 06:08, Louis Ohland wrote:
> There seems to be PC4, PC4A, PC4B. My attempts to dig up ad copy failed.
> IA picks up www.iomega.com late '96 [IIRC], by then the PC4n was no
> longer active? can't see it in the Products section...
>
> On 6/6/2022 22:38, IBMMuseum wrote:
>> I've got an earlier 'PC4' (no 'B') as well - with no ROM.
>

https://www.amazon.com/Iomega-IOMEGA-PC4-ADAPTER/dp/B00456SMBE

On 6/7/2022 06:15, Louis Ohland wrote:
> PC3B XT / AT
> PC4B 50 / 60 / 80

Full length, 16-bit card, left third has a buncha non populated
positions. Uses NCR 53C90. No BIOS chip, GAL / PAL? Three soldered
Resistor networks. No apparent jumpers. 50 pin shrouded internal header,
DB37 external header.

My SWAG, the PC4B used a variant of 53C90 ?

Silkscreen upper right, "IOMEGA PC4 BD#2

Adapter PC4
0068300-0
03-15-1988

FCCID: DDX7EBPC4

>
> On 6/7/2022 06:08, Louis Ohland wrote:
>> There seems to be PC4, PC4A, PC4B. My attempts to dig up ad copy
>> failed. IA picks up www.iomega.com late '96 [IIRC], by then the PC4n
>> was no longer active? can't see it in the Products section...
>>
>> On 6/6/2022 22:38, IBMMuseum wrote:
>>> I've got an earlier 'PC4' (no 'B') as well - with no ROM.
>>
>

@7FF9.ADF - IOMEGA PC4 Host Adapter Board
http://www.mcamafia.de/mcapage0/adf/@7ff9.adf

Comes in full length, possumbly there is a "BD#1" or just a PC4 without
any "BD"

@7FFA.ADF - Iomega PC4B/50 SCSI Host Adapter Board
http://www.mcamafia.de/mcapage0/adf/@7ffa.adf

Comes as full length with no components on left half, all components
resemble short card, -OR- short card

On 6/7/2022 06:45, Louis Ohland wrote:
> https://www.amazon.com/Iomega-IOMEGA-PC4-ADAPTER/dp/B00456SMBE
>
> On 6/7/2022 06:15, Louis Ohland wrote:
>> PC3B XT / AT
>> PC4B 50 / 60 / 80
>
> Full length, 16-bit card, left third has a buncha non populated
> positions. Uses NCR 53C90. No BIOS chip, GAL / PAL? Three soldered
> Resistor networks. No apparent jumpers. 50 pin shrouded internal header,
> DB37 external header.
>
> My SWAG, the PC4B used a variant of 53C90 ?
>
> Silkscreen upper right, "IOMEGA PC4 BD#2
>
> Adapter PC4
> 0068300-0
> 03-15-1988
>
> FCCID: DDX7EBPC4
>
>
>
>>
>> On 6/7/2022 06:08, Louis Ohland wrote:
>>> There seems to be PC4, PC4A, PC4B. My attempts to dig up ad copy
>>> failed. IA picks up www.iomega.com late '96 [IIRC], by then the PC4n
>>> was no longer active? can't see it in the Products section...
>>>
>>> On 6/6/2022 22:38, IBMMuseum wrote:
>>>> I've got an earlier 'PC4' (no 'B') as well - with no ROM.
>>>
>>
>

https://books.google.com/books?id=ObYblXvjuhUC&pg=PA267&lpg=PA267&dq=iomega+pc4&source=bl&ots=auhC1ouMEg&sig=ACfU3U3I2AjFo1ZD-Lor4-70BCNgDApnmw&hl=en&sa=X&ved=2ahUKEwim7oCCpZv4AhVJtoQIHSU9Avs4KBDoAXoECA8QAw#v=onepage&q=iomega%20pc4&f=false

Interfaces

PC2 PC, XT, AT
PC2B Bootable
PC3B Non-Networking
PC4 PS/2 Microchannel

Methinks a better search term is "Bernoulli Box", might bring up better
hits in the 1987-1990 era.

