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.
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