On 6/7/2022 06:45, Louis Ohland wrote:
> https://www.amazon.com/Iomega-IOMEGA-PC4-ADAPTER/dp/B00456SMBE
>
> On 6/7/2022 06:15, Louis Ohland wrote:
>> PC3B XT / AT
>> PC4B 50 / 60 / 80
>
> Full length, 16-bit card, left third has a buncha non populated
> positions. Uses NCR 53C90. No BIOS chip, GAL / PAL? Three soldered
> Resistor networks. No apparent jumpers. 50 pin shrouded internal header,
> DB37 external header.
>
> My SWAG, the PC4B used a variant of 53C90 ?
>
> Silkscreen upper right, "IOMEGA PC4 BD#2
>
> Adapter PC4
> 0068300-0
> 03-15-1988
>
> FCCID: DDX7EBPC4
>
>
>
>>
>> On 6/7/2022 06:08, Louis Ohland wrote:
>>> There seems to be PC4, PC4A, PC4B. My attempts to dig up ad copy
>>> failed. IA picks up www.iomega.com late '96 [IIRC], by then the PC4n
>>> was no longer active? can't see it in the Products section...
>>>
>>> On 6/6/2022 22:38, IBMMuseum wrote:
>>>> I've got an earlier 'PC4' (no 'B') as well - with no ROM.
>>>
>>
>

https://webcache.googleusercontent.com/search?q=cache:NsYzJJWQsccJ:https://www.hoa.org/blog/jack-allweiss/the-iomega-host-adapter-project/+&cd=17&hl=en&ct=clnk&gl=us

On 6/7/2022 06:45, Louis Ohland wrote:
> https://www.amazon.com/Iomega-IOMEGA-PC4-ADAPTER/dp/B00456SMBE
>
> On 6/7/2022 06:15, Louis Ohland wrote:
>> PC3B XT / AT
>> PC4B 50 / 60 / 80
>
> Full length, 16-bit card, left third has a buncha non populated
> positions. Uses NCR 53C90. No BIOS chip, GAL / PAL? Three soldered
> Resistor networks. No apparent jumpers. 50 pin shrouded internal header,
> DB37 external header.
>
> My SWAG, the PC4B used a variant of 53C90 ?
>
> Silkscreen upper right, "IOMEGA PC4 BD#2
>
> Adapter PC4
> 0068300-0
> 03-15-1988
>
> FCCID: DDX7EBPC4
>
>
>
>>
>> On 6/7/2022 06:08, Louis Ohland wrote:
>>> There seems to be PC4, PC4A, PC4B. My attempts to dig up ad copy
>>> failed. IA picks up www.iomega.com late '96 [IIRC], by then the PC4n
>>> was no longer active? can't see it in the Products section...
>>>
>>> On 6/6/2022 22:38, IBMMuseum wrote:
>>>> I've got an earlier 'PC4' (no 'B') as well - with no ROM.
>>>
>>
>

Wading through the hits. Windows KB article mentions the PCn and how it
didn't respond to BIOS calls, as it used INT 25h, and it needed drivers.
Let me surf...

On 6/7/2022 06:45, Louis Ohland wrote:
> https://www.amazon.com/Iomega-IOMEGA-PC4-ADAPTER/dp/B00456SMBE
>
> On 6/7/2022 06:15, Louis Ohland wrote:
>> PC3B XT / AT
>> PC4B 50 / 60 / 80
>
> Full length, 16-bit card, left third has a buncha non populated
> positions. Uses NCR 53C90. No BIOS chip, GAL / PAL? Three soldered
> Resistor networks. No apparent jumpers. 50 pin shrouded internal header,
> DB37 external header.
>
> My SWAG, the PC4B used a variant of 53C90 ?
>
> Silkscreen upper right, "IOMEGA PC4 BD#2
>
> Adapter PC4
> 0068300-0
> 03-15-1988
>
> FCCID: DDX7EBPC4
>
>
>
>>
>> On 6/7/2022 06:08, Louis Ohland wrote:
>>> There seems to be PC4, PC4A, PC4B. My attempts to dig up ad copy
>>> failed. IA picks up www.iomega.com late '96 [IIRC], by then the PC4n
>>> was no longer active? can't see it in the Products section...
>>>
>>> On 6/6/2022 22:38, IBMMuseum wrote:
>>>> I've got an earlier 'PC4' (no 'B') as well - with no ROM.
>>>
>>
>

http://www.cs.ubbcluj.ro/~forest/HtmlFolder/AC/NG/ng79205.html

On 6/7/2022 07:51, Louis Ohland wrote:
> Wading through the hits. Windows KB article mentions the PCn and how it
> didn't respond to BIOS calls, as it used INT 25h, and it needed drivers.
> Let me surf...
>
> On 6/7/2022 06:45, Louis Ohland wrote:
>> https://www.amazon.com/Iomega-IOMEGA-PC4-ADAPTER/dp/B00456SMBE
>>
>> On 6/7/2022 06:15, Louis Ohland wrote:
>>> PC3B XT / AT
>>> PC4B 50 / 60 / 80
>>
>> Full length, 16-bit card, left third has a buncha non populated
>> positions. Uses NCR 53C90. No BIOS chip, GAL / PAL? Three soldered
>> Resistor networks. No apparent jumpers. 50 pin shrouded internal
>> header, DB37 external header.
>>
>> My SWAG, the PC4B used a variant of 53C90 ?
>>
>> Silkscreen upper right, "IOMEGA PC4 BD#2
>>
>> Adapter PC4
>> 0068300-0
>> 03-15-1988
>>
>> FCCID: DDX7EBPC4
>>
>>
>>
>>>
>>> On 6/7/2022 06:08, Louis Ohland wrote:
>>>> There seems to be PC4, PC4A, PC4B. My attempts to dig up ad copy
>>>> failed. IA picks up www.iomega.com late '96 [IIRC], by then the PC4n
>>>> was no longer active? can't see it in the Products section...
>>>>
>>>> On 6/6/2022 22:38, IBMMuseum wrote:
>>>>> I've got an earlier 'PC4' (no 'B') as well - with no ROM.
>>>>
>>>
>>
>

07FF9h "IOMEGA PC4 Host Adapter Board"

NumBytes 2

"I/O Address Select"
Use any one of the I/O Addresses listed
"240" [00240-0025F], 340 [00340-0035F], 400 [00400-0041F], 420
[00420-0043F], 3240 [03240-0325F], 8240 [08240-0825F], A240
[0A240-0A25F], "Disabled"

"DMA Level Select"
The PC4 supports the DMA mode of data transfer. The lower the DMA level,
the higher the corresponding priority. DMA level 5 is recommended.

"DMA Level 5", 6, 7

"Fairness"
'Fairness' enabled, the PC4 won’t compete for the channel during the
next arbitration phase if it is currently in control of the channel.
Other installed adapters can obtain the channel in the next sequence
based on each adapter's assigned priority level.
'Fairness' disabled, the adapter competes for every arbitration phase
and obtains more than its fair share of channel usage. Recommend
'Fairness Enabled' for all adapters.

"Fairness Enabled", "Fairness Disabled"

"Preempt Count Select"
When the PC4 detects that another adapter requires use of the channel,
the Preempt Count feature is activated. The Preempt Count is the maximum
number of bytes to transfer before yielding control of the channel. The
PC4 always transfers a max of 7 bytes before relinquishing control of
the channel. NOTE: Always ON, it appears...
"7 Bytes"

07FFAh "Iomega PC4B/50 SCSI Host Adapter Board"

NumBytes 4

FixedResources pos[0]=00XXXXXXb pos[1]=X11XXXXXb

"I/O Address Select"
Use any one of the I/O Addresses listed
"240" [00240-0025F], 340 [00340-0035F], 400 [00400-0041F], 420
[00420-0043F], 3240 [03240-0325F], 8240 [08240-0825F], A240
[0A240-0A25F], "Disabled"

"DMA Level Select"
The PC4 supports the DMA mode of data transfer. Most O/Ss require this
option to be enabled. Each DMA level has a corresponding priority level;
the lower the DMA level, the higher the corresponding priority. DMA
level 5 is recommended.

"DMA Level 5", 6, 7, Disabled

"Fairness"
'Fairness' enabled, PC4 won’t compete for the channel during the next
arbitration phase if it is currently in control of the channel. Other
adapters can obtain the channel in the next sequence based on each
adapter's assigned priority level.
'Fairness' disabled, PC4 competes for every arbitration phase and
obtains more than its fair share of channel usage. We recommend you use
'Fairness Enabled' for all adapters.
"Fairness Enabled", Fairness Disabled

"IRQ level”
"Operation with multi-tasking O/Ss may require an IRQ when the PC4
requires processor service. For DOS-only systems, this may be disabled.
NOTE: You cannot share IRQs between the PC4 and another adapter.
"IRQ 7", 5, 3, 9, Disabled

"Memory Address Select"
Use any Memory Address listed. "Disabled" is recommended for systems
with a fixed disk installed.
"Disabled", D400, D200, D000, CE00, CC00, CA00, C800

On 6/7/2022 06:57, Louis Ohland wrote:
> @7FF9.ADF - IOMEGA PC4 Host Adapter Board
> http://www.mcamafia.de/mcapage0/adf/@7ff9.adf
>
> Comes in full length, possumbly there is a "BD#1" or just a PC4 without
> any "BD"
>
> @7FFA.ADF - Iomega PC4B/50 SCSI Host Adapter Board
> http://www.mcamafia.de/mcapage0/adf/@7ffa.adf
>
> Comes as full length with no components on left half, all components
> resemble short card, -OR- short card
>
>
> On 6/7/2022 06:45, Louis Ohland wrote:
>> https://www.amazon.com/Iomega-IOMEGA-PC4-ADAPTER/dp/B00456SMBE
>>
>> On 6/7/2022 06:15, Louis Ohland wrote:
>>> PC3B XT / AT
>>> PC4B 50 / 60 / 80
>>
>> Full length, 16-bit card, left third has a buncha non populated
>> positions. Uses NCR 53C90. No BIOS chip, GAL / PAL? Three soldered
>> Resistor networks. No apparent jumpers. 50 pin shrouded internal
>> header, DB37 external header.
>>
>> My SWAG, the PC4B used a variant of 53C90 ?
>>
>> Silkscreen upper right, "IOMEGA PC4 BD#2
>>
>> Adapter PC4
>> 0068300-0
>> 03-15-1988
>>
>> FCCID: DDX7EBPC4
>>
>>
>>
>>>
>>> On 6/7/2022 06:08, Louis Ohland wrote:
>>>> There seems to be PC4, PC4A, PC4B. My attempts to dig up ad copy
>>>> failed. IA picks up www.iomega.com late '96 [IIRC], by then the PC4n
>>>> was no longer active? can't see it in the Products section...
>>>>
>>>> On 6/6/2022 22:38, IBMMuseum wrote:
>>>>> I've got an earlier 'PC4' (no 'B') as well - with no ROM.
>>>>
>>>
>>
>

Huh, does this mean the /50 and the HD have different ROMs, different
SCSI controllers, or "YES"

Note, they all support "Fairness", which is a requirement for BURST. My
SWAG is this is a SCSI-2 command set compatible, 5MB/s SCSI bus, roughly
8.3MB/s to MCA bus?

I think the 86C01 is a bus interface thingy...

@7FF9.ADF IOMEGA PC4 Host Adapter Board
@7FFA.ADF Iomega PC4B/50 SCSI Host Adapter Board
@5FCB.ADF Iomega PC4B/HD SCSI Host Adapter Board

07FF9h "IOMEGA PC4 Host Adapter Board"

NumBytes 2

"I/O Address Select"
Use any one of the I/O Addresses listed
"240" [00240-0025F], 340 [00340-0035F], 400 [00400-0041F], 420
[00420-0043F], 3240 [03240-0325F], 8240 [08240-0825F], A240
[0A240-0A25F], "Disabled"

"DMA Level Select"
The PC4 supports the DMA mode of data transfer. The lower the DMA level,
the higher the corresponding priority. DMA level 5 is recommended.

"DMA Level 5", 6, 7

"Fairness"
'Fairness' enabled, the PC4 won’t compete for the channel during the
next arbitration phase if it is currently in control of the channel.
Other installed adapters can obtain the channel in the next sequence
based on each adapter's assigned priority level.
'Fairness' disabled, the adapter competes for every arbitration phase
and obtains more than its fair share of channel usage. Recommend
'Fairness Enabled' for all adapters.

"Fairness Enabled", "Fairness Disabled"

"Preempt Count Select"
When the PC4 detects that another adapter requires use of the channel,
the Preempt Count feature is activated. The Preempt Count is the maximum
number of bytes to transfer before yielding control of the channel. The
PC4 always transfers a max of 7 bytes before relinquishing control of
the channel. NOTE: Always ON, it appears...
"7 Bytes"

07FFAh "Iomega PC4B/50 SCSI Host Adapter Board"

NumBytes 4

FixedResources pos[0]=00XXXXXXb pos[1]=X11XXXXXb

"I/O Address Select"
Use any one of the I/O Addresses listed
"240" [00240-0025F], 340 [00340-0035F], 400 [00400-0041F], 420
[00420-0043F], 3240 [03240-0325F], 8240 [08240-0825F], A240
[0A240-0A25F], "Disabled"

"DMA Level Select"
The PC4 supports the DMA mode of data transfer. Most O/Ss require this
option to be enabled. Each DMA level has a corresponding priority level;
the lower the DMA level, the higher the corresponding priority. DMA
level 5 is recommended.

"DMA Level 5", 6, 7, Disabled

"Fairness"
'Fairness' enabled, PC4 won’t compete for the channel during the next
arbitration phase if it is currently in control of the channel. Other
adapters can obtain the channel in the next sequence based on each
adapter's assigned priority level.
'Fairness' disabled, PC4 competes for every arbitration phase and
obtains more than its fair share of channel usage. We recommend you use
'Fairness Enabled' for all adapters.
"Fairness Enabled", Fairness Disabled

"IRQ level”
"Operation with multi-tasking O/Ss may require an IRQ when the PC4
requires processor service. For DOS-only systems, this may be disabled.
NOTE: You cannot share IRQs between the PC4 and another adapter.
"IRQ 7", 5, 3, 9, Disabled

"Memory Address Select"
Use any Memory Address listed. "Disabled" is recommended for systems
with a fixed disk installed.
"Disabled", D400, D200, D000, CE00, CC00, CA00, C800

05FCBh "Iomega PC4B/HD SCSI Host Adapter Board"

NumBytes 4

FixedResources pos[0]=00XXXXXXb pos[1]=X11XXXXXb

"I/O Address Select"
"240", 340, 400, 420, 3240, 8240, A240, Disabled
Set the adapter to any of the I/O Addresses. The first choice is
recommended. 'Disabled' causes the adapter to be inaccessible.

"DMA Level Select"
The PC4 supports DMA mode of data transfer. Most operating systems
require this option to be enabled. The lower the DMA level, the higher
the corresponding priority.
If you have a hard disk installed, it is recommended that you select a
DMA level higher than the hard disk.

"DMA Level 7", 6, 5, DMA Disabled

"Fairness"
"If 'Fairness' is enabled, the PC4 adapter will not compete for the
channel during the next arbitration phase if it is currently in control
of the channel. This allows other installed adapters to obtain the
channel in the next sequence based on each adapter's assigned priority
level. When 'Fairness' is disabled, the adapter will compete for every
arbitration phase and will obtain more than its fair share of channel
usage. We recommend you use 'Fairness Enabled' for all adapters.

"Fairness Enabled", Fairness Disabled

"IRQ level"
Operation with multi-tasking operating systems may require an IRQ when
the PC4 requires processor service. No other adapter may be assigned the
same IRQ level as the PC4. For DOS-only systems, this option may be
disabled.

IRQ 3, 5, 7, 9, or Disabled.

"Memory Address Select"
The PC4 may be set to any one of the Addresses listed. “Disabled” is
recommended for systems with a fixed disk installed. If you want to boot
from a device connected to your PC4, select the first available memory
address and assign the device attached to the adapter the SCSI ID of
zero. NOTE: Uses the clone 0,1 for boot devices !

"Disabled", DC00, D800, D400, D000, CC00, C800

"Termination Select"
Set the termination ON or OFF. Default is ON. Turn the termination OFF
if you intend to use both the internal and external connectors.

"ON", OFF

PC3B non-networking... I wonder if that means that on an XT or AT that
the PC3B takes up the DMA channel used by the networking card

On 6/7/2022 07:03, Louis Ohland wrote:
> https://books.google.com/books?id=ObYblXvjuhUC&pg=PA267&lpg=PA267&dq=iomega+pc4&source=bl&ots=auhC1ouMEg&sig=ACfU3U3I2AjFo1ZD-Lor4-70BCNgDApnmw&hl=en&sa=X&ved=2ahUKEwim7oCCpZv4AhVJtoQIHSU9Avs4KBDoAXoECA8QAw#v=onepage&q=iomega%20pc4&f=false
>
>
> Interfaces
>
> PC2 PC, XT, AT
> PC2B Bootable
> PC3B Non-Networking
> PC4 PS/2 Microchannel